I think I have the wrong prop for my 40 hp TLDI

bnoody

Recruit
Joined
Feb 26, 2009
Messages
5
I have a 40hp Nissan TLDI motor on a 17? glass boat. Fully loaded it is not reaching peak RPM range recommended by the manufacturer. The motor currently reaches 4700 RPM?s and should be in the 5150 ? 5850 RPM range at WOT.

I have a 12 pitch Michigan wheel prop on it currently and think I need to drop down to an 11 pitch prop.

Couple concerns I have, does running the motor wide open and not reaching peak RPM?s due to excessive load harm the motor? Will I lose top end by dropping to an 11 pitch? I suspect the increase in RPM will increase top end because it is below recommended range.
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
Re: I think I have the wrong prop for my 40 hp TLDI

You need to drop down to a 10 pitch at a minimum as you are presently lugging the engine which cuts down on its life. You will probably lose 1 to 2 mph at top end, but you will increase your take off power.
 

inPursuit

Cadet
Joined
Mar 10, 2009
Messages
16
Re: I think I have the wrong prop for my 40 hp TLDI

Dropping to either an 11 or maybe even a 9 pitch will make a world of difference for you. You might even gain a little speed on the top because the added RPMs will compensate for the less pitch.
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: I think I have the wrong prop for my 40 hp TLDI

Bnoody, here is what your new numbers will be if you drop your pitch to a 10" from the 12" in the same series of prop. It will be running right in the range for your motor, so it will not be lugging any. Hope this helps.

BnoodypropIboat.jpg



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