1999 Force 75 on pontoon

[hobble222]

I have a 2000 Fisher 200DLX 20' pontoon boat with a 1999 Force 75. My current prop is a 13.75D X 15P aluminum--slightly damaged. Max rpm (lightly loaded--2 people, 1/2 tank fuel, minimal gear) is 4400. I believe this motor should run 5250 WOT. Performance is not terrible--gets up good, GPS speed is ~21-22mph--but I think a different prop could make a difference. Any suggestions? I am looking at all avenues--change in diameter, pitch, composition. Also, where do I get a new prop?

 

[steelespike]

Re: 1999 Force 75 on pontoon

Not an expert but it seems your speed is pretty close to what you could expect.Repaired prop might get a little more speed.It will be tough to make up 800 rpm with a prop.Though you say performance is pretty good you might check for full throttle opening,maybe check your compression.I believe there is a timimg setting you need to check as well.Also you may need to raise the motor vertically a little bit.A good sound prop will help combat ventilation which can be a problem on a pontoon.There is also the possibility the tach is incorrect.If the motor is truly lugging at 4,400 rpm it is very bad for it and you should try to figure out for sure where you are at.Start with a prop repair and maybe a local marina has a portable tach you could use especially if you mentioned wanting to change props.

 

[moderator1]

Re: 1999 Force 75 on pontoon

That should have about a 13p, maybe even 11p.<br />When RPM is that far below normal range, 2" of pitch can change the RPM by 800-900 easily because the motor is not running near max torque now.<br />I'd look for a 13P aluminum 3-blade.<br />Take a look at our iboats prop finder..

 

[hobble222]

Re: 1999 Force 75 on pontoon

Thanks for the replies. I have verified that the carbs are fully open but have not checked compression or timing. The tach is a Teleflex Sahara set to 6P--correct for all 3 cylinder outboards. I have not tried a different tach to verify though. Raising the motor is interesting--tilting up(like trim) can raise rpm by ~100rpm--but produces different(not better) ride characteristics. Getting more straight up out of the water could be beneficial. To drop to 13p or 11p would require a change in diameter(I can't find a 13.75 X 11 or 13). What effect does this have on the motor?

 

[walleyehed]

Re: 1999 Force 75 on pontoon

Diameter of a given design changes with pitch...<br />It's normal for the diameter to increase as pitch decreases.<br />11 or 13 would be a 14" diameter, I believe.<br />I think I would go with a 13, especially if I could get one to test and return.