mercury 90 force equivalent for propeller

[iulian]

My propeller is dia 12-3/4 with 21 pitch, and I have one more propeller with dia 13.5 and pitch 15
Can I replace it with the the second one with 15 pitch on my boat?
Mercury mariner 1996, 90 force
Thanks

 

[Chris1956]

Re: mercury 90 force equivalent for propeller

Iulian, Normally prop diameter increases when pitch decreases. Therefore that 15" pitch prop should be larger in diameter than the 21P prop. Sounds to me like it is the correct prop, assuming the splines are the same and the prop hub is the same diameter.

 

[hwsiii]

Re: mercury 90 force equivalent for propeller

Iulian, that 15" pitch should work fine, depending on the differences between blade geometry in those props. So long as you are pulling a LARGE hippopotamus on a tube behind the boat while you are using that prop. LOL :laugh:

Seriously, with that much change in pitch between the two props, even taking major blade geometry differences into account, if the 21" pitch is running about your maximum RPM's you should be able to easily bypass the maximum RPM's for your motor, so just be sure that you hold back on the throttle. But you should experience a superb hole shot.

H

 

[Silvertip]

Re: mercury 90 force equivalent for propeller

The short answer is NO. As always there is a "BUT". If this motor is on a pontoon or work barge then it could work. If it is on a planning hull then no as the engine will overrev by a bunch. Consider this: A standard 40/50 Non Big Foot Merc uses a 1.83:1 gearset in the lower unit and a typical prop for that engine is 10-1/2 x 13P. A Big Foot motor uses the same 2:34:1 gear set as the 75 & 90 HP engines and a typical prop for them is 13-3/4x19P. Therefore, 4 inches of pitch change results in 800 more rpm (and likely then some due to the virtual absence of loading) and serious over reving. Just because it fits, does not make it OK to use.

 

[iulian]

Re: mercury 90 force equivalent for propeller

thanks, what do you think about 22 pitch with 14-1/2 dia?

 

[jestor68]

Re: mercury 90 force equivalent for propeller

thanks, what do you think about 22 pitch with 14-1/2 dia?

No can do. The largest diameter prop that will fit on the intermediate size gear case is 14 inch.

Without knowing what WOT rpm it turns with the present prop, there is no accurate way to judge what size(pitch) you might need.

A visit to the prop section will tell you what sizes are available for your motor.