Mariner 40hp ex navy mid shaft rpm range

[1eyedjim]

hi
i have got the above engine on my 4m searider and took it for its first outing last weekend
flat out with me and the mrs on it was reving to approx 5600-5700rpm
with me and 2 others it was about 5300rpm
these seem a bit to high to me so i think i will need a larger pitch as it will mainly be used by me and the mrs and occassionally a few others. it has a 13" at the moment so would a 15" sound about right?
another question is idealy i want a stainless prop for it but have heard tails about if a 15" alloy prop is correct then i would need a 16"-17" stainless due to the extra weight and better efficiency of the stainless...... is this true or do i just get the same?

cheers
Jim

[Nos4r2]

Stick a 15" on it.
If you're going to put an SS prop on it, get yourself the right pitch ally one 1st then drop down about an inch of pitch (so probably a 14") for the stainless one. Personally I wouldn't bother though.

[kev]

Hi there what kind of speed were you getting with the 13" prop ,I can just get 30 knots with 2 up but think its reving to high I have a 40 mariner 2clynder 2 stroke.was thinking of changing to 15" pitch prop.

[1eyedjim]

havent got a speedo on it yet so unsure just got the rpm guage, will hopefully have a gps speedo on it next time i use it so can feed it back