News:

Howdy, Com-Pac'ers!
Hope you'll find the Forum to be both a good resource and
a place to make sailing friends.
Jump on in and have fun, folks! :)
- CaptK, Crewdog Barque, and your friendly CPYOA Moderators

Main Menu

Will Using A 60 Pound Outboard Damage The Transom

Started by geeman, June 02, 2019, 11:43:26 AM

Previous topic - Next topic

geeman

I'm a first time boat owner of a new to me 78 C16.  I found a second hand  Yamaha F4 at a good price and bought it.  It weighs about 60 lbs with the tank empty.  I looked though past posts about outboard power and weight but didn't see much written about whether something like adding an oversized backing plate behind the motor mount would be needed?  My main concern is that putting that much weight on the end of a lever on a transom likely not designed for it will deform/damage the transom over time and use.  Thanks for any info.
1978 Com-Pac 16
Hull Number 558

Bramble

With proper backing, the stern should be able to handle that weight.  A concern is that some C-16's from the seventies (I'm not sure of the exact year models) are wood cored.  If your's is one of those, any deterioration in the core (i.e. rot) would make it weaker.
With the standard motor mount, I don't think that the springs would be strong enough to assist in lifting and lowering the engine.  Without a heavy duty motor mount leaning over the stern raising & lowering 60 lbs. would not be fun. 
mike


geeman

Thanks for the input Bramble.  When you say "proper backing" do you mean additional or that which is existing?  The mount looks to be original install (I'm assuming they shipped with them.) I haven't spent anytime yet tapping on the transom to try and figure out if it is sound, but I'll certainly be doing that before clamping the motor to the lift.
1978 Com-Pac 16
Hull Number 558

MHardy

Take this for what it's worth, as I am no expert on this issue. I suspect the boat will hold the motor just fine. That isn't the issue. The real problem is that much weight aft adversely impacting the pointing performance of the boat. When I sailed my 16, we always moved forward in the cockpit when sailing upwind. I had a Honda 2hp, weighing about 30 pounds.
Seagull II, 1987 CP 27
Seagull, 1983 CP 16
Washington, North Carolina

Bramble

geeman,
often motor mounts are through-bolted with only a large washer on the inside.  A solid backing plate of wood or metal distributes the load over a larger area. 
I second what MHarday wrote.  60 pounds on the stern will cause issues with trim.

mike

geeman

MHardy and Bramble - thanks for your input.  I wonder if loading 30 pounds or so of weight in the bow area would take care of the trim issue.  Thirty pounds of sandbags fit in a pretty small area and aren't likely to shift far even if I rock and roll abit.  Is this a dangerous or stupid idea?
1978 Com-Pac 16
Hull Number 558

Bramble

I don't think that it is either stupid or dangerous, but I'm not that knowledgeable regarding trim issues, so I defer to those more experienced than me to weigh in on the issue.
mike

geeman

Today I checked the transom and the attachment of the motor mount.  The transom appears to be solid fiberglass about 1/4 inch thick.  The motor mount is through bolted with 6 bolts.  There is an aluminum backer plate approximately 8 inches square.  It does not appear to be laminated to the transom, but the whole of the thing seems sturdy.  Is there a way to determine what the transom will support at the point that the mount is attached?  I'm sure there is a way to calculate this, but don't know how.
1978 Com-Pac 16
Hull Number 558

Bramble

geeman
that sounds like a very good mounting.
Your stern should handle that weight
mike

geeman

Thanks Bramble.  Gonna remove the mount in the next couple of days, re bed and remount it after testing to see how the mount itself handles the raising of the motor.  It presently has one spring attached around the lower pivot.  I have another spring and it seems to me that if I add it to the upper pivot, it should increase the amount of weight the mount will lift.  Might not need to do anything, the mount seems pretty stiff when I raise and lower it by hand.
1978 Com-Pac 16
Hull Number 558

captronr

I plan to toss a couple cases of water bottles in the bow to counter my weight and the 55# motor.

Easy to install and remove for winter.
Ron
"When the world ends, I want to be in KANSAS, because its 20 years behind the times."  Plagarized from Mark Twain

geeman

#11
Good thought.  How does your 55 pound motor effect your sailing/boat trim?  And sounds like the weight on your tramsom is not an issue from a structural standpoint?
1978 Com-Pac 16
Hull Number 558

captronr

Geeman, my personal ballast has much more effect on trim than the motor (LOL).
"When the world ends, I want to be in KANSAS, because its 20 years behind the times."  Plagarized from Mark Twain

Eric

Our first Compac 16 had oars , one day the engine wouldn't start so we pulled the engine and fuel tank off the boat and oared the boat out of the marina ,  it was suprising how much nicer the boat sailed without that weight .
1998 CP 16 CB

geeman

If I could find a ramp that was lightly used so as not to be in the way when trying to launch and load I would like to try sailing without auxiliary power, but I don't think it's gonna happen.  I'm in eastern NC and ramps seem to be pretty busy when I visit them.
1978 Com-Pac 16
Hull Number 558