no power

[host]

i have a 20 ft trophy walk around cabin model. put a 115 hp mercury 4 stroke on it. can anyone tell me what pitch prop to use. had a 17" no power at all put a 15 0n it still very slow at getting up on plane. sorry no tach but it hasnt hit the rev limiter. motor is new. thanks host

 

[steelespike]

Re: no power

Do you trim in for hole shot?Is the initial trim set right?Is the bottom clean and smooth?
Without actual rpm and speed can't really tell where the problem is.I don't think it is prop related.Check the motor height.the antivent(cavitation)plate just above the prop should be slightly higher than the bottom of the boat.use a straight edge extended from along side the keel.Don't assume all is right because its new.
It wouldn't be the first new motor with a plug wire off, the throttle adjusted wrong
or the motor installed way low.

 

[host]

Re: no power

the cavitation plate is level with bottom or 1/2 inch above. reason i think its prop is with a 17" there was no power with a 15" it will get on plane just not fast. took to the dealer put it on the computer and they said everything was perfect. I will get a tach. should run at 6400 rpm. maybe a 14" prop?

 

[junior1113]

Re: no power

that sounds way under powered. esspecally a 4 stroke. what was on it?
if you went down to a 13 max speed would be slow. tach is a must for outboard proping. i see 20" trophy walk arounds all the time with 200, 175,150engines but never a 115 four stroke

 

[trendsetter240]

Re: no power

It does sound a bit under powered though I've seen quite a few of those with the force 120hp.

I think you may need to go down to a 13p; if you do then get a 4-blade prop. The 4 blade design will help with the holeshot and cruise speeds. I wouldn't expect more than about 35mph with a 13p prop and that motor however.

Definitely get a tach installed. You need to know what RPM your running.

Cheers