Repowering: Perkins 4-108 to Yanmar 4JH45

Our Perkins totally shat the proverbial bed and sprayed oil everywhere on a Labor Day cruise. It was a $1k tow job to get her home, but Thank God for Boat US towing insurance! Didn't cost anything.

Unlike most folks on this forum who love their Perkins, we have had nothing but bad luck. We've pumped a lot of money into the old Perkins and he wasn't returning the love. His default behavior was spraying oil everywhere despite expensive head gasket replacements and other work. Thick clouds of smoke on startup.

So after much thinking, discussing, researching we decided we were going to repower. After all, 35+ years isn't really too bad for an engine. We are going to continue to do some long distance cruising & need reliability.

We also spent a lot of time considering which engine to replace him with. We talked with people who know much more about marine engines than we do. We narrowed it down to Yanmar 4JH45 (45 HP), Volvo D2-40 (40 HP), or Beta Marine 38 (38 HP). I think any of these 3 would have worked fine, and the Volvo & Beta have worked fine for other forum members. Also if our Perkins was not possessed by the devil, keeping it would have been much preferable.

After much reading & discussion we decided to try the Yanmar. This made us a little nervous because (that we know) nobody else on this forum has tried this Yanmar model in an M38. It's the newer high tech 'common rail' that develops up to 30,000 psi, which makes many people apprehensive. We have never shied away from embracing newer technology and we've only been burned a couple of times. Our thinking is that Yanmar is offering a 5 year warranty so if there is a flaw, they have some skin in the game too.

Flash forward 6 weeks and we've got the new engine installed and so far we love it. Granted we've only taken it out twice for sea trials. But it starts in 1 second, and doesn't blow smoke or oil everywhere. It is easily less than 1/2 the noise and near zero vibration. Compared to our Perkins which always had an apocalyptic Mad Max feeling when it started.

Here are some after/before pictures. You can guess which is 'before' and which is 'after'. Note the easy accessibility to everything. The primary and secondary fuel filters are in the upper left section. No more trying to crawl under the galley sink to replace a filter while bashing around in the sea.



Below shows the transmission and newer dripless which we replaced a couple of years ago.



While we were doing all this engine compartment work, we also totally re-did the exhaust system. Muffler, riser, pipes, etc. The old riser was quite low and the engine company said we could get water entering the engine. Which we have had.

The engine fit quite well on the stringers used for the Perkins. They just put down some angle iron on top, and some pads made of Star Board.

The engine is 45HP, and we got the KM35P transmission which has a ratio of 2.36

This spring when we haul her for a bottom painting we plan to replace the fixed 3 blade propeller with a new feathering prop. With the old prop we have a top speed of around 6.3kt and with the new (properly sized) prop I'm expecting that to be closer to 7kt.

For those too polite to ask: the engine cost about 12 Boat Bucks*, but with all the new exhaust, plumbing, etc. the total was more around 20 Boat Bucks. Our rationale is that we are going to be doing this very active boating for at least another 10 years. And if you spread that over 10 years, it's not so bad, right???!!

I'll keep posting on here if we have any problems/issues with the new rig.

Cheers!
-Mark

* Boat Buck is a happily mysterious currency of unknown value. There are rumors that 1 Boat Buck is worth approximately 1k US dollars.

Geez, that old Perk was quite the oil spill, Mark. Good luck with the new engine. Guess you'll be keeping the boat for a while, hey Buddy?
I can tell you that my wife's enjoyment of boating increased when she KNEW the engine would always start. Happy wife, happy life!

Hi Dave - yeah, we felt guilty sailing to these pristine places and on occasion we could see small amounts of oil on the water. Our Perkins was the prime suspect although it could have been something else. No more!

Yes, it makes the wifey much happier to have this reliability. And it signals our commitment to sail for at least another 10 years.

Hi Mark:
Congratulations on the new motor! It looks like it fits very nicely and a Yanmar is probably going to be the best in the long run. It also sounds like you spent about the same overall as we did for the Beta 38, but you are getting quite a bit more horsepower. So now I am second guessing myself and wish I had investigated the Yanmars more thoroughly. The folks I spoke to said a 3 cylinder would be the equivalent and I wasn't interested for some reason.

Thanks for explaining your thought process on a new engine vs rebuilding. It is quite an investment but spread over that many years it should be a reasonable amount per year, and will hopefully add to the resale value later on, and to do nothing was not an option. The hard part is deciding when you do the repower vs repair or rebuild. Just like for a car, keep it going or replace it? But deep down it is not dollars and cents, you don't like the old engine and want to get rid of it, so don't favor the repair and rebuild track. In hindsight five years from now it will be much clearer.

What prop do you have now, and what feathering prop would you change it for? I have the same thought but not sure what to get or how much advantage it would be. We have a 16RH12 three blade, probably the original, and Beta recommended 17RH11.
Do you plan any additional soundproofing?
Steve

Hi Steve - don't second guess yourself on the Beta. That's a darned fine engine with a long, great track record. Many, many devoted owners on the forums. The newer common rail Yanmar is a little more unknown but we decided to take the leap.

Yeah, I think if our Perkins was as well behaved as others on this forum we would have just done a re-build ... but we were sick of it and throwing money away. Pretty sure the poor thing was severely abused by a previous owner. It needed to be euthanized .

Our existing prop is a 16RH11 three (fixed) blade. It does OK, but I'm pretty sure I can get another knot of speed by changing pitch.

We don't race very much but I'm starting to get interested in folding/feathering props. Even cruising, they can shave hours or days off of long passages. I read an interesting article comparing folding/feathering props.

https://www.yachtingmonthly.com/gear/folding-and-feathering-propeller-test-29807

The FlexOFold came out very high on the tests. And Yanmar just bought the company so I was thinking it would be a good prop. After looking at it, though, I don't think we have enough space between the shaft and the forward edge of the rudder for it to fold up. She's in the water so I can't measure her now, but here is a photo. I think if those blades folded they would hit the rudder.




So now, I'm thinking feathering might be best, and I'm kind of zeroing in on the Max Prop. A lot of M38 owners have Max Props from what I can tell.

We do a lot of sailing in light winds and 2 knots of current. Especially when we are going against the current I've been told we can expect a 1+ knot speed difference when sailing with a feathering prop.

I think we still might do some soundproofing - not sure ... we need to take it for some real trips and see how it sounds. It certainly is nice not having everything vibrating off of tables and counters, though.

Steve, although my Perkins is still running well, I had a scare this summer and it makes me think about a replacement. Mark’s new Yanmar sounds pretty impressive and it’s torque numbers are quite remarkable. On the other hand, as he says, the Beta is a good engine and he is more comfortable with 21st Century technology than I am. So... can you tell me what rpm you run at cruising speed (6 knots)? What is the sound level at that speed compared to the Perkins or Yanmar you had before? Thanks.

Mark:
That is an interesting article about the propeller testing. Makes folding props look like the best for the money but I think you would have to measure very carefully to see if the folding one will hit the rudder. It appears that the feathering propellers will fit like a standard prop but a more expensive. Beta sells a feathering prop too but they didn't test that one. Any current pricing information?

Terry:
Cruising speed of 6 knots seems to be around 2200 to 2400 rpm with the Beta 38 with the 2.45 ratio transmission. Beta told our mechanic that they recommended a 17RH11 which would be an option to try.

I'm not good at describing the sound levels in words but at below 5 knots it is very quiet, at 5 to 6 knots cruising speed it is moderately quiet, maybe like the range of average car interiors at freeway speeds, but much quieter than the old Yanmar. There was almost a year from my last hearing the old Yanmar until hearing the new Beta so it is hard to compare them. At 6.5 knots it is loud enough that I remember thinking some sound insulation would be nice to add. A lot of the Yanmar's noise used to be due to vibration and rattling, which is pretty much gone now.

Steve

My Perkins is original--1980 and yes, she (or are engines he?) spills some oil and burns it when I gun the engine for close maneuvering. I pulled her and did some work when I bought the boat and she goes strong, pushing at about hull speed at 1800 which brings me to this point. If you have to run a Yanmar or a Beta at a much higher RPM, that must cause more serious wear and tear and possibly noise and vibration, but everything must work harder. Mass equals durability...or so I think ??? The Perkins is a "tank" so to speak. After reinstalling her, my ace mechanic said it would need a lot of cranking to fire up but it started instantly and he was shocked, saying "That never happens" Well it did..but she does leak. I am trying to learn about replacing the rear seals. Why not rebuild her rather than replace? Surely it would be much less than 20 boat units. As for the prop, I would sure like some real data and photos about folding or feathering as I don't think there is enough space in the aperture. Thanks!

Hi Paul - I was calling our Perkins a 'he' because I was thinking of him being a messy, angry old man. I think more highly of women . Yours sounds like a 'she' and I would have kept our Perkins if it was like yours and others on this forum. It's nice how we all get to choose our pronouns these days!

We had just thrown so much money into trying to rehab it, and the idea of throwing more Boat Bucks into an engine that is 1970 technology just didn't seem rational. Reliability is also important to us because of the voyaging we do. We could easily be in dangerous situations if our engine fails like it did on Labor Day.

All of us have different ideas, priorities, values, etc. and I'm not advocating that anyone do what I did ... I'm just sharing it as an information point.

I guess time will tell if my move was a good move or an idiotic one, or something in between. I wouldn't say that higher RPM necessarily means more wear & tear, since there are a bunch of newer technologies, materials, etc. I loved my beat up old 1968 Rambler, but I drive a Prius now, and it's the most amazing, reliable & fuel efficient car I've ever seen. And I can actually haul my dinghy in it!

Steve - I'm still waiting for a couple of quotes on feathering props, but I gather they are 2 to 3 boat bucks. I think we will have one in the future but I need to spend a little time recovering from the engine acquisition.

I was at the boat the other day and took soon measurements of the prop envelope. Probably a little different on length of the shaft but might give you a idea.

Perfect, Rick, thanks much!
I was going to try that in the water tomorrow but the visibility is not good.
Indeed, there is no way a Flexofold would fit. It has a 13” length when folded. I guess we are looking at a feathering prop instead.

Is yours a 16”? You didn’t get the measurement between the bottom of the prop & the skeg below it did you?
Thanks!

Check out a Kiwi prop Mark. No experience with it but thought I might try that as it was a whole lot less than a Maxprop/etc.

Mine is a 16" prop. I will get the measurement from the middle of the shaft to the bottom tomorrow. Once I snowplow a path to the boatbarn.
Any measurements that anyone needs I can get easily.

To Steve: if you go to a 17x11 prop you would be reducing the pitcH and increasing diameter, I believe. So, the boat would go in reverse somewhat better, but you would have to rev hgher to get you cruising speed. I can understand why Beta may suggest it, because all the manufacturers and mechanics say that diesels like to,be run at quite high revs on their power curve. So, contrary to what most of us might think, the more you run a diesel at high rev/loads, the longer they last. Idling for long periods of time is particularly bad for them. All that being said, the faster they go, the noisier they are, which is why we all run our engines at 2/3 WOT or thereabouts. Finally, and then I will end, several years ago my mechanic jacked my engine up in place and replaced the rear and front seals. It still leaks a very small amount now after 1600 more hours or so, but not as much as it used to. He said the problem is that Perkins still require some sort of cork seals and they don’t have the longevity of other material. I bet Mark’s new engine will never leak from its seals. Technology advances.

Terry,I have read about a adapter plate someone made that uses a lip seal inserted into it and than the whole unit must slide onto the shaft. Have you? Rick

THANKS....I had a good conversation with my ace mechanic yesterday--he pulled and reinstalled my perkins when I bought the boat--new mounts, shaft, cutless etc. He basically said keep running and enjoy him (her?) until she wears out. Yes..it will leak and it is not worth pouring money in to it or replacing with a rebuilt 4108. His advice is when the time comes, I will know it with "letters home" as he puts it. It will smoke more, becoming harder to start etc etc and just to run her at slow rpms. For the amount of hours I put on her, it will do fine...now If I were to run her for hours on end , say down the ICW, I run the risk of major wear and tear and breakdown...but even then...when the time comes, he recommends a new yanmar, vetus or beta--again getting newer technology as opposed to rebuilding the older. He suggests about 25k for new repowering....one never knows inc such cases if we make the right decision...but=--there are no guarantees!

Mark, from the middle of the shaft to the skeg is 11.25", bottom of the prop to the skeg is 2.5". My prop is 16 RH 11.

Rick, I have not heard of the adapter. If anyone knows, it would be TAD, transatlantic diesel.

Replacing the rear packing with an oil seal usually requires machining of the crankshaft. At least it does on an old British cars I'm familiar with.
Rear packing replacement requires experience to do properly. Today's marine mechanics may lack familiarity, so results can be hit and miss. Unlike a oil seal, the rear packing will never blow out. But it will never not leak either.
Consider that as your engine main bearing clearance increases from normal wear the packing becomes less effective as the crankshaft "wobbles". Nature of the beast!

Rick - thanks much for those measurements. They saved a lot of guessing and/or uncertainty.

FWIW. I installed an Aquadrive (essentially a CV coupling) which required moving the engine forward about 3". The 3QM30H sits on 6 Vetus liquid filled mounts. Really tamed the vibration. I chose a 4-blade VariProp (16x13) - adjustable pitch. The blades are a flat profile and although the prop moves the boat well it suffers from twice the cavitaion chop of a 2 blade as it passes the deadwood. If I had to do it over I would stick with a 3 blade. To compensate for the chop noise I have reduced my cruise RPM to about 1900. Slower but quieter.

John
With the 3QM30H, how did you find the room to move the engine forward 3"? Mine sits about 3/4" from the companionway steps. Did you modify the companionway?

Jim

Jim,
The engine box cover has been modified and extends about 4 inches with teak sides and top. I shaved 2 inches on the companionway treads as well. Darn thing is heavy though. We did not have a problem with the intrusion into the galley. The neat thing about the AquaDrive is that the thrust is transferred to the engine bed through the Aqua Drive bulk head bulk head and not the drive line. It accepts significant misalignment.
John `

John
I was just checking out the Aqua Drive website. It's really quite a system. Make sense to have the thrust going directly to the hull instead of the transmission. If you get a chance, could you post a photo of your build, including the bump out of the companionway. Did the engine rails have to be modified also?

Jim

Jim,
The systems been installed since the late '90's. I will get some pics and write up how I did the engine bed next week.

John

Jim,
Here's what it looks like 18 years or so after the install. I did not modify the rails except as shown in the pdf. 3 holes and bolts for each bulkhead support and 2 holes and studs each for the 6 Vetus mounts.

Another thing that’s nice about my new Yanmar is that it has a ton of NMEA 2000 outputs. This weekend I finally wired it into our NMEA 2000 backbone. So I can display oil pressure, temp, RPM, gallons per hour, nautical miles/gal, engine hours, etc on our chart plotter. Or because I installed a little NMEA 2000 wifi gateway I can display it on my iPad, phone or computer too. Thus I can be below in the cabin and micromanage my wife when she’s at the helm. She is gonna love that.

Here’s an example of when we were motoring @ 2250 RPM, consuming 0.95 gallons/hr. Speed thru the water was 7.1 knots. The engine was just purring along. This was our first cruise with the new (properly sized) propeller. We really, really like our new engine and Max Prop.

Hi Mark,
Beautiful display of engine data! Did your repower require altering the bedlogs for a different engine footprint and/or replacing the shaft for a a different length? Do you know if any of the engines have the same footprint as the 4-108?