Either one of those is going to require a lot of work to make them fit plus both are 3 cylinder and for sure will be rougher running than the 4 cyl M35A. Have you considered repair/rebuild? It may be something as simple as a head gasket leak. The M35A is a Kubota engine and they generally are very stout engines. Personally, I would look at a rebuild before swapping out for a 3 cylinder engine, even if it meant buying a complete rebuilt engine and giving them the old one for the core charge it's going to be simpler and better than either of the alternatives you're looking at.

Hi, Steve. I agree with Bud that a rebuild is almost certainly your best bet.

If you have compelling reasons to go to a different engine, it can almost certainly be done; it will just cost somewhere between a little and lot more than sticking with what you have now.

Good luck with your decision.

Sounds like it could be as simple as a blown head gasket; which is not a "serious" rebuild... (I've done my own gasket replacement on a Yanmar 18 cyl. from a boat I had in the 80's) and I'm no professional).
Have a qualified marine mechanic check it out before resorting to a new engine. Diesels are good for many thousands of hours before more "serious" rebuilds (total block rebuilds) are necessary.

Hi Stephen

Depending on your location and if you decide to go ahead with your engine retrofit project, I would be interested in obtaining your M35 for an overhaul project to replace my M25XP. But in my honest opinion, unless there is something tragically wrong with your M35, I would recommend you fix what you have, especially with such low hours on it.

Considering that the M35 is basically a Kubota engine, so everyone says I would have to believe parts are realitively available around the world. Most of these engines are rated for 3600 hours and I too would think it would be easier, less expensive to repair/rebuild.
Reading between the lines though, it sounds like you might feel the other engine choices would be better. I have found myself there before with my Catalina 30 (M25 3 cylinder)and with my 36 (M35 4 cylinder), mainly from the vibration. Currently I have that under control which was more the prop than anything else. I can personally attest the 4 cylinder is much smoother and quieter!
While you are repairing the head gasket get your injectors rebuilt at the same time and it wouldn't hurt to replace the gaskets on the exhaust manifold, send the heat exchanger to the radiator shop for a cleaning, and replace your hoses.

[quote=stephenemmerman;15772]did my homework looking at a beta 38 same kubota block as my m35 four cylinder. but will have my engine checked by a professional before i go forward.
thanks for your concern. about 1100 hours on engine but it is 16 year old.[/quote]

Stephen, it's really unlikely that the Beta 38 is the same block. The M35A is a V1200 Kubota block and it hasn't been built for many many years. The Beta 38 is based on a Kubota BV1505, is 1500 cc and weighs 168 Kgs, the M35A is about 1200ccs and weighs 150 kgs. That all suggests size differences and for sure the plumbing and electrical is not just going to be a bolt in.

Our engine is a year older than yours, 1167 hours, runs very well. I have one in my farm tractor, in industrial applications these engines easily go 5000 hours and 10000 is not uncommon. I would not consider replacing it as long as I can get spare parts. For sure I would never swap it for a newer M35B series engine or any other engine where the drive belt cannot be removed due to having water lines or any other obstruction in front of it. The Beta 35 and 38 are such engines, there is a steel pipe running from the water pump that blocks removal of the drive belt. Drive belts break and when they do you want to be able to change it quickly. They are good engines, but that one feature would stop me from having one.

Put me 2nd in line behind Tom to take your old engine off your hands!

Bud, I don't sense the risk to the drive belt as seriously as you seem to view it.

I do change the belt annually along with the impeller, keeping the old belt as a spare. Because July and August in the Pacific Northwest are months with rare winds, we can tally several hundred hours on the engine in a season. When I replace the belt after one of those kinds of season, aside from a small amount of belt dust, the belt looks like it could go another five years at least.

My M35B will pass the 2000 hours mark next year, and it's purring like a kitten.

[quote=LCBrandt;15784]Bud, I don't sense the risk to the drive belt as seriously as you seem to view it.

I do change the belt annually along with the impeller, keeping the old belt as a spare. Because July and August in the Pacific Northwest are months with rare winds, we can tally several hundred hours on the engine in a season. When I replace the belt after one of those kinds of season, aside from a small amount of belt dust, the belt looks like it could go another five years at least.

My M35B will pass the 2000 hours mark next year, and it's purring like a kitten.[/quote]

Yeah, I am hinky about that because once I had a brand new drive belt break when it had about 3 hours on it. It broke, naturally, at a very bad spot, rocky shore wise. But because there's no obstructions on the engine I can change it in 5 minutes, tops. I keep a spare belt right there at the engine that is 5 mm longer than stock and is super easy to get on and tighten. I guess when something like that happens it tends to shape your thinking, maybe too much?

The best fix for this, for me is to use the OEM style belt, which is a Dayco TopCog. I tried 3 Napa belts with bottom cogs on 2 different engines and not one has not made it to 25 hours without breaking or delaminating. The Daycos shed rubber for the first 10 hours, then they just settle in and work with very little dust and wear.

But isn't it a real pain in the butt to have to take a coolant line off to change the drive belt? That's a lot of hassle.

It's really not a hassle to remove a hose from the raw water pump on the M35B. All I need is a screwdriver, and I can have that hose off and back on in about, oh, 1 minute 30 seconds. It's a raw water line, so it's not under pressure.