How many original Cummins/Mercruisers still running?

NorthernFocus said:

After 16 years and almost exactly 2700 hrs we pulled the plug. In the process of installing a Yanmar 110hp.

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I have a recently repowered 2010 R25 SC. It went from a Yanmar 150 to the Yanmar 110hp. Same marine gear. I suspect repropping with the right prop might be better in the long term. The old 150 ran to 4000rpm. My sweet new 110 is speced at 3200rpm but willingly wants to exceed this at WOT. Original prop was a 17x 13. When the Classic came with a 110, it came with a 17 x 17. Not sure if the marine gear had a different ratio.
Did you reprop? If so, what did u use and how is performance? Say speed at WOT, rpm/mpg at hull speed? Wondering if it’s worth the $1700 plus shipping. Thank you in advance.

ciaran said:

I have a recently repowered 2010 R25 SC. It went from a Yanmar 150 to the Yanmar 110hp. Same marine gear. I suspect repropping with the right prop might be better in the long term. The old 150 ran to 4000rpm. My sweet new 110 is speced at 3200rpm but willingly wants to exceed this at WOT. Original prop was a 17x 13. When the Classic came with a 110, it came with a 17 x 17. Not sure if the marine gear had a different ratio.
Did you reprop? If so, what did u use and how is performance? Say speed at WOT, rpm/mpg at hull speed? Wondering if it’s worth the $1700 plus shipping. Thank you in advance.

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I haven't run the new engine yet. As a matter of fact I just brought the boat home from the shop yesterday. The various calculators I've run looks like my existing 17x14 .105 cup prop is really close. I've also got a spare with 15 pitch. Hopefully will test it before too much longer.

NorthernFocus said:

I haven't run the new engine yet. As a matter of fact I just brought the boat home from the shop yesterday. The various calculators I've run looks like my existing 17x14 .105 cup prop is really close. I've also got a spare with 15 pitch. Hopefully will test it before too much longer.

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Thank you. I got to speak with a boatyard guy and yanmar dealer yesterday at the Anacortes boat show. We talked rpm’s, boat speed and other performance that I’ve seen so far and he said that the old 17 x 13 seemed to be performing solidly in the acceptable range and that going 17 x 17 would perhaps bring incremental change but seeking lower rpm at hull speed might not be a good thing. As an aside, He said that there was a risk of carbon buildup running lower rpm and recommended running North of 2000 with at least 5-10 minutes of 3000+ hourly. I think I’ll keep my 2K propeller money for other stuff. I’d be interested in hearing how your repower performs though