Correct prop for a 180 Forester with 125 Force

Spivy30

Petty Officer 1st Class
Joined
Jul 19, 2008
Messages
299
I am trying to figure out what is the problem with my boat it is a 1986 Forester 180 Phantom with a 1985 or 1986 Force 125 with just myself in the boat and a 1/4 tank of fuel I can only get 32 mph out of the boat on the gps and a wot of 4100rpms
The prop has no size stamped on it but on the hub it says "michigan 072107" so I checked to see if that was a michigan wheel number and it was a 17pitch prop for a force outboard. I just dont understand how the boat could be so slow. According to a forester brochure it says the boat weighs 1090 pounds without motor so I figure about 1500 pounds with motor and fuel to be on the safe side. My dad had a 1985 bayliner 19 Capri with the same motor and it did close to 50 mph.
My guess is the boat is totally proped wrong but i've read so many different things I dont know what to believe. I would also like to add that the boat has 150lbs of compression in all 4 cylinders, new plugs, and runs on all 4 cylinders.

Can somebody please help me
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Correct prop for a 180 Forester with 125 Force

You might start by weighing the rig,be sure throttle opens all the way,Be sure timing and sync are right.Fine tune your setup.Starting with the anti vent plate even with the bottom of the boat raise the motor a hole at a time to a point just before venting becomes a problem.Be sure it pumps water.
I think your fathers speed is a little optimistic.If I got his rig to 45 I would be really happy.Your boat with a 17 pitch I would think could manage the high 30s to low 40s.You obviously need about 1400 rpm.See if you can confirm prop is a 17.Perhaps ask a prop shop to measure.Props have been known to be fiddled with.
 
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