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 Post subject: W50 compression
PostPosted: 09 Jul 2019 09:15 
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Skipper

Joined: 24 Sep 2013 09:20
Posts: 365
We're in Fajardo, PR and putting the boat up here for the season. Decided to have a mechanic check out the engine since I've never done that before and am always so nervous about motoring out here in the Caribbean. He ran the engine and saw the small amount of light grey/bluish smoke we've always had at start up and low RPMs as well as small amount of diesel in the water coming out with the exhaust. So, decided to do a compression test. The results are in order of 4,3,2,1: after 5 seconds 525, 495, 420, 420. After 15 seconds 590, 550, 490, 450.

The mechanic says that over 500 is good after 5 seconds. He really seemed to think that 2 and 1 were pretty bad. He knows I don't want a rebuild and would get a new engine so he has no skin in the game. He seemed to recommend that with traveling any distance that I'm pretty close to needing a new engine.

I don't know anything about these compression numbers. Anyone had similar results? What should I do here? If I'm going to need a new engine within the next couple of years, here in Fajardo while we are storing the boat would be a good time to get it done. We are planning to stay in the Caribbean for multiple years. Thoughts?

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Zach Duncan
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 Post subject: Re: W50 compression
PostPosted: 09 Jul 2019 13:28 
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Skipper

Joined: 09 Aug 2017 15:35
Posts: 307
Location: Maine/USVI
Ah, Fajardo. Watch the reef north and south when you leave toward the East. Don't know the compression numbers for my engine, either. Ain't got that far yet. You may "just need rings," but that in itself is a pain.

As to replacement, check in PR for Yanmar, Beta, etc. The ONLY way you can get a Stateside price on Yanmar is stand in front of the dealer in the States, buy the engine, crate it and ship it to PR yourself. Highly protected dealerships, and, as I understand it, the Yanmar/Yamaha dealer for PR is in bed with the Yanmar/Yamaha dealer in the Virgin Islands. Ridiculous prices. I got in trouble with Mac Boring years ago for buying an engine in Maine and it was drop shipped to the V.I. to the DEALER. Who then wanted their markup. I went to pick it up and conflict ensued. I offered to drive my 3/4 ton Silverado through their warehouse doors and they promptly loaded the fully paid for engine into the back of the truck. Snickering something about "no warranty." I took photos of the install, which I did myself, and a dealer Stateside provided full warranty.

Call Parts and Power in Tortola for a better price on Yanmar. One of the Frenchie Fishermen on St. Thomas told me P&P was much cheaper than the St. Thomas dealer.

Or look at Beta. Don't know enough about Beta. Just a Kubota block, parts are cheaper, for sure.

Atmospheric pressure times the compression ratio MIGHT give you the "brand new" compression for the engine, but that would be 30.03 (atm press in Fajardo today) x 21.47 (engine), all divided by 1. That's over 600 psi. But you're asking the wrong guy, and that would undoubtedly vary with RPM.


 
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 Post subject: Re: W50 compression
PostPosted: 10 Jul 2019 07:55 
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Skipper

Joined: 04 Aug 2013 13:33
Posts: 251
I put a new Yanmar in my last boat and the old original engine ran fine when I pulled it but blew oil out the exhaust and into the crank case - it was wore out. (It also had other problems that led to the repowering decision). The point is that although it had to crank too long before firing and starting it ran fine with rings that sounds far worse than yours.

If everything else is in order and the engine has no other issues, it should service your needs until you can repower at what you consider the best time and place. Just my thoughts...

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Dave Lorick
Lunacy #198
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 Post subject: Re: W50 compression
PostPosted: 10 Jul 2019 17:01 
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Able Bodied Seaman

Joined: 16 Jan 2019 08:52
Posts: 49
I guess it really boils down to do you have the twenty grand to put in a new engine. Me, I don't, so I would look at doing a rebuild on the head, probably just rings. Pull it forward with a come along and haul it out through the hatch. Do the work on the hardstand, no biggie. zoombats #337


 
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 Post subject: Re: W50 compression
PostPosted: 11 Jul 2019 06:26 
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Joined: 04 Aug 2013 13:33
Posts: 251
One more thought - if its valves rather than rings, that will need to be fixed. Diesels will run a long time after being 'worn out', but not with burned valves - they get worse. I recall from teen years that the common practice to know if low compression was due to rings or valves was to put oil in the spark plug hole and see if it increased compression. If it did then low compression was from rings, else it was valves and the head should be pulled and inspected. I don't know if this is or is not a good practice with a diesel (pulling an injector to inject a little oil). Did your mechanic that ran the compression test have reason to dismiss valves as a possible cause ?

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Dave Lorick
Lunacy #198
Tampa, FL


 
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 Post subject: Re: W50 compression
PostPosted: 11 Jul 2019 07:21 
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Joined: 24 Sep 2013 09:20
Posts: 365
The mechanic came back the next day, checked the valves, and made adjustments there. He said everything looked good, but they definitely all needed adjusting. After doing that and running the engine again, he seems to think I'm ok for now, meaning that even with the low compression he doesn't think the engine is just going to suddenly die any time soon.

I'm planning to go with it for another season before doing anything major. We'll be either back here in Fajardo or down to Grenada this time next year. I'll plan to check it again at that point and make a decision. I definitely feel that if I ever pull it from it's mounts, it's gone, and a new engine is going in.

As far as the wet test with oil Dave described, the mechanic didn't do that. I did ask on another forum and was told that the wet test would be the next step. Next season I plan to find someone that will do that too. On the other forum, people also seemed to think my current mechanic didn't do the best controlled compression test and left too many variables. For instance, the drop in compression as the tests went along could have been due to the drop in battery voltage as we were further into the test.

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Zach Duncan
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 Post subject: Re: W50 compression
PostPosted: 11 Jul 2019 13:23 
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Joined: 09 Aug 2017 15:35
Posts: 307
Location: Maine/USVI
File away in the back of your mind that when you repower, the shaft angle will undoubtedly change, the engine beds will need work, the shaft will either need to be replaced, or re-cut and re-keyed and the prop may not work with the new installation. But boy is it nice to see a new blue engine sitting there. Or red, I suppose.


 
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 Post subject: Re: W50 compression
PostPosted: 11 Jul 2019 17:21 
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Joined: 29 Dec 2006 09:38
Posts: 544
Compression tests are poor indicators of the health of your engine—unless the cylinders are all really low and the thing won’t start. I don’t like your mechanic already if he thinks a few pounds difference on a test is important. The testing process is difficult to do properly on a diesel because of the high pressures and temps required for the engine to run—and I think is rarely done except to identify a bad cylinder. Compression results vary wildly on how warm the engine is, when it was last run, how much oil gets pumped through during the test and is probably a much better indicator (as someone has mentioned) of valve seating and set than actual overall health of the engine. I would not use compression test to do anything but identify a dead cylinder or faulty valve. Suggesting more implications is absurd. (For you aircraft owners out there, I realize the FAA has some holy grail issues about compression—but it is the same thing with your airplane’s engine). I also would not worry about a bit of blue or white smoke on start up if there is not some kind of significant oil consumption over hours of running. Diesel fuel is actually light oil and burns blue for a bit as it clears out the cylinders on start. White smoke at start up can be condensate blowing out under the pressures created.
If the thing starts and runs, you are obsessing about a bit of smoke on start up. These diesels blocks are just about indestructible and almost impossible to wear out if you keep clean fuel going to them, keep their temperature in range, and provide adequate exhaust freedom. The engine blocks are not where the problems occur. My guess is that most new engines in Tartans (including the one I installed in mine) were not really required, we just got tired of maintaining them. You can ignore maintenance on a new engine for a bit of time and then all of us will be right back where we started with leaks and problems. But I suggest you not look for reasons to replace or overhaul an engine that is running OK. My Westerbeast 50 ran from Panama to Maine with one cylinder with a broken ring. Made a lot of noise and not much compression but got me home.
Ray Durkee
T37 #3734


 
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 Post subject: Re: W50 compression
PostPosted: 11 Jul 2019 18:33 
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Skipper

Joined: 04 Aug 2013 13:33
Posts: 251
Maineiac - I just repowered with a Beta 38. It was a drop-in fit, same shaft / key, angle and regarding color, on recommendation from Mobius I went with the white option and it looks great with the new sound-proofing and repainted white back end.

BTW - the drop-in fit is made possible by the custom mounts option. You fill out a form with about 10 or so measurements and they make the mounts accordingly.

I spent about 3 months altering an engine bed years ago when I put in a Yanmar. Spending a weekend triple checking the dimensions and I think $800 for the option makes custom mounts a great incentive to go Beta.

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Dave Lorick
Lunacy #198
Tampa, FL


 
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 Post subject: Re: W50 compression
PostPosted: 01 Aug 2019 21:29 
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Joined: 14 Jul 2012 20:36
Posts: 380
Ray's post is on money. I replaced a very good running W50. After doing two head jobs and two transmissions in one year, I had lost confidence in the motor and was cruising to further distances. I decided to go with a Beta 35. If you do the head or a rebuild, replace the head studs. They do stretch and are getting harder to find, need to obtain from England.

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