Advice - Westerbeke 30b Spun Bearing

[jsut210]

Sadly this weekend my engine, a Westerbeke 30b, developed a rod knock as I was returning to my slip under power. Upon hearing the noise I noted no abnormal engine conditions, but immediately shut everything down and sailed the rest of the way home. I've been paying close attention to the engine temps and oil pressures since de-winterizing and haven't noticed anything out of the normal this season (~170 deg water temp and no less than 30 psi of oil pressure at idle when hot. Closer to 50psi at idle when cold). I drained the oil which was slighty metallic and the dropped the pan to find obvious signs of bearing failure. I felt the play in all three rod ends and cylinder one was the culprit. I pulled the rod end off to reveal:

I went ahead and took the other end caps off; they looked and felt fine but I will follow up with a proper measurement to see if they're in spec. This is such a bummer way to kick off the sailing season. If anyone would be willing to share some wisdom I have a few questions:

How screwed am I? I honestly can't tell if the crank is salvageable. The crank journal is trashed and the discoloration scares me. The discoloration is not isolated to the bad cylinder which makes me raise an eyebrow though. Right now my fingers are crossed that if I take the crank to a machine shop they can turn/polish the journal within spec of one of the two available undersized bearings. A new crankshaft is going to run over $2k. I'd have to believe that rod #1 is trashed as well? There goes another $500.

What might have caused this? I always thought a spun bearing was a result of a loss in oil pressure. The only maintenance I've done this year post de-winterization is the standard oil / filter + fuel filter change. I'm really worried that even if I repair the crank, bearing, and rod, I'll just spin another bearing.

What course of action would you recommend in general? This boat with a running engine is probably not worth more than $10k.

Can anyone recommend a machine shop, or even a mobile mechanic in the greater Chesapeake (Baltimore specifically) area that might be willing to take aspects of this repair on?

Thanks everyone.

 

[Ted]

What might have caused this? I always thought a spun bearing was a result of a loss in oil pressure. The only maintenance I've done this year post de-winterization is the standard oil / filter + fuel filter change. I'm really worried that even if I repair the crank, bearing, and rod, I'll just spin another bearing.

This could have been caused by the bearing clearances being too tight for the oil viscosity being used. Engines with tight rod bearing clearances usually require a thin multi-viscosity motor oil. If you fill the crankcase with a thicker oil and you could have problems. Tighter bearing clearances require thinner oils while looser bearing clearances need thicker oil to maintain the protective oil film between the bearings and their journals.

Also, cold starts, especially in close tolerance engines running thicker oils could contribute to this problem.

 

[shemandr]

Not knowing what a spun bearing is I googled the term. Here is what came up first:

Spun Bearings - Engines

Spun rod bearings are the most common failure. A spun rod bearing will tear up the big end bore in the rod.

www.enginebuildermag.com

I don't understand much of it but it does buttress @Ted's post above. All in 32 minutes (Between the OP and Ted's answer.) Good on yer Ted!
Sorry about @ jsut207 's engine.

 

[kloudie1]

The engine is probably manufactured by Kubota with Westerbeke marine stuff bolted on. The engine block number should be somewhere on the block casting and that can be used to figure which Kubota it is. Then parts can be sourced from Kubota (usually a lot less expensive) instead of Westerbeke. Measurements on the crank will tell ya if it can be saved by grinding.. The rod is most likely toast but measurement is the only way to tell.
Have you pulled the main bearing caps ? The crankshaft looks to have heat discoloration under the #1 and #2 main bearing caps.. (maybe a smidge on #3 as well)
That is probably not the original engine? Most Ranger 30's had an Atomic 4 gasoline engine..
Good luck with it ..

 

[jsut210]

The engine is probably manufactured by Kubota with Westerbeke marine stuff bolted on. The engine block number should be somewhere on the block casting and that can be used to figure which Kubota it is. Then parts can be sourced from Kubota (usually a lot less expensive) instead of Westerbeke. Measurements on the crank will tell ya if it can be saved by grinding.. The rod is most likely toast but measurement is the only way to tell.
Have you pulled the main bearing caps ? The crankshaft looks to have heat discoloration under the #1 and #2 main bearing caps.. (maybe a smidge on #3 as well)
That is probably not the original engine? Most Ranger 30's had an Atomic 4 gasoline engine..
Good luck with it ..

Good call with the alternate manufacturer - the 30b three appears to be a Mitsubishi L3E. Some parts available at 1/4 to 1/10th the price. The service manuals are shockingly similar with identical tolerances. After a quick search I'm not seeing a lot of replacement crankshafts in North America. I'm skeptical about these Aliexpress cranks.

I haven't looked at any main bearings yet but I see what you're talking about. I'll pop those off as soon as I drag the engine forward so I can work on it.

You're right, the previous owner re-powered an unknown number of hours/years ago. When I took ownership, the alternator had a broken wire which for whatever reason caused the hour meter to not run... yikes

 

[kloudie1]

Good to know that it is a Mitsu.. I'd worked a bit on a 4 cyl Westerbeke that is a Mitsu, but I didn't know that the three cyl Westies might be Mitsu as well.