More power

[bonehead28]

I have a 1980 85hp johnson and would like to up the proformance a little bit i have a 23 pitch prop but heard there was little things you can do to the power head and gain 5-10 mph any ideas.

 

[Dhadley]

Re: More power

Welcome!<br /><br />Performance is like taking a trip. We need a map. We need to know where we are now and where we want to go. Then we can tell how to get there.<br /><br />First, "up the performance little bit" and "5-10 mph" rarely go together unless your present set up is horrible.<br /><br />Tell us more about what your rig is doing now and what you would like it to do. Skiing, strictly top speed, holeshot etc. Whats the top rpm with an average load? What hull? <br /><br />A 23" prop on an 85 indicates you have a very light performance type hull. Cool. Tell us more about it.

 

[DJ]

Re: More power

I'm with Dhadley. A 23" prop on an 85 must be (I hope) on a really light hull. Tell us more.

 

[bonehead28]

Re: More power

its a tri hull its runs about 40 mph would like 45-50 if possible with out much money.im really after more more top end

 

[jimmbo]

Re: More power

What lenth of tri hull? What make and Model would be helpful. 40 mph out of an 85 isn't too bad. What rpm are you running at wide open? Speed costs money.

 

[bonehead28]

Re: More power

it's a 79 model 16ft trihull 4800rpm

 

[Dhadley]

Re: More power

I take it the motor is mounted all the way down on the transom?<br /><br />The first thing is to do a compression test so we can verify the health of the ponies.

 

[bonehead28]

Re: More power

yes motor all the way down.130psi across the board on compression

 

[Solittle]

Re: More power

We should be able to get you a couple of that 10-15 mph. First you need to get your motor mounted in the right place on the transom. Ususlly this is with the cavitation plate being even with the bottom of the hull or around 1" above the bottom. This will get you the minimum drag.<br /><br />Next you need to get your motor spinning at the right rpm by having the right pitch prop. For your motor this should be around 5500 rpm. I would adjust the height of the motor first then see what the max rpm is. I would suspect that it will be more than 4800 rpm. Then go for the prop. My guess is that you will wind up getting either a 19 or 17" pitch. This will improve both hole shot, top end and help keep the motor from lugging.<br /><br />Most folks, I think, will advise you to get a biggger motor if the above does not satisfy your need for speed.