Tired Yanmar 1GM

[Cashbyvt]

So the simple little motor in my boat is looking like it has reached the time to do something about her. She is burning oil and lacking power. She's had a good run - she is almost 40. The question is, should I rebuild her or replace her with a newer version? The 1GM has a great reputation as a solid reliable engine and she is easy to work on. But would a newer motor be simpler? Would it run a little smoother or start easier? Would love to hear all your thoughts.

[Island Time O25]

No personal experience with newish Yanmars but am told by a very experienced mechanic (and a maintenance manager for 80+ boat sailing club for 10+ years) that new Yanmars are notorious for a) thin walls and b) corrosion prone electronics. His advise on old engines is always to try to rebuild before going brand new. His other advice is, if going new, Beta Marine would be his 1st choice as the parts are easily available from Kubota tractor dealers, incl. worldwide and are much more reasonable than Yanmar's. His 3rd advice is - do not install a Volvo or a Westerbeke.

[Cheechako]

Well, a 1GM ought to be very easy to rebuild. Is it seawater cooled only? if so then build up/corrosion could be an issue I suppose. IIRC Yanmar sells the piston and rod assembled. Not sure about cylinder sleeve etc . I think Sailor Chic rebuilt her 3GM by sleeving one cylinder which didnt have a sleeve. I imagine you can just lift out that engine by hand.
most 1 cyl run a bit rough, nature of the beast I think. A Kubota low HP 2 cyl might be cool. Not sure if they have a marinized one of those or not. I had one for a Generator I built, I think it was 12HP? Have you priced small new engines?

[Wotname]

Originally Posted by Cashbyvt

So the simple little motor in my boat is looking like it has reached the time to do something about her. She is burning oil and lacking power. She's had a good run - she is almost 40. The question is, should I rebuild her or replace her with a newer version? The 1GM has a great reputation as a solid reliable engine and she is easy to work on. But would a newer motor be simpler? Would it run a little smoother or start easier? Would love to hear all your thoughts.

There are many variables here.

A simple quick solution would be to replace it with a 1GM10; however I am not sure if they are available to the USA market as new engines. They are in Australia but I have heard they are not sold new in the USA; however I can't vouch for the veracity of this.

The new Beta's are very nice IMO but installation becomes more complex as mounts, exhausts, fuel lines, controls etc will all need moving or changing.

Personally I would rebuild the existing engine. While not super cheap, it is probably the cheapest solution but also the most labour intensive (if you are doing it yourself). The upside is all the existing ancillary bits and bobs remain the same and you know it will fit in exactly the same space.

If you have kept up the zincs in the engine, internal raw water corrosion won't be an issue.

Before making a decision, see what new engines are available (and cost) and price the following Yanmar parts for a rebuild.

IMO, the minimum parts needed will be:

Valves (both)
Piston & rings (probably oversize OR a liner - if available)
Big End bearing (undersized)
Wrist pin (gudgeon) bush
Main bearings
Thrust washer(s)
Head gasket
Paint
Rebuild the water pump at the same time

Then if the numbers seem OK to you, pull down the old engine and make a finial decision depending on what you see.

FWIW, I'm currently rebuilding an earlier Yanmar (YSE-8) and the process on the whole is simple and enjoyable but some of parts are pricey.

[Island Time O25]

Originally Posted by Cheechako

Well, a 1GM ought to be very easy to rebuild. Is it seawater cooled only? if so then build up/corrosion could be an issue I suppose. IIRC Yanmar sells the piston and rod assembled. Not sure about cylinder sleeve etc . I think Sailor Chic rebuilt her 3GM by sleeving one cylinder which didnt have a sleeve. I imagine you can just lift out that engine by hand.
most 1 cyl run a bit rough, nature of the beast I think. A Kubota low HP 2 cyl might be cool. Not sure if they have a marinized one of those or not. I had one for a Generator I built, I think it was 12HP? Have you priced small new engines?

My just sold boat I initially got with a seized original Universal (Kubota) 2cyl 11HP which I replaced with older 2QM15 because a) I had a good deal on the Yanmar and b) my friend the diesel mechanic said that my cost for the used Yanmar (which he checked and pronounced in good shape) plus installation would still be cheaper than just the parts for the Universal engine.

I did have to cut, re-position and re-glass the mounts but this wasn't too bad of a job (3 half days all by myself) and I consider it part of the learning curve anyway.

[GordMay]

Greetings and welcome aboard the CF, Cashbyvt.