Prop swap?

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Prop swap?

Postby CPLucasMA on Sat Apr 13, 2019 8:12 pm

I have a 2015 25-SC, with a Volvo Penta D3.

Has anyone swapped the factory prop for a different prop? Would love to hear suggestions.

I understand the D3 should max out at 3000 rpm, but I can only get about 2750 with a max speed of about 12 to 13 knots, with empty holding tank, half fresh water, half fuel, and painted but clean hull.

Wondering if a prop change may help.
Christopher Lucas
Lucas Electrical Services LLC
PO Box 431
Salem, Massachusetts 01970
Posts: 11
Joined: Thu Feb 27, 2014 6:25 pm
City: Essex
State/Province: MA
Ranger/Cutwater Model: R-25 SC
Non-Ranger Model: Wilderness Systems, Current Designs, Winonah, MR
Vessel Name: Zoftig

Re: Prop swap?

Postby Salty7 on Sat Apr 13, 2019 9:11 pm

I don't know if the max rpm number you have is correct for that Volvo, I'm sure someone will confirm it, assuming it is correct a good prop repair shop can remove some pitch and get you up to max rpm. You will probably need about an inch less pitch. Make sure the bottom is clean, double check your maximum rpm and give the figure to the prop shop. All the diesel mechanics I know say a boat with a modern diesel should get to max rpm with the boat fully loaded the way you operate it. As the weight comes off the boat as you burn fuel, use water etc that just takes a load off the engine. You cannot overspeed a diesel, it has a governor to prevent that, if you overload it though by having too much prop pitch, it is constantly overworking and off it's fuel and efficiency curve, which is very bad for your engine.
Posts: 51
Joined: Sun Jul 29, 2018 9:06 am
City: La Conner
State/Province: WA
Ranger/Cutwater Model: R-25 SC
Vessel Name: KIKI (2012) Yanmar 4BY2-150

Re: Prop swap?

Postby S. Todd on Mon Apr 15, 2019 10:32 pm

We also have a 2015 R25SC with a Volvo D3-150. The rated RPM is 3000 and we get that with the factory prop, half full fuel and half full fresh water 2 people a dog and light cruising gear and about 18 miles per hour. Fully loaded we only turn about 2930 and 17 miles per hour. At 2400 we get 13 miles per hour until the fuel tank gets down to with a third of empty when she does 14 miles per hour. Factor to convert knots to miles per hour is 1.15 if memory serves me correctly. Our bottom is clean with no paint which I understand makes about 1 mph difference.
S. Todd
Posts: 236
Joined: Tue Jan 27, 2015 10:09 pm
City: Indianapolis
State/Province: IN
Ranger/Cutwater Model: R-25 SC
Non-Ranger Model: Zodiac Cadet Aero 230 & Innova kayaks
Vessel Name: Audrey Rose (2015)
MMSI Number: 367722240

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