Replace YSM12 with a 2GM20 or 3GM30 Move Posts

[Rick2413]

I'm replacing my YSM12 with a 3GM30F on my 1979 Hunter30 in the Spring. The foot print is slightly narrower on the 3GM30F. It appears at first inspection that the motor mounts will sit half on/half off the engine bed. I believe the 2GM20F and the 3GM30F have the same width. I understand many have done this repower but I have been searching the archives and internet for two days and can't seem to find specific details on the installation.My initial thoughts are to have extensions welded onto the steel engine mounting brackets on the engine where the motor mounts rest in.Good/bad idea?????
For anyone who has done the repower to either a 2GM20F or a 3GM30F on a 1979 Hunter30, what did you do to adapt to the engine bed? Was lowering or raising the motor on the bed to mate the engine/shaft couplers an issue as well?
I would greatly appreciate any photos, advice or links either emailed to me directly toyroom@ns.sympatico.ca or post a rely. Many thanks. Rick

 

[Hermit Scott]

Engine

Since alot of people looked at this but not responded I will give my $.02
I have a Catalina 30. I just rebuilt the YSM12 and reinstalled it. (I would have replaced it with what you are replacing your's with, but I'm poor)
When I find an old 3GM30 to rebuild, and I go to install it.
I will slide the hatch back and build a wooden truss in the opening. I will suspend the motor by straps that I can adjust, align the engine with the shaft coupler the best I can and modify the engine stringers(wooden blocks the mounts bolt to) and the motor mount plates accordingly.
I think it would be pretty simple to make new steel plates that bolt to the engine and then bolt to the motor mounts. (make them out of cardboard first) If you look on the bottom of the YSM12 you can see that there are steel plates that mount to the cast iron engine block and then to the motor mounts.
One thing I would do before I took the YSM12 out is to build, out of wood, a block that holds the shaft in place where it is NOW. I would screw that thing together and lock it down and not remove it until I had the other engine in and tightened down.
When I had my engine out I cleaned and painted the motor mounts and when I went to put them back in, I couldn't just put them back where they came out. I had to realign everything. The shaft will wiggle up and down and left and right to some degree. If you don't lock it in place before you remove the old engine you will have to try and figure out where center is.
As long as your old YSM12 was installed and aligned correctly. For example as long as you didn't wear out any flexible engine couplings or seals or flax packing leaking excessively. Then I would use the alignment you have right now with the shaft.
All this is dependent that you will not require a longer or shorter shaft. If you do I would make the wooden block for the shaft able to let the shaft slide in and out but keep it in position in all other degrees of freedom.
I hope this helps.Maine sail will probably come here and tell you I gave you a recipe for disaster.lol If he does listen to him not me.
I hear that this task you are undertaking retails for about $7,000. So if you don't have to call in the cavalry to rescue you half way through, you should feel pretty proud.

 

[Hermit Scott]

oh yeah

If you take the flexible tube off for your seal you can use the stern shaft tube to make sure you are centered. Just measure around it to see if the shaft is centered.
I wouldn't weld anything to the motor mounts. The steel is too thin. I would bolt something to the engine or existing plates and leave the motor mounts you have in place, in place.

 

[cbader]

I have another hunter 30 1978 in my marina that replaced his YSM12 with the 2GM20. They installed the new engine with new yanmar motor mounts. They also created custom mounts. I will see if I can get some pictures of the installation. The new mounts are very different than the old YSM12 mounts, also a lot less vibration and is quieter. I am jealous of his boat. Mine still has the 30 year old engine that vibrates and sound noisy but still keeps going. Good luck I got a bid to install a 3GM30 installed $13K just can't put that much in a $14k boat.

Good luck and will let you know about the pictures after the weekend.

 

[Seasick]

We repowered

our 79 H30 with a 18h Westerbeke. There engine bed was made narrower.