My 1983 Compac 23 was bought complete with a four stroke Honda 8 hp (which is way too much power). I have an opportunity to change to an electric start 2 stroke Mercury of 7.5 hp (probably still too much power). I would prefer the Honda or better yet a smaller motor but the electric start is a plus for Nanci. Electric starts don't seem to come in smaller sizes. As there are times when getting home is looming and the wind is not cooperating, my question concerns fuel consumption. Any data on this?
I don't have any specific data to share, but generally speaking a 2 stroke motor will consume to the order or 50-100% more fuel than a 4 stroke. It depends on the prop, rpms and what motor you're using.
I actually see this as a good thing for sailboats since gas tends to not get used much. With ethanol in fuel nowadays, you MUST use fresh fuel or you'll have carb trouble in short order. Having a higher consumption motor will encourage using fresh fuel. Unless you are going to motor a lot (ie a long channel or just to make time), or go on long cruises, the higher consumption isn't going to be that big of a deal. If you're motoring 5 hours a week or more or plan to go a long ways between marinas, it probably makes sense to use a 4 stroke as you'll use the gas up before it goes bad. Otherwise I like the 2 stroke.
The mercury is really a Tohatsu (japanese=quality) branded as a Mercury. Nothing wrong with Honda...I won't use them myself as I've had a lot of trouble with their lawnmowes and generators. However a nice Honda VFR interceptor graces the garage and it's abuot as perfect as a bike can get.
Also 2 strokes weigh a whole lot less and require less maintenance at the expense of having to mix oil in the gas.
This is just my opinion, others will probably disagree with me.
I have read the fuel consumption varies as little as 10% to as high as 25%. I use the 8hp Honda on my 23. I prefer it because of noise and no smell. I don't believe the fuel savings would buy a case of beer a season since it is the auxillary power.
Bob K
If I could, I'd drive a Mazda Rotary. So smooth you don't even feel it running, but boy do they blubber out oil and fuel, Even have a rotary R/C rotary engine...way cool I can hold it in my hand and run it. And there is a diesel conversion for normal 2 stroke R/C engines too.
"10-25%? It has to be more than that?"
I'm not sure what that means?
"the fuel passages in the carburetors are larger in two stroke engines"
Why? Every time the piston comes up it's fueled and driven back down but the air/fuel mix ratio remains the same 14.7:1. Every pulse into the combustion chamber of X amount of cc's is the same. Regardless if it's a two stroke or a four stroke. Why would the fuel passages be larger, but rather 'worked' more times per minute. "Instead of every fourth time the piston comes up, every time".
"a 2 stroke motor will consume to the order or 50-100% more fuel than a 4 stroke"
True but it's making power every stroke. So why wouldn't it burn more fuel per equal running time? I fly R/C aeroplanes. Both Rossi 2 stroke and OS Max four stroke 0.40 cubic inch engines. Checked on the ground with my electronic tach...
I can turn a smaller prop and less pitch at 21,000 rpm on the ground. More rpm in the air once the prop unloads in the air on the two stroke.
I can turn a larger prop and more pitch at 10,500 rpm on the ground. More rpm in the air once the prop unloads in the air on the four stroke.
The same plane and four stroke 0.40 cu inch engine is so much more fuel efficient [22 minutes vs 9 minutes] but it is so much slower. I mean if I was just flying point to point my distance covered in nine minutes would be so much more then the distance covered in 22 minutes. It's a wash as far as energy used, X amount of distance vs X amount of fuel used is about equal. But as always resistance through air is squared as speed doubles. I wounder what is is for water?
I'm thinking when I'm really booking 14 miles across the Bay of Green Bay to the otherside my 5hp 2 cycle Mercury full open at about about 5200 rpm uses about 1/2 gallon [50:1 fuel/oil] an hour at a 5.4 knots, S.O.G. via the chartplotter. I burn about 7 to 9 gallons a season. My tank is 3 gallons.
I wonder if anyone uses a diesel O/B ? Air or water cooled.
skip.
10-25%? It has to be more than that?
Two strokes intake and combust fuel at twice the interval of 4 strokes. Also there is blowby; where as the fuel is being drawn into the combustion chamber through the intake, some unburnt fuel is expelled out the exhaust at the same time. Just the way they are designed. Less efficient.
Typically..and one would have to check this, the fuel passages in the carburators are larger in two stroke engines. This is to allow for sufficient oil/fuel mix to lubricate the engine as the primary goal with the secondary goal being to keep up with the increased demand for fuel (twice as much combustion).
With that said, my numbers were estimates and could be way off.
The reason question is how far are you planning to go between marinas?
Skip's figures match up closely with a 4hp 2 stroke Johnson I used to have. When I switched to a 3.5 4 stroke, economy went way up...about 1 quart for every hour of use at 1/2 throttle. That's about a month and half of use for me, thus my fixation on fresh fuel. Burned about 2.5 gallons all season-the lawnmower would get the old gas.
unless your local regulations have prohibited two strokes, thats the way to go for three reasons. simplicity-two strokes have no valves and the associated hardware required. reliability-as long as the fuel is pretty fresh they will run forever, and they weigh a hell of a lot less which is important on any sailboat. plus,they actually produce more power as every stroke is a power stoke and the associated mechanical rolling resitance i.e. cams etc is absent.
I agree with kickingbug on the reliability. My Nissan 8 has been incredibly reliable for the past 7 seasons.
It has never failed to start and pushes the boat well in most conditions. (Lake Huron). The prop sometimes comes out of the water in big waves. For winterizing I drain the oil and store it in a warm basement. Very simple.
I also have a 1988 Nissan 8 hp 2 stroke on my 1985 23/2. It starts every time on the first pull, even when I brought it out of winter storage. I'll never get rid of that motor. I might use 10 gallons a season. That's not too bad.
Skip: I'd heard that Yanmar was going to produce a diesel outboard but I doubt it would be small enough for the hp that we commonly use.
Salty: Trouble with Hondas? Strange. I have a generator and a powerwasher. Both perform flawlessly. Even my 1984 Accord Hatchback runs great. For fun, I borrow my brother in laws 2001 S-2000. That helps cure my need for speed. Love the 9000 rpm redline. Too bad Honda stoped importing them.
Returning to the issue, like most of you, I like the lighter weight of the 2 stroke feels better than a heavy 4 stroke back there on the transom. My mantra is "If it works, don't fix it". I'll be a Nissan 2 stroker for a long time, I hope.
Bob23
I have had a Tohatsu for 3 years and it has been not been very good. I had the discussion on the CP19 site,
but now that the carberator is tunes and clean, and I only use 93 octane fueld with Marine Stabil,
I hope things will be better . I am also excited to hear that the engine is very reliable because
when it is not reliable, it is consistently not reliable!
I also run my fuel out whenever I am done with the boat whether a day or a week to the next use..
===
I have a yanmar 12 HP in my Cape Dory and I can not beleive that they can build
a "lightweight" diesel. Yanmar makes a great diesel !
Yep, Bob--I've had no luck with Honda small engines. I know this is unusual! Will never buy one again! My generator uses oil and refuses to start sometimes (I've rebuilt the carb twice). The lawnmower is also difficult to start and has no power. Actually I gave it away to a neighbor in favor of a Toro which has been flawless.
With that said they make great cars and bikes! Have had many Honda bikes and they all have been real good. Considering a Civic Si but probably will stick with the fire-breathing MR2 turbo for awhile. If you come out, I'll have to take you for a ride in it (much quicker than an S2000).
Back to outboards, I just picked up a used, but never started Yamaha 8hp 2 stroke/2 cylinder. Should run a heck of a lot smoother than the 6hp 4 stroke. I'm not real impressed with the 4 stroke Nissans (Tohatsu). Hard to start and seems like the power of a 3-4hp motor...very sluggish and vibrates like crazy past 1/2 throttle. I'll probably hang onto it for a backup.
I also have a 1994 S2000 in mint condition with 9000 miles. (yes... 9K miless)
Never been in the rain or snow... always garaged
damn little rocket! I am thinking of selling it to reduce the toys...
hard to keep everything running well
I almost think I should knock on wood with this one. Honda tiller, Honda pressure washer, four strokes, never do anything to them leave the fuel in the tank year round, no stabil, don't use them but a couple of times a year, always start on the second pull and run perfectly.
My Suzuki 9.9 four stroke has also run perfectly. I do try to put only alcohol free gasoline in it, but not always possible. If the motor had not come with the boat, I would have a 6 or 8 hp to try to cut down the weight. I have never needed the power. Last week at BEER, when the wind did not cooperate or when approaching anchorages I ran it at about 1/4 throttle and made about 5 knots.
I do notice that there is a slight difference between the two tanks I have for it. I have a Suzuki OEM with a 5/16" fuel line, it is a 3.2 gal with a manual vent. Motor runs smooth as glass. I also have a Bombardier 6 gallon tank with a 3/8" fuel line "self venting" whatever that means. Motor tends to surge a little bit varying RPM.
Fuel consumption is not important in my world. Last year I burned about 4 gallons total.
"Back to outboards, I just picked up a used, but never started Yamaha 8hp 2 stroke/2 cylinder. Should run a heck of a lot smoother than the 6hp 4 stroke. I'm not real impressed with the 4 stroke Nissans (Tohatsu). Hard to start and seems like the power of a 3-4hp motor...very sluggish and vibrates like crazy past 1/2 throttle. I'll probably hang onto it for a backup."
Have you had the Tohatsu looked at? Doesn't sound right, esp. the vibration after 1/2 throttle.
I replaced a Johnson 8hp 2 cylinder 2 stroke with the Tohatsu SailPro 6hp 4 stroke and love the Tohatsu. Starts second pull, plenty of power, quieter, slightly lighter and will go a lot slower at idle (idle speed is about half the 2 strokes) in gear then the Johnson which is handy when docking. The only thing I really liked about the Johnson more was the front mounted shift control.
Shawn
Bob:
Before you sell your S2000, consider donating it to the Bob23 Land Travel Relief Fund. This is a worthy fund, believe me.
Salty:
A former employee bought a new Civic Si but drove it like an old lady! Some crimes deserve mandatory life sentences. It was a nice car and I couldn't help but reflect on how far the Honda car company has come. I was in the foreign car repair business when Honda released thier first cars. Total junk. Air cooled, if my memory serves me well, 10 inch wheels, and so small it made a VW beetle look like a Buick Roadmaster wagon. We had one come into our shop and it was given to me to determine why it wasn't running. How about fried pistons? yep, they were toast. I looked at that car and said to myself "This car company is going nowhere." Yeah, I have the same foresight when picking stocks.
But, lest I be accused of being a hijacker, back to outboards. I had a Tohatsu 3.5 2 stroke on my Seapearl 21, loved it and even after it was submerged in salt water (don't ask), and serviced by a good mechanic, ran like a champ and I assume continues to do so. Other than that and my current Nissan 8, I have dabled in a few old Evinrudes and Johnsons. As you all are aware of, outboard motors were created to try mens patience.
Bob23
I bought a Honda lawn mower once. No power. I sold it after one season for $15 and bought a Simplicity 6.75 hp Briggs and Straton OHV four stroke. A world of difference! Starts first pull. I liked it so much I bought a Simplicity rider with hydrostatic transmission. Another sweat ride.
skip.
Shawn-
Nope--I'm not spending any more precious time or money on it. The Yamaha will be installed real soon. After an intitial break-in at home, I'm confident it will run more smoothly and start easier. The Tohatsu will be a backup.
Dissappointing, but no worries.
The 3.5 Tohatsu 4 stroke I put on the old 16 was a much different beast. Very quiet, very smooth and started easily. It was new and I broke it in properly. I'm guessing from the sludgy oil found on the 6hp that the oil was never changed. And it may not have been broken in properly either. No matter, it's going into the basement for backup.
Face the facts. Most sailors use more fuel cutting the grass in a season than in a season of sailing. I think the main thing to worry about is being reliable. I just want the thing to start and stay running when I need it. So, I spend a few extra $$$ and have a trained person give it it's yearly check up. I'd rather have an iron Jenny than an iron paperweight. I pay a sailmaker to make and/or repair sails, even though I could take up sewing and save a few $$$. I've just learned than sometimes you need to open up the wallet and spend a little when it comes to having a boat. Yes, a two cycle may use more fuel, but my four HP Mercury two cycle runs great. I might use a bit more fuel, but we are not talking 100 gallons vs 75 gallons in a season.
Fresh gas!! Use fresh gas and the proper mix (if needed), change the spark plug and keep a spare.
On fuel consumption -- I have a 2 stroke 8 hp Evinrude on HideAway -- a 23 --- Running at 4-5 kn it will consume one gallon an hour. Its done that since the day it was new. I'd consider a switch to a 4 stroke for improved numbers only because it takes an hour to get into the Gulf if Mexico so its easy to burn two gallons a day even sailing across Boca Ciega Bay.
Can somebody compare a 23 using a 4- stroke? Matt
I have power boat friends that go through 100 gallons on a weekend.
They like to make comments about getting where they want to get to, when
they want to get there at more than 5 knots...
I tell them that I used 2 gals in the Compac and 7 gals of diesel in the Cape Dory.
The reality is it is a lifestyle and change.
... and I am looking for a bowrider to water ski and raft...
Quote from: HideAway on June 20, 2010, 05:15:03 PM
On fuel consumption -- I have a 2 stroke 8 hp Evinrude on HideAway -- a 23 --- Running at 4-5 kn it will consume one gallon an hour. Its done that since the day it was new. I'd consider a switch to a 4 stroke for improved numbers only because it takes an hour to get into the Gulf if Mexico so its easy to burn two gallons a day even sailing across Boca Ciega Bay.
Can somebody compare a 23 using a 4- stroke? Matt
My Suzuki four stroke 9.9 seems to burn about a half gallon per hour at 5 knots. Throttle is open about a third or a little less. Not sure you can get a payback on replacing a good running motor at a gallon a trip. Additionally, I don't like the extra weight and would prefer a lighter motor both for trim purposes and wear and tear on my back when mounting and dismounting for a road trip. My 23 trims down in the stern when compared to the factory waterline. I bet an inboard trims perfectly with the tank mounted a little more forward of the outboard fuel locker area.
The 9.9 will eventually end up on a Bateau FS 14 skiff on the woodshop planning board, and a lighter motor will be on the 23.
"-- I have a 2 stroke 8 hp Evinrude on HideAway -- a 23 --- Running at 4-5 kn it will consume one gallon an hour. "
My 8hp Johnson was right around there too. The 6hp Tohatsu is rated for 1/2 gallon an hour at WOT. I usually cruise at about 1/2 throttle but haven't checked fuel consumption, it is considerably better then the Johnson was though.
Speaking of the Tohatsu... it must read the forum. When I went to go out yesterday it wouldn't idle. At higher RPM it runs fine.. once I throttle back it stalls out dead. I'm assuming the low speed jet is clogged but haven't opened it up yet to check.
When I launched the week before it ran very well and started right up. I'm wondering if maybe I got a piece of fuel line into the carb from the recently plumbed in racor fuel filter. Will be opening it up to check soon.
Shawn
Shawn--lol ! I had the opposite experience just this past weekend.
I broke-in the new (1998, never started) Yamaha at home. Nice and smooth! Couldn't tell how quiet it was as I was using muffs for the water intake. Went out Sat and Sun, the Nissan (a branded Tohatsu) idled perfectly for the few minutes I used it and didn't let me down at the dock. It still vibrates quite a bit.
Must be a jealousy thing. Sorry about your issue. If you need help with the carb, read my blurb on how to clean them. Luckily your motor's carb is a breeze to work on.
That does figure doesn't it. Haven't opened the carb yet but glad to hear it is easy to work on.
For the shaking on your engine... any chance you have to much oil in the crankcase? I was doing a little searching and apparently if the Tohatsu's are overfilled it can cause rough running at higher RPMs and other issues.
Thanks,
Shawn
"I was doing a little searching and apparently if the Tohatsu's are overfilled it can cause rough running at higher RPMs and other issues."
Forgot to mention... the other issue is apparently with the wrong prop on the engine for the boat it is in. If it is too high a pitch the engine can't gets up near max RPM/HP and they apparently tend to shake in that situation too. They are supposed to top out at about 6000 RPM but in a few posts I found with the 8" or 9" pitch prop on a heavy sailboat they couldn't get up past about 3800 rpm. Moving to the high thrust 6" pitch prop helped a lot from what I read. I have the 6" pitch prop as part of the Sailpro package but I haven't measured RPM yet.
Shawn
Shawn, You raise a good point..no I have not used a tach on it to see what RPMs it turns. The prop is the standard one, I *think* it's an 8 pitch. This is one of the most overlooked things on sailboats and I'm guilty as charged. And that could well be the issue.
Oil level was correct when launched in early May. But a good idea to check it.
i guess I'll go over it real good before putting it in the crawspace to await another boat or as a spare in case the Yammie...wait...nope, not going to jinx myself :) On goes the new Yammie when hauling for the Carlyle Rendezvous in 2 weeks. I will pay close attention to the prop. Guess I'll go find a cheap tach to measure rpms...thanks for the reminder.
Had a chance to dig into the Tohatsu. The carb was very very clean inside but I opened it up and dunked it in cleaner anyway just in case.
The problem turned out to be too much oil in the crankcase. What was happening is oil was making its way up the PCV hose and back into the carb. From there it was leaning it out to much at low RPM and the oil fouled the plug. Got the oil back to the proper level (watch out for 4 strokes 'making oil' and put a new plug in. Still ran rough for a few minutes (still had some oil in the PCV hose I think) and then it cleared up and was running well again.
Regarding the prop I found a big thread on a cruising forum where a guy was having similar complaints as yours. After a couple of years he ended up trying the 6" pitch and that was the key. The factory 3 blade 6" prop is about $75 but there is an aftermarket 4 blade 5" pitch for about $35 that is supposed to fit.
Shawn
My concern about fuel consumption is because some of the places we like to go are remote enough - hard to believe in Tampa Bay area- that you cannot buy gas along the way. For instance one destination is 6 hours away one way. We all know we cannot count on good wind all the time so based on forecasted weather we usually take between 8 and 10 gallons of fuel along. A 6 gal tank and several three gallon tanks filled to 2 gal capacity. That's is a lot of weight and takes up space not to mention being a floating bomb. It would make sense to me to convert from something that runs at a gallon an hour to a quarter of that when the time comes to replace Mr E.
The wild card in this is the increased power of the loose footed main may save us a few gallons consumption. Lets hope Matt
Shawn said:
I have the 6" pitch prop as part of the Sailpro package but I haven't measured RPM yet.
Shawn, does your sail pro have the 25" shaft? Can you get it out of the water at full up and tilt on a starboard tack? are you generally happy with the performance? Does it have decompression for start? Fairly easy to start manually?
Yesterday I ordered plans for a Bateau 14' planing skiff to be built stitch and glue, composite. I think that will be the permanent home for the 9.9 hp four stroke Suzuki 20" shaft motor that is on the 23 and I'm inclined to replace it with a Tohatsu 6HP sail pro. The Suzuki runs perfectly but it is just too heavy at 104 lbs. I took a road trip recently where I had to retrieve/launch three times and each time I had to remove that beast for travel. Forces me to unhook the trailer, back the truck around to the stern, stand in the bed and hope someone comes along who can help me lift it either on or off then re-hook the trailer. I can just barely lift it the six inches myself but then my back suffers for a while. A 60 lb. motor should make all the difference in the world.
Initially I had planned to swap the 9.9 back and forth between the boats, but that is just not practical.
We use the main halyard and a harness that holds on to the motor. It takes two people though - It does save the back Matt
Yes, it is the 25" shaft and it will come completely out of the water when the bracket is up and tilted. At max tilt it is almost horizontal. One thing that takes a little getting use to is you have to put it in forward to tilt it. Which means when you lower it and go to start it it is in gear and locks out the recoil starter. After a couple times you will remember to put it in neutral after putting it back down.
Very easy to start manually. Typically it is 2 pulls. The first pull seems like nothing is happening... second pull it purrs to life. This year it has also been starting on the first pull.
I have been very happy with the performance, it has plenty of power to get the 23 to hull speed with power in reserve. It will also idle along very slowly in gear which is great for docking.
The friction adjustment for the steering is on the back of the engine and is a little hard to reach it to adjust it while underway. I get in/out of the slip steering with the engine and then lock it and use the rudder for the rest of the trip in/out of harbor. One really nice thing is the tiller on the Tohatsu is short and doesn't hit the stanchions which is good.
Just don't overfill them with oil... they don't like that. :) Other then last weekend (which was my fault) it has been a flawless runner and I am very happy with that purchase.
Shawn
BTW... looks like Defender has the Sailpros on sale right now. I bought mine from them last year.
Shawn
Hidaway,
DO you know where on the throttle gives you the most efficiency?
Your displacement hull wil only go so fast based on physics so if you
apply more throttle when you reach that point, you are just stressing the
boat and wasting gas.
To find that point, us a GPS (because of its accuracy), calculate the
max speed of the hull (don't have the formula handy but is based on water line length),
find a calm day and start with low throttle and once you get to about 90% of the calculated
speed, mark your throttle hande and that is your best efficiency. More throttle will not make the
boat go any faster.
In planning, you calculate your gas to 1/3 to destination, 1/3 back to home and 1/3 spare.
I built a 9.6 foot shellback (Wooden boat for plans) and very happy with it. I do have a 4HP motor for the back and it works great!
Quote from: HideAway on June 25, 2010, 05:23:50 PM
We use the main halyard and a harness that holds on to the motor. It takes two people though - It does save the back Matt
A good idea Matt and I've considered other possibilities such as removable jib booms with the vang as the lift mechanism, however, I've concluded that swapping the motor back and forth between boats is not practical so I might as well get a motor that is just right for the 23 and the 9.9 which I think will be just right for the skiff can go there permanently. Can't imagine needing more HP than 6 for the sailboat with a high thrust prop and XL shaft. The only thing I'm giving up is electric start.
Had a Columbia 24 challenger, 4800 lbs displacement and powered it with a 6 or sometimes a 4, both two cycles and I never lacked for power to get the job done. Motor weight was extremely important with that because it was lazarette mounted and to sail properly you had to lift it in the lazarette and put in a profile plug. That's why we used the four most of the time, easier on the back.
Additionally, I plan to make a lot of road trips. Although the mast raising/lowering part only takes twenty minutes, it currently takes me a total of 2.5 to 3 hours each way to set the boat up to launch or set it up to travel after retrieve working by myself. It's hard work and I want to cut down both the time and effort. I can "clean and jerk" the 59 lb motor by myself without having to disconnect the trailer and truck and re-hook the start power. I figure I can save 25-30 minutes with that change alone. I'm going to Kaizen the rest of the process to see what else I can streamline. Like to get it down to an easy hour or hour and a half.
So the schedule is build the skiff, verify the 9.9 is right for it, (specs. say it will plane and do 23 mph with a 600 lb. load with a 9.9 at WOT) then get the sail pro for the 23.
Quote from: HideAway on June 25, 2010, 02:56:53 PM
My concern about fuel consumption is because some of the places we like to go are remote enough - hard to believe in Tampa Bay area- that you cannot buy gas along the way. For instance one destination is 6 hours away one way. We all know we cannot count on good wind all the time so based on forecasted weather we usually take between 8 and 10 gallons of fuel along. A 6 gal tank and several three gallon tanks filled to 2 gal capacity. That's is a lot of weight and takes up space not to mention being a floating bomb. It would make sense to me to convert from something that runs at a gallon an hour to a quarter of that when the time comes to replace Mr E.
The wild card in this is the increased power of the loose footed main may save us a few gallons consumption. Lets hope Matt
Now I understand your concern. To go from Bay Springs Lake to Pickwick Lake I have to run 45 miles through Divide Cut, part of the man made Tenn Tom systems and it is truly a ditch with no opportunities for fuel along the way. I'd be in trouble if I was burning a gallon an hour. Making that trip early August.
"I can "clean and jerk" the 59 lb motor by myself without having to disconnect the trailer and truck and re-hook the start power. "
That is how I mount the Tohatsu. Just lower the mount as low as it goes and lift the engine up to the mount from the ground. It helps that I'm 6'5" though. I've also mounted/unmounted it hanging over the stanchion when it is in the water. That is a little more difficult though.
Shawn
DO you know where on the throttle gives you the most efficiency?
Bob, I watch the gps as well as the bow and stern waves to stay in the groove as it were. The Evinrude 8 has a long shaft but not a high torque. With the strong tides we experience in the passes I want as much power as I can get. With the current prop it means higher rpms Matt