Original to boat was 150 QSD (2.0 "Cummins" .... aka 80's BMW block converted by VM motori in Italy and resold through a Cummin Mercruiser deal in USA ) , it had been repowered after many hours by the original owners with a 130 QSD ( same engine de rated to 130hp ) , I purchased a few years after that but the second owners didn't have a clue about how to care for a boat let alone a Diesel inboard. It had been used and abused but much of it was missed during survey at purchase .... needless to say it was suffering excessive blow by, rear main leaks, etc shortly into my tenure with it .... it was my problem at that point so it was re-powered with a Betamarine 62T (2.4L) that I custom ordered and installed in 2024. Original engine 150hp would cruise at 12-13kts from what I've been told, 130hp would cruise at 9-11kts per my experience, now the 62hp Turbo Betamarine which is a Kubota 2403-m-t-eu4 engine cruises at 6-8kts all day.
Our use case was 95% of the time at hull speed so 6-7kts based on math for the R25c, so it works well for us and
SIPS the fuel .... sub 1gph at hull speed. I love the change and would do it again. I fully plan to get a faster boat when the time is right but for the family here in SE a slow boat is all that's needed for getting out and enjoying the area now. I could have gone with a Yanmar 110hp diesel but the waitlist was 18months and I am not a fan of overcomplicating marine situations with electronics. Plus per the math I would have only gained 1-2 kts max. The power required to increase speed over your hulls mathematical speed increases exponentially. You quickly realize that you have to toss a LOT of power aka fuel problem to go just a little faster. The new engine is rock solid old school mechanical ... aka EMP proof if that type of thing floats your boat, lol.
I really considered the outboard pods and doing smaller twins on it ..... it just was not cost effective once I looked into it deeply and started adding everything up. I would have also had to add a secondary fuel tank where the old engine was to compensate for the increased fuel burn outboards would have vs inboard Diesel. All that and I would have lost my engine heated cabin heat exchanger and hot water heater ... along with the Diesel source for my cooktop / aux cabin heater. Not that those things could not be fixed, I just decided it was not worth the effort for what I really wanted in the end.
Im interested to see what you end up doing! Good luck.
Link to Beta engine I used with some custom stuff ordered also. Checkout my profile posts for photos of my install. TMC345A gearbox, shallow sum oil pan, rear PTO driven raw water, remote oil filter , British green paint since I dislike the red color, etc ....
betamarineusa.com
last re-power followup thread of mine .... with photos.
I am thinking the QDS had electronic throttle and shift. Did you need to add mechanical throttle and shift with one lever or did you split them?
the QSD has electronic throttle connection on the port side of engine and gearbox has cable shift ( ZF25A ) both are morse type cable from the helm however. No changes needed there. I did however replace both the throttle and shift cables with the repower as they were getting a little stiff.