Which Engine?

[meyermm]

Originally Posted by Mark Zarley

Just another thought , Buy by the pound. Divide eng weight by hp . One might logicaly assume that the heavier the hp the tougher the eng. There is a reason some engines are called "tinney". I think cummins bought perkins.

Very novel having been in the automaotive repair business for over 40yrs I thought I had heard it all.
Most engines are well made these days and when I hear of trouble I usually look carefully at the operator for the source of the trouble. Yanmar builds very good purpose built marine engines that when installed correctly and operated properly give a minimum of trouble. No more than any other brand and probably a lot less. Boats are not like cars in that the motors are not designed for a particular vessel hence incorrect installation can cause on going troubles which the engine gets blamed for. People never like admitting they may have taken a short cut (money cut) with the installation or service procedure.
As for high speed vs low speed diesels, technology changes but convincing buyers that a newer design is superior is hard work and some times impossible. Some of the engines spoken about on this forum I would only use as an anchor, but others love them!

[Cheechako]

For me it's all about the power curve. If I'm buying an engine I'm going to compare all the candidates at the same RPM regardless of what they rate the engine at RPM wise. The Yanmar 4JH4 "54 hp lightweight" engine is 27 Hp at 2400 rpm, the Perkins 82 HP 4-236 is rated at 82 HP at 2600 rpm. It's pretty easy to see where much of the "lightweight" comes from, it's really a smaller engine. I'm not saying they are not good engines,they are pretty good engines. I just think it's deceptive... I ran my catamaran at the Yanmar approved, and Yanmar mechanic recommended 3200+ rpm and both engines failed.

The perkins 4-236 is evidently still available here: TAD for Perkins 4.236 Diesel Engines, Perkins 4.236 Diesel, Perkins 4.236 Marine Diesel, Perkins 4.236 Engines

[lancelot9898]

Originally Posted by Cheechako

For me it's all about the power curve. If I'm buying an engine I'm going to compare all the candidates at the same RPM regardless of what they rate the engine at RPM wise. The Yanmar 4JH4 "54 hp lightweight" engine is 27 Hp at 2400 rpm, the Perkins 82 HP 4-236 is rated at 82 HP at 2600 rpm. It's pretty easy to see where much of the "lightweight" comes from, it's really a smaller engine. I'm not saying they are not good engines,they are pretty good engines. I just think it's deceptive... I ran my catamaran at the Yanmar approved, and Yanmar mechanic recommended 3200+ rpm and both engines failed.

That brings up an interesting point about the commonly accepted thought about sizeing the prop so as to achieve the rated rpm setting at WOT. I've operated my 1985 Perkins 4-108 for almost 25 years at much less than the rated setting (3600 rpm). In fact my WOT rpm is only 2300 and I operate normally at 80% of that number. As long as I achieve operating temperature and operating up on the torque curve, I see no problem. Also the WOT rpm will change depending upon if the boat is tied to dock, operating in open water, or operating against a swift current. The WOT rpm should increase as one moves from being tied to the dock into the swift current because there is less resistance on the prop at a given rpm.

[pelagical]

Professional Boatbuilder Magazine had an article this month on "Niche Diesels" mentioning Beta and Steyr as companies that specialized in refits. simple rugged and reliable engines not sensitive to bad fuel,etc. Professional BoatBuilder magazine

[Cheechako]

yea... it's pretty fuzzy how they do this.... . Your 4-108 might have been rated at a lower max rpm if it's application was commercial use, but rated at the 3600 rpm for Recreational use.... that should tell you something.... I believe if I had propped the Yanmar's in my catamaran for lower RPM, and bought the correct HP for that rpm, I never would have replaced both engines in less than 2800 hours...

[neilpride]

Originally Posted by Cheechako

yea... it's pretty fuzzy how they do this.... . Your 4-108 might have been rated at a lower max rpm if it's application was commercial use, but rated at the 3600 rpm for Recreational use.... that should tell you something.... I believe if I had propped the Yanmar's in my catamaran for lower RPM, and bought the correct HP for that rpm, I never would have replaced both engines in less than 2800 hours...

You mean that you replace both engines with 2800 hours?? can i ask why??

[Cheechako]

The first one failed completely and Yanmar replaced it. The second one had a cracked piston, but ran OK at higher RPM. I had to have that one overhauled at 2800 hours. ALl new pistons....

[SteveHoiland]

For me it was what fit for a repower. The engine enclosure was narrow and the Universal M40-B, 38HP fit the bill. It's my oppinon most of the units out there will do the job. The M-40b is based on a Kubota block. It's much less vibration than the old 3QM30, 33HP Yanmar

[Cptn Happy]

Beta has a good reputation. They make a 75 and 90hp model based on Kubota blocks. Might fill the bill.

[Morganministry]

My vote would be for a Kabota or John Deere.
My experience with Kabota comes from a 12kw Diesel Generator that was used to power the service landing for a Helicopter outfit that I worked for. The Kabota Generator ran 24/7 only being shut down once a week to change the oil. And it was being ran on Jet fuel which is like Kerosene and does not have the lubricants that Diesel has. The Generator was in use when I started working there and was still being used when I quit 4 years later. We never had a problem with it.
My experience with John deere has also been good. Mainly with tractors. I haven't had any problems with the engines. The company has a good reputation and they are great to work with. And they have parts available world wide.
Thats my 2 cents,
Scott

[meyermm]

Running those Yanmars at 3600rpm sounds like high RPM to me which would account for piston failure. I would be interested to know what Yanmar technical made of the whole saga. Bad batch of pistons? Incorrect RPM vs load? Yanmar has a very good reputation but so does Mercedes and they have had some dramas in recent years.

[Stillraining]

I wont have an engine that wont handle normal abuse..Have read many accounts on these forum that owners have explicitly been told not to Idle yanmars for any length of time...That scratches them off my list right there.

Now having said that I know nothing of them and don't know if it really does harm them or not...but everybody seems to get all excited about it.

I have several of each of John Deere's, Case, ( Great engines by the way ) Cummings, Perkins, Kubota, Isuzu and yes even 2 cycle Detroit's ( not supposed to Idle them either so they say) they have ALL idled for literally months and months of there lives and a few have gone over 10,000 hours without a hiccup so far.... All but one are over 4500 hours.

Nope give me the boat anchor any day.

[meyermm]

You no the old saying a little knowledge can be dangerous. You should not idle any brand, it can cause bore glazing. The same as you should not use multigrade oil in most of these engines, same reason. Just because you have been lucky does not make it right. I have pointed this out to some at the marina with brand?? engine but most think they know better than the engineers who design them and write the manuals. Remember sales people will tell you what you want to hear they just are after your sale and then any problems related to operation becomes someone elses problem to solve. So if you want to idle they will tell you that's fine. Are they oil specific oh no any oil will do just sign here.

[Stillraining]

LOL.....ya well my little dangerous bit of knowledge works for me...it has to... I have to get up in the morning and fire up two of those poor abused engines and work them tomorrow..both of them will Idle for at least 3 hours tomorrow..

If I told you how often I change the oil in my cars you would not believe it either..

Cheers mate

[bobfnbw]

I chose to rebuild my perkins 4-108 rather than install a new engine.
1st was cost. The new engines would require a complete bed replacement, bigger exhaust, and overall more cost.
2nd was size. My boat was designed around a perkins, figured it lasted this long, might as well go another 25 years or more with it.

But the cummings engine sold by TAD looked mighty good. I almost went for it. The power curve it where I need it, not at 3500 rpm.
My rebuild cost me almost 15000 when all was done. Including the price the yard scalped me on pulling the engine, and replacing it. Crazy. But I could not do it where I was, and I had to get her done, so... I paid.

Life's little lessons.

Bob