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Yanmar 3QM30F vs Perkins 4-108

Jon Westdal

Jon Westdal

New Member
Hello all,

First time poster here. My wife and I are looking to purchase a sailboat. Having sailed in a Morgan 34 from Fort Lauderdale to the BVI's, a life time ago, I have always had a soft spot for Morgans. We're looking, well were going to be looking when get done done wandering around Alaska, for a 382/83/84. I see that some have the 30hp Yanmar and some have the 48?hp Perkins. Does the Yanmar have the power for fight a strong current? I have to admit that having grown up rebuilding British iron I am more at home with the Perkins but what do those in the know think?
 
Jon

The first 100 or so Morgan 382's came with the Yanmar 3QM30. The next almost 500 382's,383's & 384's came with the Perkins. The Yanmar is rated at 30hp while the Perkins is rated at 50hp. The difference is in how the engines horsepower is measured. I'm told that the Yanmar is measured after the transmission and the Perkins is measured before the transmission. So in actuality both engines deliver about the same power.

My 382, hull #53, has the Yanmar. We have over 6000 hours on it and it has never left us wanting for power. We do detailed maintaince on the engine and she pushes the hull at 6.2 kts in calm water. The problem with the Yanmar is that the original parts are getting harder to find. I think the same would be said for the Perkins. Many of the boats still sailing have had their engines replaced. It is not easy to justify spending the money required to repower on an older boat. My feelings are that the older, heavier, slower rpm engines (called rock crushers), are more dependable and longer lasting then the newer engines.

One thing I would recommend, regardless of which engine the boat your looking at has, Make sure that it is a fresh water cooled model. Any engine that is salt water cooled has a much shorter lifespan.

Hopes this helps. Good luck in your search. You won't go wrong with one of these boats for the money.

Jim
 
J
jimcleary said:
Jon

The first 100 or so Morgan 382's came with the Yanmar 3QM30. The next almost 500 382's,383's & 384's came with the Perkins. The Yanmar is rated at 30hp while the Perkins is rated at 50hp. The difference is in how the engines horsepower is measured. I'm told that the Yanmar is measured after the transmission and the Perkins is measured before the transmission. So in actuality both engines deliver about the same power.

My 382, hull #53, has the Yanmar. We have over 6000 hours on it and it has never left us wanting for power. We do detailed maintaince on the engine and she pushes the hull at 6.2 kts in calm water. The problem with the Yanmar is that the original parts are getting harder to find. I think the same would be said for the Perkins. Many of the boats still sailing have had their engines replaced. It is not easy to justify spending the money required to repower on an older boat. My feelings are that the older, heavier, slower rpm engines (called rock crushers), are more dependable and longer lasting then the newer engines.

One thing I would recommend, regardless of which engine the boat your looking at has, Make sure that it is a fresh water cooled model. Any engine that is salt water cooled has a much shorter lifespan.

Hopes this helps. Good luck in your search. You won't go wrong with one of these boats for the money.

Jim
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Jim, Thanks for clearing that up. All my experience is with truck engines. I know what you mean about a rock crusher. An old 855 Cummings stupid diesel will just about run forever.
 
There are several sources for 4-108 parts. That is not yet an issue in my experience. They seem to be reliable, but leak oil. That can be mitigated but not eliminated.
 
I will chime in here as I have had a wide range of engine experience over the past 2 years with my beloved Perkins 4-108. I have had leaks the entire time I have had the boat (5 3/4 years now) and when my IP went out about 2 years ago, i went ahead and had the mechanic jack up the engine and replace rear seal and front seal. The significant leaks pretty much all emanate from those 2 places. The repair to stop the rear seal leak did not work. It leaks less, but it leaks. The front leaks far less now.... but still leaks. I just put the absorbent pads underneath and just replace them, not a huge deal. So the only major repair I have had to do on the engine is the IP rebuild. As you know, with almost all of the older diesels, it's a function of keeping oil and filters changed, keeping fuel filters changed regularly and clean fuel in the injectors... My Perkins has 5,396 hours on it now and when I bought it, it had 4,900+/- on it.... It's pretty easy to do the oil and fuel filter changes, the bleeding of the injectors is pretty easy.... It has no glow plugs and on any Florida winter day (I know it is not comparable in any way to up North), it starts first time nearly every time... so I'm a fan... parts are still available, including cylinder liners and other parts for top and bottom rebuild kits... I'm sticking with it! I need to replace my fuel tank filler hose and I need to remove the tank cover and drain and swab out the tank to keep clean fresh fuel going to the pump and injectors... I'd say that's the biggest thing to longevity other than regular oil and filter changes. I usually never run mine over about 2300 RPMs as well....
 

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oh yea, and while it goes without saying, keeping the impeller fresh and the coolant and water flow over the heat exchanger is crucial as well...
 
Terry and John thanks for the info, all good to know. I like the simplicity of the older engines. No turbo, no computer control to goof up. I had a turbo blow in a detroit on the 90, near Rochester Minnesota. What a mess. Large amounts of high pressure oil squirted everywhere. Having that happen in your boats engine compartment, oh my.
 
I have had no issue getting parts for my Perkins 4-108 as well. I am currently finishing an overhaul I am doing most on my own. The rebuild kit at under 600.00 US included all seals and gaskets, all valves and valve springs and guides, new pistons and rings, all new rod and main bearings, new front and rear main seals and new cylinder liners. The HP is a bit oversize in my opinion on the Perkins, I push through the water at about 6.5 kts at no more than 2300 RPM. Anything more and the prop starts cavitating and I have a large fixed three blade. Normal cursing is 2000 RPM and 6 kts. Solid engine if you don't mind the leaks.
 
All, interesting as to the rpm we Perkins owners turn. Must have to do with ratios & transmission replacements. My useable rpm range was 15-3000 rpm. The engine would rev higher (4-108 was rated 50hp @ 4000 rpm) but at little increase of speed. I had the stock 3 blade & Hurth 150 transmission. Topped out at 7.2K, liked to cruise around 6-6.5K.

Jon, the boat would plow through anything including including some docks (I think!?) Its good to have an excess of power. You just increase rpm by 500 to maintain your desired cruising speed in wind or waves. The Perkins will do that. Many, many years ago Practical Sailor surveyed marine mechanics as to their "favorite" engine. The conclusion was the Perkins 4-108. Admittedly that was before Yanmar took over the entire sailboat market.

Replace all the coolant hoses, also the oil heat exchanger oil delivery lines, rebuild the injectors, adjust the valves, feed it very clean fuel and change the oil end of season. They'll last a loooong time.
 
Sounds like good advice Dave. I'm getting off my original topic here. I read you should re-torque the head bolts as part of ongoing maintenance. I'm thinking if the PO's didn't re-torque the bolts, starting now could lead to a snapped head bolt. But if you don't perhaps a blown head gasket.
 
I wouldn't think a diesel head bolt would snap on retorque unless it spent its life in coolant. I don't know off the top of my head if the Perkins bolts do. I don't think so.
Get a Perkins 4-108 shop manual before you do any of that. One other concern with all old diesels is that modern fuel is low sulphur. Sulphur lubricated parts such as the high pressure pump. So an additive might be called for if you believe that is a concern. I used a fuel conditioner and a biocide after having the injectors rebuilt and fuel tank cleaned. Never dirtied a Racor filter or had the vacuum gauge rise for what its worth. Cleaning an old tank is very important in my opinion.

There are a lot of 4-108's in bobcats & wood chippers. So the aftermarket availability will continue for a while. My local diesel injector shop had no concerns rebuilding pumps or injectors. My 2 cents.
 
dave_a said:
I wouldn't think a diesel head bolt would snap on retorque unless it spent its life in coolant. I don't know off the top of my head if the Perkins bolts do. I don't think so.
Get a Perkins 4-108 shop manual before you do any of that. One other concern with all old diesels is that modern fuel is low sulphur. Sulphur lubricated parts such as the high pressure pump. So an additive might be called for if you believe that is a concern. I used a fuel conditioner and a biocide after having the injectors rebuilt and fuel tank cleaned. Never dirtied a Racor filter or had the vacuum gauge rise for what its worth. Cleaning an old tank is very important in my opinion.

There are a lot of 4-108's in bobcats & wood chippers. So the aftermarket availability will continue for a while. My local diesel injector shop had no concerns rebuilding pumps or injectors. My 2 cents.
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Wished I had the availability of a good mechanic where I’m at. No luck
 
jimcleary said:
Jon

The first 100 or so Morgan 382's came with the Yanmar 3QM30. The next almost 500 382's,383's & 384's came with the Perkins. The Yanmar is rated at 30hp while the Perkins is rated at 50hp. The difference is in how the engines horsepower is measured. I'm told that the Yanmar is measured after the transmission and the Perkins is measured before the transmission. So in actuality both engines deliver about the same power.

My 382, hull #53, has the Yanmar. We have over 6000 hours on it and it has never left us wanting for power. We do detailed maintaince on the engine and she pushes the hull at 6.2 kts in calm water. The problem with the Yanmar is that the original parts are getting harder to find. I think the same would be said for the Perkins. Many of the boats still sailing have had their engines replaced. It is not easy to justify spending the money required to repower on an older boat. My feelings are that the older, heavier, slower rpm engines (called rock crushers), are more dependable and longer lasting then the newer engines.

One thing I would recommend, regardless of which engine the boat your looking at has, Make sure that it is a fresh water cooled model. Any engine that is salt water cooled has a much shorter lifespan.

Hopes this helps. Good luck in your search. You won't go wrong with one of these boats for the money.

Jim
Click to expand...
Hi Jim,
We are hauled out up the CT River and I have pulled out the Perkins 4-108. I am in the process having it checked out and replacing the leaking oil seals, particularly the rear crankshaft seal. I'm also contemplating a repower. Do you know if any of the new engines are available with the same footprint and shaft coupling position and angle. I just installed a new prop shaft and would like to avoid having to replace it again, given that it requires dropping the rudder, a significant chore.
Best,
John
 
I just installed a Beta35. I had to cut the shaft only because I installed a new MaxProp, and because of a 1" error by the yard in engine placement. Mark Pearson installed a common rail Yanmar 45 recently. Don't know if he had to change the shaft. You would not have to replace the shaft in any case. Maybe cut it.
 
That is good news Terry. On my 384 I have to drop the rudder to pull the shaft because of the straight rudderpost. So I would have to do this if I need to shorten the shaft and have the coupler re-trued onto the shaft.
 
Well don't take my word completely. Carefully measure too, of course. If you are installing a new engine, you could pull the shaft out from inside, I believe, assuming you can pull your prop. The rudder has to come down to install or remove a MaxProp, however.
 
That's a good point about removing the shaft from the inside. From Beta's website they say that they will match for the shaft also so it truly will be a drop in installation. I have inquired with them about this and using my relatively new gearbox. This make repowering much more attractive to me.
No more leaking oil, soot staining the transom, difficulty with having to bleed at the injectors when changing the fuel filter, reaching to the back of the engine for the oil dipstick, etc. Lot's of positives including the digital monitoring of the engine on the MFD or phone!
 
From what I have heard, I would stay away from the standard Beta TMC transmission . I put on a ZF12M There is a Beta Marine Owners Group on Facebook. You can learn a lot there, but beware of taking it all at face value. People who post often do so only when they have problems and those without problems may not join. I went to Beta because, unlike Mark Pearson, I did feel comfortable with a computer driven engine. In return, of course, I don't have the quiet fuel efficiency he got with a new Yanmar.
 
I am very comfortable with electronics and fuel injection, and have done a few custom efi installs. But my last two outings in my 382 with the 4-108 have been with zero working alternator and engine instruments, including a non working key start. There is some real comfort in a diesel that requires no electrics to run, just short across the main starter and solenoid terminals and it fires right up.
 
moltzvt said:
I have had no issue getting parts for my Perkins 4-108 as well. I am currently finishing an overhaul I am doing most on my own. The rebuild kit at under 600.00 US included all seals and gaskets, all valves and valve springs and guides, new pistons and rings, all new rod and main bearings, new front and rear main seals and new cylinder liners. The HP is a bit oversize in my opinion on the Perkins, I push through the water at about 6.5 kts at no more than 2300 RPM. Anything more and the prop starts cavitating and I have a large fixed three blade. Normal cursing is 2000 RPM and 6 kts. Solid engine if you don't mind the leaks.
Click to expand...
I'm currently needing parts for my Perkins. Where could I find a rebuilt kit? Sure would appreciate any info.
 
moltzvt said:
I have had no issue getting parts for my Perkins 4-108 as well. I am currently finishing an overhaul I am doing most on my own. The rebuild kit at under 600.00 US included all seals and gaskets, all valves and valve springs and guides, new pistons and rings, all new rod and main bearings, new front and rear main seals and new cylinder liners. The HP is a bit oversize in my opinion on the Perkins, I push through the water at about 6.5 kts at no more than 2300 RPM. Anything more and the prop starts cavitating and I have a large fixed three blade. Normal cursing is 2000 RPM and 6 kts. Solid engine if you don't mind the leaks.
Click to expand...
I’m looking at a 383 that is probably going to need a rebuild so instead of starting another thread let me ask you this… I have been able to find print manuals online but videos concerning rebuilding a 4-108 seem to be hard to come by. The few YT vids are either incomplete or so poorly filmed that they’re useless. Do you know of a 4-108 how-to rebuild video?
 
I'll chime in here and suggest that if you can follow and understand the service manual, and you have either a micrometer set and snap gauges, or know how to use Plastiguage, you can rebuild it yourself. I would NOT trust a YouTube video for this. The Perkins is a VERY basic engine. However, if you have specific damage leading you to need to rebuild, and little experience, then it could be more difficult, but still ok to do for the novice. I would suggest taking the entire head assembly to an automotive machine shop and let them deal with that, having special valve grinding equipment.
 
Yeah, the head work is definitely going to the pros, but if I’m having trouble visualizing something in a manual, having a video to reference to bolster what the manual is saying helps me tremendously.
 
Consider $ and time here. I am not sure one should rebuild a 40 year old engine. I am told by experts they often don't last long. Also, parts for the won derful old 4-108 are getting harder to find. I purchased a Beta 35, smaller, but plenty for our boats. Got a ZF transmission, not the one that is standard. If you are handy enough to rebuild a Perkins, you could install it yourself. And Beta will make special mounting brackets to fit your boat. (My dealer, who is less than helpful, did not tell me that, so my yard had to fabricate the brackets. On the other hand, I made sure they are strong enough so that if we ever are knocked down or capsized, the engine will stay in place.)
 
I think one of the really nice points about a Perkins rebuild is that this is a removable cylinder liner design, you just press the liners out and press the new ones in. And it looks like they aren't a really tight fit liner, size in size I believe, so not difficult to do. This makes for unlimited rebuilds, there is no "last oversize" on the block, and you don't need to take the block to an engine shop, probably only the head.
I wouldn't mind if my 4-108 needed a rebuild, it looks like crap now, it would give me a chance to repaint it and make it all shiny new. But, alas, it runs so well, and burns very little oil for a 44 year old and just does not need it.
 
terry_thatcher said:
Consider $ and time here. I am not sure one should rebuild a 40 year old engine. I am told by experts they often don't last long. Also, parts for the won derful old 4-108 are getting harder to find. I purchased a Beta 35, smaller, but plenty for our boats. Got a ZF transmission, not the one that is standard. If you are handy enough to rebuild a Perkins, you could install it yourself. And Beta will make special mounting brackets to fit your boat. (My dealer, who is less than helpful, did not tell me that, so my yard had to fabricate the brackets. On the other hand, I made sure they are strong enough so that if we ever are knocked down or capsized, the engine will stay in place.)
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That surprising, I’ve always heard Beta had pretty good customer service. If I do reposed instead of rebuild, it’ll be a Beta for sure.
 
It was just my local dealer. The folks in North Carolina are easy to work with and the folks in the UK are very responsive. The main distributor in California has folks that always seem put out to be asked questions. I now get parts from Carolina and ask technical questions of the UK.
 
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