Not achieving min WOT??

[mtjbrown]

My motor a 95 75 hp Mercury 2-stroke is only achieving 4400 rpms a WOT. Does this sound like I need to change prop pitch?? Currently running 13.5" x 15 pitch aluminum as recommended by boat dealer. I had an issue with the switchbox being bad, I fixed that motor runs smooth. I don't know my speed but its an 18' pontoon boat. I found the specs online WOT throttle is 4750 to 5500 rpms.

 

[The Rooster]

Re: Not achieving min WOT??

A 15 pitch may be a bit large for a 75 hp, but you need to verify accuracy of your tach, then possibly consider raising the motor a notch or two. If your cavitation/anti-ventilation plate above your prop seems like its running well below the surface while your cruising, you should be able to raise the motor. If thats not the case, its time to look at a smaller prop. Good luck !!!

 

[mtjbrown]

Re: Not achieving min WOT??

I thought about raising the motor but if I trim it up much at all, it seems to be ventilating! Tach goes to 5500 rpm and the speed drops way off. Should have mentioned that in the first post. Should I drop to a 13???

 

[Rancherlee]

Re: Not achieving min WOT??

Yes, a 13 should get you to around 5000-5200rpm or so, being a carbed 2 stroke I might even suggest a 11 pitch even though I might over rev a touch with a light load.

 

[mtjbrown]

Re: Not achieving min WOT??

Thanks for the replies, guys! I may try to round up a 13 and check it out. I am concerned if it is lugging the motor with the 15 on there. wouldn't that be bad for the motor??

 

[The Rooster]

Re: Not achieving min WOT??

Thanks for the replies, guys! I may try to round up a 13 and check it out. I am concerned if it is lugging the motor with the 15 on there. wouldn't that be bad for the motor??

Yes, over time, it's not good for the motor. Good luck !!!