CD25D repower 1GM to 1GM10?

[Skipd]

My 1GM has been pulled from the boat and an estimate for a partial rebuild is being put together. Has anyone replaced a 1GM with a 1GM10? If so, was it a one for one swap, same prop, same motor mounts and positioning, etc? Was the increase in HP worth it?
Also, would you know if the new B panel (with digital read outs of temp, oil, etc) works on older Models?
Any help or advice is appreciated. Thanks

[Gary H]

While you have the engine out, consider replacing the engine mounts, shaft log hose, cutlass bearing and possibly the prop shaft. You will not want to take the engine out again. When I did this, I was amazed at the difference in the flex of the rubber between new mounts and 20 year old mounts. Almost no vibration whatsoever with new mounts.

When I removed my engine for repair, one thing just seemed to lead to another. I am glad I did, as I hope to not have to take the engine out again.

[David Morton]

I've got a 1GM in my 25D. If I were to re-power it certainly wouldn't be to another antique! The 1GM10 is the same engine as the 1GM, just bored out to a larger cylinder and no longer in production. I'm not sure it is worth it to gain just another 2 hp and like others have said, it's not something you want to do twice! Having said that, I do think the 25D, at least, is underpowered with the 1GM. If I were to go to the trouble of re-powering it would be to a contemporary dual cylinder diesel, perhaps a Beta Marine 14, which has been used by others to replace the Yanmar 1GM, with minimal modification of the engine bed and compartment. If you are wedded to the Yanmar, perhaps a re-build of your current engine would make the most sense. I also agree that a good exam and possible replacement of all the peripherals ( mounts, stuffing box, bearing, shaft, prop) would be wise.

Good luck,
David

[Jeff G]

The 1GM 10 is an over-bored 1GM. All mounts line up correctly, uses the same tranny and shaft. I had my 1GM rebuilt. When they rebuilt it they rebored the cylinder for a 1GM 10 piston and replaced the cylinder head with a 1GM 10. So essentially, it became a 1GM 10. I did not change the prop. She runs at about 2800 RPM. The advice about replacing hoses and motor mounts is well founded. I did replace my motor mounts and hoses. I cannot comment on the panel as I reused my old one.
A fresh water cooled 2 cylinder replacement is probably better in the long run but rebuilding is more cost effective than a full repower with a Beta Marine. It should run for another 20 years.

[joemerchant]

Would a 2GM not fit in there? The 2GM is night and day a better engine and on our old boat we were very happy with the change.

[Jeff G]

Would a 2GM not fit in there? The 2GM is night and day a better engine and on our old boat we were very happy with the change.

It will fit but it is a lot heavier than a 1 GM. In a 25D weight is a big factor. The 2 GM is a nice replacement for a CD 27 or a CD 28. The beta Marine is a little bit heavier but not as heavy as the 2 GM. Both engines will need to have engine bed modifications to fit properly in the 25D.