1997 Johnson 150 Ocean Pro Idle amp Throttle Advance Problem

[Grover Sheldon]

" Just bought a used boat whic

" Just bought a used boat which ran fine for some months; however, recently when trolling or idling for any length of time the engine begins to run rough and the engine speed goes to 1500 to 2000 rpm. I have changed all plugs, new fuel filter, all new gas with injector cleaner, cleaned the injectors with cleaner at the solenoid port, cleaned the filter at the engine, and cleaned what I could of each intake bowl with carb cleaner, inspected all the fuel hoses for kinks and collapsing. Seems after I advance the throttle, the hesitation can go on for 4-5 minutes then the engine roars to life. Yesterday when this happened, I removed the motor cover and I could advance the throttle with good response by moving the throttle bar on the engine itself. This left me really puzzled. Could this be an electronic problem or spark advance problem? It is really frustrating since the problem does not happen all the time and did not happen when I took it to the local J-E shop. Your input would be greatly appreciated.
Thanks "

 

[joereeves]

"Grover.... I retired before t

"Grover.... I retired before that engine was put into production, so I can't comment on the actual mechanical aspects of the engine, however.....

Your explanation of the problem has all of the characteristics of a engine that has developed a lean running condition (not being supplied the proper amount of fuel).

If a fuel restriction existed, the warning horn should engage, and that hasn't happened. A fuel restriction also has a tendency to force the fuel primer bulb to collapse. (I'm assuming that your warning system does function.)

That leaves me with the thought that either a air leak exists in the fuel line somewhere, or that the fuel (gas) side of the pump is failing.

The above problem could be checked out by simply pumping the fuel primer bulb (acting as a manual fuel (gas) pump) to force fuel to the engine's carburetors. If that corrects the problem, it would lead you in the right direction to correct it.

If the primer bulb has a tendency to stay flat or spring back very slowly, that would indicate a fuel restriction. If this is the case, and you have had no warning (horn), find out why.

Joe

"

 

[Grover Sheldon]

" Pumping the primer bulb has

" Pumping the primer bulb has no effect on the acceleration problem and it does not collapse. I plan to replace the fuel lines and buld from the tank in case the are collapsing on the inside of the line (had that happen some years ago and a very good mechanic found the problem) The situation of advancing the throttle bar on the engine (not the throttle ifself) and getting instant acceleration has me stumped. If it was fuel starvation, then that should not happen. Btw, the warning horns work fine. Thanks for your reply as this is obviously very frustrating to me. "

 

[LI JOE]

I have a 1999 15o Johnson and

I have a 1999 15o Johnson and I bought it new with the exact same problem. Numerous trips back to the dealer proved to be useless. Eventually I solved the problem myself with nothing more than a screwdriver. All I did was increase the idle/slow speed rpm's two clicks up. The engines idles a bit faster when she is cold but once she is warm she slows down to normal.

I equate the problem with the fact that many omc dealers don't tune their engines hot and on the water with normal water pressure on the exchaust. A mechanics tub or pool does not have the same water pressure as millions of gallons of open water. The omc mechanics tend to tune these engines with the idle rpm's too low.

 

[LI JOE]

I have a 1999 150 Johnson and

I have a 1999 150 Johnson and I bought it new with the exact same problem. Numerous trips back to the dealer proved to be useless. Eventually I solved the problem myself with nothing more than a screwdriver. All I did was increase the idle/slow speed rpm's two clicks up. The engines idles a bit faster when she is cold but once she is warm she slows down to normal.

I equate the problem with the fact that many omc dealers don't tune their engines hot and on the water with normal water pressure on the exchaust. A mechanics tub or pool does not have the same water pressure as millions of gallons of open water. The omc mechanics tend to tune these engines with the idle rpm's too low.