To rebuild engine or not... that is the question

[sailingunity]

Over the last few weeks I've been making preparations to remove my engine and rebuild it, but I'm having second thoughts.

It's the original engine to my 1974 boat, a Westerbeke W-80. The previous owner rebuild the transmission in 2013. He almost rebuilt the engine in 2008 but mechanic said it was fine. The boat has since completed a circumnavigation. Engine has 6000+ hrs on it (tach has been replaced several times so it's hard to say)

About 4 years ago I discovered a puddle of coolant in the intake manifold. The manifold is not water cooled. I removed the head and had it looked over, no cracks. The exhaust manifold / coolant tank, on the other hand, had a some corrosion that could have cause a leak, coolant could have gotten into one of the cylinders and then back up into the intake (this is speculation, as it would have needed fill up the exhaust hose before flooding the engine - requiring gallons of coolant). I also found and replaced 1 bent pushrod during this top end rebuild.

Due to a torqueing mistake, we lost the valves to cylinder 1 while cruising and it ran for about an hour like this (idling of course) while we got to a safe anchorage. We fixed it and continued on for months with no issues so far. It still starts right up, however I was concerned the rings might have been damaged on this cylinder.

I performed a compression test on all cylinders and found them to be at or above spec, with cylinders #1 (where the valves stopped opening) and #4 (where the suspected coolant was) being at spec of 16.5:1 and #2 and #3 being above spec by about 15%. The variance is outside of the typical acceptable tolerance of 10%. Unsure what the reason for this is, but we do get a lot of vibration at idle and I wonder if that is what is causing this.

One of the engine mounts is pretty rusted from a leaking mixing elbow (replaced now). The paint on the engine needs refreshing. There is also a leaking drain tap on the block that has been "fixed" with some steel stick - I think the hole needs to be re-tapped which is difficult to do in-situ because of the transmission housing.

All of this led me to the decision to pull the engine and do a rebuild on it, which I have wonderful access to through the cockpit floor, but all of that being said, it still starts and runs just fine. Am I overkilling this thing? Should I just slap some new paint on it, replace the one engine mount and call it a day?

[Lepke]

If the compress is at or above spec and decent oil pressure, you probably have an engine that will be reliable for several years with the usual maintenance.
Rebuilding an engine with good compression makes no sense at all.

[paralog]

Originally Posted by sailingunity

Over the last few weeks I've been making preparations to remove my engine and rebuild it, but I'm having second thoughts.

It's the original engine to my 1974 boat, a Westerbeke W-80. The previous owner rebuild the transmission in 2013. He almost rebuilt the engine in 2008 but mechanic said it was fine. The boat has since completed a circumnavigation. Engine has 6000+ hrs on it (tach has been replaced several times so it's hard to say)

About 4 years ago I discovered a puddle of coolant in the intake manifold. The manifold is not water cooled. I removed the head and had it looked over, no cracks. The exhaust manifold / coolant tank, on the other hand, had a some corrosion that could have cause a leak, coolant could have gotten into one of the cylinders and then back up into the intake (this is speculation, as it would have needed fill up the exhaust hose before flooding the engine - requiring gallons of coolant). I also found and replaced 1 bent pushrod during this top end rebuild.

Due to a torqueing mistake, we lost the valves to cylinder 1 while cruising and it ran for about an hour like this (idling of course) while we got to a safe anchorage. We fixed it and continued on for months with no issues so far. It still starts right up, however I was concerned the rings might have been damaged on this cylinder.

I performed a compression test on all cylinders and found them to be at or above spec, with cylinders #1 (where the valves stopped opening) and #4 (where the suspected coolant was) being at spec of 16.5:1 and #2 and #3 being above spec by about 15%. The variance is outside of the typical acceptable tolerance of 10%. Unsure what the reason for this is, but we do get a lot of vibration at idle and I wonder if that is what is causing this.

One of the engine mounts is pretty rusted from a leaking mixing elbow (replaced now). The paint on the engine needs refreshing. There is also a leaking drain tap on the block that has been "fixed" with some steel stick - I think the hole needs to be re-tapped which is difficult to do in-situ because of the transmission housing.

All of this led me to the decision to pull the engine and do a rebuild on it, which I have wonderful access to through the cockpit floor, but all of that being said, it still starts and runs just fine. Am I overkilling this thing? Should I just slap some new paint on it, replace the one engine mount and call it a day?

With this amount of hours and age, I would purchase a new engine if you are planning on going any real distance from home. Otherwise a touch up and replacement of mounts should be ok.

[stormalong]

Engine mounts need to be replaced every 5-10 years anyway. If yours are older than that replace them all.

The leaking drain tap can be drilled and tapped to the next larger pipe size and a reducer used. Maybe a helicoil kit would work. I know you said that the access is difficult but there must be a way.

Have you checked the injectors. At 6,000 hours they are past due for testing and servicing or replacing. If the engine is rough at idle a simple test is to loosen the high pressure pipe fitting on each injector, one at a time and see how it affects the roughness. If you come to one where the engine does not change in tempo when loosened that injector needs work. The other thing to do is to remove them, marking which cylinder each came from, take it to a diesel shop and get them tested. They will have a machine to pump fuel through the nozzle so they can observe the spray pattern.

An engine that has been well maintained throughout it's life has a long way to go beyond 6,000 hours. Even if it is 50 years old. Do the small repairs and you could go for many more years of service.

[RaymondR]

6,000/24/365 = 0.684 years.

Diesel engines on gensets run for many years before being overhauled or replaced.

Waste of money to throw away an engine that is basically just run in and which you know intimately and love.

[David Mathis]

The three cylinder Yanmar generator engine in our powerboat has about a bazillion hours (Hobbs stopped working many years ago so total hours unknown). It gradually seemed to be working harder when both air conditioners were running then the water heater came on so a mechanic was hired to check the valve clearance. He reported the valves were far too tight indicating they had worn into the head. The head was removed and his diagnosis was found to be correct. New valves, guides, seals, springs, and injectors along with new seats resulted in a much better running engine. The exhaust ports had thick carbon deposits so the head was soaked for a thorough cleaning. It's interesting that the compression was excellent and no cylinder wear was detected not was even the slightest cylinder ridge apparent. That was a few years ago and it still runs like new.

Based on this experience, having the head reconditioned may resolve most of the problems.