96 150hp Johnson Powerband???

[sstaz]

Hello all, I have a friend with the above motor on 21ft Trophy. The engine acts like it has a powerband. As you are accelerating it will all of a sudden take off like you went to full throttle and when throttling down it will hit a point and drop off quick. It is not because the boat is planing, as you can get it to do it from a dead stop. I have checked the throttle linkage for sticking and it seems to be nice and smooth. It does appear to happen when the throttle just starts to turn the timing plate. I hope someone has an idea as it is kind of dangerous running in big waves like that.

 

[tashasdaddy]

Re: 96 150hp Johnson Powerband???

link n sinc.

 

[sstaz]

Re: 96 150hp Johnson Powerband???

I was thinking sych problem also but wanted to see if I was on the right track.

 

[Chris1956]

Re: 96 150hp Johnson Powerband???

does your speed increase. or just the RPM? Could be a ventilating prop

 

[sstaz]

Re: 96 150hp Johnson Powerband???

She takes off like a raped ape when it happens so I dont think it is a prop issue. I am probably going to start checking it tomorrow.

 

[Chris1956]

Re: 96 150hp Johnson Powerband???

OK, How about a cylinder not firing, and then it starts firing, giving the big power boost.

 

[sstaz]

Re: 96 150hp Johnson Powerband???

Ok, I really feel like a moron now. I was just talking to my buddy and he informed me it is a Merc:redface: Now I have to regain my composure and start over again.

I am still going to try the link and sync but maybe it will open another window. Chris, I dont think it is a missing problem as it really does run great other than that. If I try and hold it around 3500 RPM that seems to be the point of no return, she will either drop back to 3000 or jump to 4200 or so. There is no happy medium, and that poses the problem when running in big waves. She rides best between 3400 and 4000 going into 4+ footers on lake Erie, but i cant seem to hold it there I know it's not a plane issue because I deal with that on my boat and others trying to run slow