Universal 12 rpm fluctuations

[Dannyboy]

I'm hoping someone out there could shed some insight into a mystery. Here's the scoop.
We have an engine that in neutral, runs smooth from low to high rpm, but in forward, it only runs smooth up to 1000 rpm and then again runs smooth above 2000 and 2600. Everything in between, the rpms surge up and down approximately 100rpm. 
There is significant vibration between 1000 RPM and 2000 RPM.
Some other interesting tidbits:
.
WOT in neutral is 2800 RPM
WOT in forward is 2600 RPM

RPM Verified by mechanic's tach
Injectors and injector pump serviced in September 2014 - no effect on performance
Fuel system tight, filters clean
Prop is 12 RH 9

Boat speed at WOT in calm water is 7 mph.

Thanks!
Dan

[MacGyver]

Going out on a limb here to say cutlass bearing. We had a boat in the harbor doing something very similar, and the mechanic thought it was alignment, etc. went through the usual suspects as the cutlass bearing checked as fine initially.
After replacement as a last ditch effort, it was found to be the culprit, the thought being that at certain engine vibrations, it would sync up with whatever the slight vibration was in the bearing. This caused like a cavitation effect, causing a issue like what you speak of.

Baffled the mechanic, and I as well.

Mac

[deisher6]

Hey Dannyboy:
Very interesting.  Please keep us posted. 

My boat is not much newer than yours....this is why I asked if you had done anything with the shaft log.  I am thinking that it will be first on my list when I next pull the boat.

Thanks for the posting.

regards charlie

[Dannyboy]

So, apparently, the old owner put in a new cutlass bearing and a new prop shaft some time in the last five years. Now, it could be that the installation was botched, based on what I know from the other work he did (or didn't do) recently.

It's not beyond a reasonable doubt. In fact, I've seen some fixes on this boat that Rube Goldberg would be ashamed of, including the water pump being attached to the bulk head with an old dog collar, the wiring being spliced together with trailer hitch hardware, the topside hatches being held on with blue tape, and my favorite, instead of using a new fuel tank, using a yellow 5 gallon can for a tank with the fuel lines just stuck in there, and the tank being held down with straps of duct tape. So, could it be the cutlass bearing? It's as likely as anything else. However, if anyone else has experienced surges and it hasn't been the cutlass bearing, I'd love to know.
Dan

[deisher6]

Hey Dannyboy:
Yep that is definitely the boat that I looked at.  I had forgotten about the fuel tank. 

When you look at the differential in the price of that boat and the market value of a C-27 it is/was a solid deal.  I did not purchase because of the added transportation cost to get the boat to NC.

Still have to admire your determination in tackling the renovation.

Keep up the good work and posts.

regards charlie

[Boat Whisperer]

Hi Folks, Dannyboy's Dad the "Boat Whisperer" here. What I can't figure out is why the engine only goes to 2800 WOT in neutral. I believe it's supposed to be 3600. I was there when the mechanic used his own tach to check the RPM's. Dannyboy is right about past maintenance procedures. Pyxis has a combination of two Universal M12s. Apparently the previous owner buggered up the original and purchased a used replacement. We have enough spare parts to last a long time. The spare injectors, injector pump and starter checked out OK and we have boxes of other good spares. The sail lockers were covered with oil soot from the crankcase breather which was just hanging on the side of the engine. I put in a JEGS 555-52205  air/oil separator and led the vent end to the air intake, so now there's no problem.

The cutlass bearing look brand new with no movement at all. However, I noticed water weeping out under the bearing when we hauled the boat. I plan on removing it to see whats up, but that won't be until May.

Charlie, you are right about the price Dannyboy paid, but the keel repair by Manitowoc Marina was $3400. One big problem was water oozing out of the concrete ballast, even a year after she was on the hard. The previous owner must have sailed the boat for a couple years with the concrete ballast exposed. They drilled holes in the concrete and inserted compressed air pipes. It took about a week to dry out the concrete and then they laid up layer upon layer of glass until you can't tell there was ever any damage.

[Allure2sail]

Hi:
If you search the archives you will find a number of threads about removing the cutlass bearing and its housing removal. Not a nice job but it can be done. Be aware that the bottom bolt and getting it out is the problem.
Best of luck
Bruce
S/V Allure

[redfishnc]

My shaft log was replaced just before I bought my '93 in 2009.  We were getting water in the bilge a few months ago and hauled her out to check.  Bottom bolt was finger tight and I assume it must have been improperly tightened and worked it's way loose.  I am thankful it did not fail completely on our many trips between Oriental and Wrightsville Beach.