Yanmar upgrade

[milltech]

I used to own a Fredk Parker little motor boat, 25 foot. Originally she had 75 hp petrols but around 1992/3 she was converted to Yanmar diesels of 50 hp. She's semi displacement and needs extra umph.

Am I right in thinking the same Yanmar block goes goes up over 100 hp? Could I use the same gearbox?

Anyone upgrading a pair of larger Yanmars let me know, I think 80-100 horses would do very nicely. The man I sold this boat to has offered it me back four years later and it's not very interesting but might make a smoker for me until the real thing comes along as the song says.

John

 

[Chris771]

John,

I imagine that you are referring to 4JH engines (believe they are about 1800 to 2000cc), don't know much about them, but suspect that the similar criteria applies as to the larger 3500cc 4LH /LTE/HTE/DTE etc.

In the 4 LH engine, which I had in Polar Fox the same engine ran in various guises from 120 HP to the HTE 140 hp (which I had) to 165 and 230 hp.

I did look at uprating mine to the 165 HP version, thinking that it was possibly just a matter of changing injector nozzles or adjusting injector pump relief pressure and turbo boost.

However it was not anywhere near that simple, my research showed that the modifications required a different pump and different injectors plus a plethora of turbo bits to increase the boost pressure. The 230 hp engine had a different turbo and increased diameters of almost everything and larger intercooler

The cost was going to be ££££££££££££ Brewsters and definitely not economically viable. It would probably have made more sense to have sold the existing engine and looked for a secondhand uprated version.....but then you never know what you are buying.

In the end I decided that as my engine was well below 100 hours when I bought her, it was realistic just to keep it as was and forego the extra 2 kts I would have gained.

Chris

www.impact-computers.net/boat/cruiser.htm

 

[milltech]

I casually asked similar questions when I owned this boat before and I'm sure an engine swap would be the best way, either upgrading for new with a Yanmar dealer or just finding someone who was changing.

I would like confirmation, but I think it's so, that the larger engine would sit in the same engine bay on the same engine beds etc.

John