98 johnson 150 oceanrunner

[kwt600]

would the idle adjust screws have anything to do with max rpms im only getting 4600 wot with new plugs, wires, power pack, fuel pump, fuel lines from tank to motor, carb rebuild on all 6, compression is good,all 110-105. running a 19 pitch prop. motor on 20' dual console trophy. we are lost any help is appreciated, thanks in advance

 

[Chris1956]

Re: 98 johnson 150 oceanrunner

Idle mixture adjustment only affects the idle. I have the same motor on my 21" dual console and run a 17" Johnson aluminum prop. I get a little higher RPM than you, but no more than 5200. It therefore sounds like your prop pitch it too great.

You might check to see if the motor is mounted low on the transom. I plan to raise my motor up an inch or so, and see if I can swing the 19" pitch prop.

 

[kwt600]

Re: 98 johnson 150 oceanrunner

that sounds like an easy enough fix. i have had guys tell me that i can "re pitch" my prop instead of spending 500$ on new one. my motor is a left hand rotation, and they are only availible in SS, how much of an rpm gain are we looking at if i drop to 17 pitch

 

[HighTrim]

Re: 98 johnson 150 oceanrunner

might want to try the prop forum.

 

[Chris1956]

Re: 98 johnson 150 oceanrunner

You should gain about 400RPM by dropping pitch by 2"

 

[Dhadley]

Re: 98 johnson 150 oceanrunner

Did you ever get more than 4600 rpm?

 

[kwt600]

Re: 98 johnson 150 oceanrunner

no that was the highest rpms reached since we bought the boat, 1st day we ran on water i got 4500rpms, ran great smooth idle, smooth throughout all 4500 just not enough. then the second time we ran the boat all the problems started. had to pump primer ball at higher rpms or it would slowly lose prime, so we replaced fuel pump, converted vro to straight pre mix. that fixed the surging and loss of prime. still we lost more rpms now down to 3800-4000. took to "master mech" in lewes de that cost 500$, he said it was power pack. that did absolutely nothing. then we replaced plugs and wires, that is where were at now, the plugs and wires took rpms from 4000 to 4600 i dont know what else to try. Im about ready for different color motor. hahaha one more question, would carb float height affect my rpms

 

[kwt600]

Re: 98 johnson 150 oceanrunner

bump???

 

[kwt600]

Re: 98 johnson 150 oceanrunner

does anybody have any ideas on wich way to go fuel? spark? timing? Im all out of ideas

 

[kwt600]

Re: 98 johnson 150 oceanrunner

anyone have any suggestions???? i need to get on the water. please help

 

[Walker]

Re: 98 johnson 150 oceanrunner

The first time you ran it you got 4500rpm's and it ran great, smooth idle. Now your getting 4600rpm's. I'd say you have too much prop.

 

[Dhadley]

Re: 98 johnson 150 oceanrunner

The first thing to do is run it with a test wheel. If it reaches full rpm then you know the motor is healthy and you can look at props or the hull or look for water trapped in the hull etc. Right now you don't know if it really is a motor problem or not. Your 500.00 parts changer guy should help you with that. You need to get something for the $$$.

 

[kwt600]

Re: 98 johnson 150 oceanrunner

I found another problem that might contribute to my low rpms.. port side butterfly valves are not matching up with the starboard side there is almost 1/4 inch difference.. so my question is could thisbe some of my problem, and if so how do i adjust???

 

[Gary H NC]

Re: 98 johnson 150 oceanrunner

If those carbs are not opening all the way sure that could be a problem.
Need to have a link and sync done to it...

 

[kwt600]

Re: 98 johnson 150 oceanrunner

alright so heres a new one did a de-carb on pistons and fuel system tonight, pulled plugs after, port side plugs looked like new and the other 3 they should, all black and soot covered anyone now if this is normal, or what could cause this new found problem. and i did check spark after i pulled all 6, and all 6 good strong spark???????????

 

[kwt600]

Re: 98 johnson 150 oceanrunner

anyone have any ideas?????????