120 hp late 80's Johnson

[a 5 basslimit]

A friend of mine has just purchased his first bass boat and he is noticing that the motor has a hiccup or kick when its running at medium or fast speeds. It currently idles fine. Could this be bad gas? Carbon build up? Any thoughts?

[sc419795]

I am by no means an expert...and the guru's will be around shortly. Will go a long way if you include Model and Serial of the engine. I also suspect they will tell you to do a compression check and clean the carbs. Good luck!

[noelm]

do the easy non invasive things first, before you go pulling things to bits, change the plugs, have a look at them, are they all the same? or is one black, white, brown? do a compression test while they are out, can you try a complete new tank, hose and fuel? the chances of it being compression or fuel is remote (though possible) but you need to eliminate those first. Next, do you have a genuine manual? if not, get one.

[a 5 basslimit]

Where would the model/serial # be stamped at? On my yamaha its on the motor bracket that bolts to the transom...... We pulled the plugs and they all look good. would the wrong plug cause this?

[noelm]

numbers should be in a similar place, on a small plate riveted to the bracket, incorrect plugs could cause a problem, (maybe) are they the wrong ones?

[craigs06]

Sounds like a carb kit is in his future. Carb motors, especially after sitting up for a while, are notorious for carb issues. Floats sticking, gaskets leaking, etc. What you describe is floats. If it is stuck letting too much fuel in, it will wash down the cylinders and hurt the motor; washes the lubrication out. If they are stuck not letting enough fuel in, you will lean it out followed shortly by a melted piston. Either way, doing nothing is not good. Cheap and easy to install carb kits, I think I would go that route to eliminate that concern. If you still have the problem, look for electrical.

In order;
compression check
Fresh gas
new plugs
carb rebuild
electrical system

[a 5 basslimit]

ok sounds good thanks for the help guys much apprecited.