Arctic Fox
New member
Hi all,
I am based in Kent, Uk and have owned a 32 foot twin diesel cabin cruiser since 2003. The boat is fitted with two Chrysler Nissan SD33 6 cylinder diesels coupled to Chrysler badged, Volvo Penta 275 outdrives with ratio 2.15:1 and 16 inch diameter by 21 inch pitch props.
The boat has a displacement of between 5 and 6 tons, has a medium V semi-displacement hull 32 foot long and 10 foot across the beam.
I mainly use the boat on the river but occasionally take it out to sea. The performance at speed is poor and I suspect that the outdrive ratio and or the prop spec is not correctly matched to the hull. The 21 inch pitch seems excessive for such a boat. At river cruising speed of 5kts the engines rev at around 1350rpm which is ok, however at max throttle the boat reaches only 10 kts at around 3000rpm max. I tried 16 x 17 props but the performance was much worse with high 1500rpm for 5 kts. From some estimates based on the current set up and the limited data from the 16 x 17 prop runs, I guess the boat would perform much better with outdrive (sterndrive) ratios of perhaps 1.89:1 with 16 x 19 props or even 1.61:1 with 16 x 17 props. Any thoughts on this? Is there anyone out there with a similar size and spec boat also with twin SD33 diesels and sterndrives? If so what ratios and props do you run and what performance do you achieve (slow speed engine revs at say 6mph (5kts is 5.75mph) and max speed with max engine rpm?
I am based in Kent, Uk and have owned a 32 foot twin diesel cabin cruiser since 2003. The boat is fitted with two Chrysler Nissan SD33 6 cylinder diesels coupled to Chrysler badged, Volvo Penta 275 outdrives with ratio 2.15:1 and 16 inch diameter by 21 inch pitch props.
The boat has a displacement of between 5 and 6 tons, has a medium V semi-displacement hull 32 foot long and 10 foot across the beam.
I mainly use the boat on the river but occasionally take it out to sea. The performance at speed is poor and I suspect that the outdrive ratio and or the prop spec is not correctly matched to the hull. The 21 inch pitch seems excessive for such a boat. At river cruising speed of 5kts the engines rev at around 1350rpm which is ok, however at max throttle the boat reaches only 10 kts at around 3000rpm max. I tried 16 x 17 props but the performance was much worse with high 1500rpm for 5 kts. From some estimates based on the current set up and the limited data from the 16 x 17 prop runs, I guess the boat would perform much better with outdrive (sterndrive) ratios of perhaps 1.89:1 with 16 x 19 props or even 1.61:1 with 16 x 17 props. Any thoughts on this? Is there anyone out there with a similar size and spec boat also with twin SD33 diesels and sterndrives? If so what ratios and props do you run and what performance do you achieve (slow speed engine revs at say 6mph (5kts is 5.75mph) and max speed with max engine rpm?