Hello everyone! Looking for engine advise. My wife and just looked at a 2000 Mainship 390. We liked the boat but have one major concern. It has a single Yanmar 300hp engine with just about 6000 hours on it. Has all maintenance records and owner is replacing the timing belts this week and transmission oil. How many hours can we realistically get out of this engine if it is indeed in good shape? (will have mechanic look at it) If the engine is "overhauled" how much more life will get get out of it? How much (ballpark) is a replacement?
Need engine advise
- Thread starter KeysGreg
- Start date
The friendliest place on the web for anyone who enjoys boating.
If you have answers, please help by responding to the unanswered posts.
If you have answers, please help by responding to the unanswered posts.
Comodave
Moderator Emeritus
- Joined
- Jul 2, 2015
- Messages
- 21,445
- Location
- Au Gres, MI
- Vessel Name
- Black Dog
- Vessel Make
- Formula 41PC
Welcome aboard. If the engine has been maintained then 10K hours would be reasonable. How much for a new engine, guessing $40K, plus installation. 6,000 hours is higher than normal for that age boat but it also shows that the engine must have been running. What does the overall boat look like? That also should help you figure out how it was maintained.
Mainship Pilot
Senior Member
- Joined
- Oct 18, 2023
- Messages
- 118
- Vessel Name
- Eagle
- Vessel Make
- Mainship Pilot II, Prior vessel 43’ Bluesea
6000 hours sounds like it may have been a charter/commercial boat? Not uncommon at all that kind of service, and if maintained well, 10K is easy, 12-14K as well,however, when you get to those kind of numbers,and love the boat, a repower, may be in your future.
That about 250hrs/year. Not over the top probably at lower than normal RPM. If records show proper maintenance with consistent oil samples, I would be fine with it. Just be aware when you go to sell you will have a very small audience
twistedtree
Guru
Not a big deal itself. Just have the engine checked out and review maintenance records. And look into the “timing belt” replacement. Maybe the Yanmar is different, but I’ve never seen a diesel with a timing belt. Always timing gears. Could be an innocent mistake, or there could be some deep BS at play, so worth investigating.
tiltrider1
Guru
- Joined
- Aug 2, 2017
- Messages
- 4,394
- Location
- Pacific North West
- Vessel Name
- AZZURRA
- Vessel Make
- Ocean Alexander 54
I am not disagreeing with what has already been said. However, we really don't have longevity history on Yanmar engines. It is some what of a guess as to how long they are good for. That said, they may very well be 20,000 hour engines. The closest I can get in comparison is an Isuzu diesel engine that I ran for 28,000 hours in a truck.
Diesel engines wear more by the fuel they consume than by hours. Meaning if this is a plaining hull boat then I would be concerned at 6,000 hours of 80% throttle use. If this is a displacement boat then I am very much less concerned about 6,000 hours at a relaxed pace.
Diesel engines wear more by the fuel they consume than by hours. Meaning if this is a plaining hull boat then I would be concerned at 6,000 hours of 80% throttle use. If this is a displacement boat then I am very much less concerned about 6,000 hours at a relaxed pace.
Jeff F
Guru
- Joined
- Nov 5, 2015
- Messages
- 2,441
- Location
- Canada
- Vessel Name
- Escapade
- Vessel Make
- 50` US Navy Utility trawler conversion
I really doubt that the engine has been flogged on a Mainship 390. Most owners drive them slow.
Incidentally the 390 is the most popular boat for loopers. There are a few of them around now that have done 3 or more loops. That's 1000+ hours per trip.
Incidentally the 390 is the most popular boat for loopers. There are a few of them around now that have done 3 or more loops. That's 1000+ hours per trip.
Duke 239
Veteran Member
- Joined
- Sep 21, 2022
- Messages
- 56
- Vessel Name
- Banna Strand
- Vessel Make
- Seadoo Challenger 230
Yanmars do indeed have timing belts, and 6000 hors. is probably past due if they have never been changed. Timing belts are very rare on marine diesel engines (any diesel engine really) and they do raise some eyebrows.
twistedtree
Guru
Interesting, thanks.
guy with a boat
Guru
It is worth considering that even though rational analysis says the hours are not a problem, there are a lot of future buyers out there that shy away from higher-hours boats. It may still be a great boat for you, but keep in mind when figuring value/purchase price. You may have to discount it some day when you sell, or possibly pay to repower, so adjust purchase price to allow for that.
Pascall
Senior Member
- Joined
- Oct 15, 2022
- Messages
- 284
- Vessel Name
- Passi
- Vessel Make
- Hand made Barkas
Is that the case with all models?
I don't know any better if Yanmar uses gears, can you verify that?
Mvg,
Pascal.
Mambo42
Guru
- Joined
- Oct 26, 2021
- Messages
- 713
- Vessel Name
- Endless Summer
- Vessel Make
- 1979 Defever 49
In addition to what others have said I would probably do a compression test and a boroscope of the cylinders. This will give you a good indication of the state of the engine. If that compression test is OK, you can proceed with the rest of the work.
If the cylinders and pistons have a lot of carbon deposit you may want to think about taking the cylinder head off in order to clean the pistons and cylinders. It is a nasty, dirty job, but with brake cleaner you can get them perfect again. In the mean time I would clean the cylinder head, get new valve seats (new valves if necessary) and clean the injectors.
Then change all the coolers and the raw water impeller. Perhaps even overhaul the raw water pump, change all the anodes and then the engine should be reliable again for many hours.
I know this is a lot of work, will also cost some money, but at least then you know what you have.
If the cylinders and pistons have a lot of carbon deposit you may want to think about taking the cylinder head off in order to clean the pistons and cylinders. It is a nasty, dirty job, but with brake cleaner you can get them perfect again. In the mean time I would clean the cylinder head, get new valve seats (new valves if necessary) and clean the injectors.
Then change all the coolers and the raw water impeller. Perhaps even overhaul the raw water pump, change all the anodes and then the engine should be reliable again for many hours.
I know this is a lot of work, will also cost some money, but at least then you know what you have.
Thanks everyone
Thanks you everyone for the information. The boat has done the loop 3.5 times. I think we are putting this one on the back of the list right now. I'm just a bit nervous about it and because of that I will be nervous all the time. Also as a friend suggested if and when we decide to sell it the potential buyers will have the same questions/ nervousness that we are having.
Thanks you everyone for the information. The boat has done the loop 3.5 times. I think we are putting this one on the back of the list right now. I'm just a bit nervous about it and because of that I will be nervous all the time. Also as a friend suggested if and when we decide to sell it the potential buyers will have the same questions/ nervousness that we are having.
The Yanmar 4L and 6L were designed specifically for marine use....and are the 'real McCoy'.
Check your engine's suffix letters for exact model, then take a look at the bottom link.
I recall when they first came out in early 2000ish. The 4LH (4cyl) was designed as a replacement for American big block v-8 gas marine engines....they do, and do it well. ( and I'm a 'dyed in the wool' USA guy lol!)
https://www.yanmar.com/media/global...ion/operationmanual/6LPA_OPM_0A6LP-G00103.pdf
Check your engine's suffix letters for exact model, then take a look at the bottom link.
I recall when they first came out in early 2000ish. The 4LH (4cyl) was designed as a replacement for American big block v-8 gas marine engines....they do, and do it well. ( and I'm a 'dyed in the wool' USA guy lol!)
https://www.yanmar.com/media/global...ion/operationmanual/6LPA_OPM_0A6LP-G00103.pdf
I believe we have been talking about the Yanmar 6LP model since it is the only one of that era with a toothed belt driving the camshaft.
It is a solid engine that uses the block developed by Toyota for their Land Cruiser. Yanmar specifies changing the belt every 1250 hours after breakin.
So the belt was probably changed several times in the past. But if the belt hasn’t snapped yet, scrambling the valves, once it is replaced it is good to go for the next interval.
I know that statement will scare some but I suspect Yanmar’s change interval is very, very conservative and I have never heard of the belt failing on a Yanmar.
A blow by test, either the shade tree mechanic procedure of holding your hand over the crankcase vent or the more elaborate quantitative test procedure, will give you a pretty good indication of expected future life.
David
It is a solid engine that uses the block developed by Toyota for their Land Cruiser. Yanmar specifies changing the belt every 1250 hours after breakin.
So the belt was probably changed several times in the past. But if the belt hasn’t snapped yet, scrambling the valves, once it is replaced it is good to go for the next interval.
I know that statement will scare some but I suspect Yanmar’s change interval is very, very conservative and I have never heard of the belt failing on a Yanmar.
A blow by test, either the shade tree mechanic procedure of holding your hand over the crankcase vent or the more elaborate quantitative test procedure, will give you a pretty good indication of expected future life.
David
SteveK
Guru
- Joined
- Jul 5, 2019
- Messages
- 5,211
- Location
- Gulf Isalnds BC canada
- Vessel Name
- Sea Sanctuary
- Vessel Make
- Bayliner 4588
Good question and answers.
A mechanical survey is about to be done. Have you asked these questions of that surveyor?
A mechanical survey is about to be done. Have you asked these questions of that surveyor?
Gotcha on comfort level....
I do recall reading of one 6L warranty instance concerning a valve stem seal. Repaired and warranty was extended by factory to 5,000 hr.
Also, google 'is Yanmar 6L a good engine'. See what comes up from users on sites like The Hull Truth, and Offshore Only etc.
rgano
Guru
- Joined
- Oct 8, 2007
- Messages
- 5,015
- Location
- USA
- Vessel Name
- FROLIC
- Vessel Make
- Mainship 30 Pilot II since 2015. GB-42 1986-2015. Former Unlimited Tonnage Master
I quite agree, and when I bought this Mainship with a 15-year old Yanmar 6LP but with only 450 hours, I changed the timing belt out of an abundance of caution. I also had the intercooler serviced as that is another place that bad things can happen to ruin and engine very quickly.
Duke 239
Veteran Member
- Joined
- Sep 21, 2022
- Messages
- 56
- Vessel Name
- Banna Strand
- Vessel Make
- Seadoo Challenger 230
Cool pics in this thread:
https://www.thehulltruth.com/boating-forum/1161179-yanmar-6lp-timing-belt.html
https://www.thehulltruth.com/boating-forum/1161179-yanmar-6lp-timing-belt.html
Waterant
Senior Member
Something to consider: A full rebuild of this engine will cost ~$24k and will reset the engine hours.
It will be much less expensive than an engine replacement, especially if you will have to go with a different engine because of availability.
It will be much less expensive than an engine replacement, especially if you will have to go with a different engine because of availability.
In general all of the older mechanically injected engines like the Yanmar 6LP have been discontinued and replaced with high performance, common rail injected engines.
If your 6LP or similar needs to be rebuilt or replaced it will be a tough decision. There aren’t too many people I would trust to rebuild the 6LP. OTOH a brand new common rail engine will be expensive and installation won’t be cheap, due to different mounts, exhaust configuration, output shaft placement, etc.
But this thread has drifted far off track. The OP was considering a 6,000 hour Yanmar and asked if they held up well for that long or longer.
David
If your 6LP or similar needs to be rebuilt or replaced it will be a tough decision. There aren’t too many people I would trust to rebuild the 6LP. OTOH a brand new common rail engine will be expensive and installation won’t be cheap, due to different mounts, exhaust configuration, output shaft placement, etc.
But this thread has drifted far off track. The OP was considering a 6,000 hour Yanmar and asked if they held up well for that long or longer.
David
