RPM Problem

Status
Not open for further replies.
B

Bob Fischer

I've been having problems reaching the max rpm while in gear for 2 seasons now. I have a 1985 Universal M18, (14hp). It should reach 3200 rpm, but it only reaches 2200. In neutral it reaches the required wide open throttle rpm. The tach is good, I replaced the injectors last winter, the prop is stamped with its pitch and diameter, which are whats called for for this boat. I can only make 4 knots under power, and thats without wind or current. Any suggestions would be appreciated.
 
R

Randy

Not reaching full RPM

I'm no expert but a couple of possibilities come to mind: Not enough air--is your intake manifold or air intake blocked? Perhaps the air filter is dirty. Too little air will produce black smoke under heavy load. Not enough fuel--are your fuel filters dirty, allowing enough fuel for full rpms in neutral (no load) but not enough in gear (full load)? Barnacles on the prop, or a line wrapped around it. Prop shaft bound up by stuffing box, etc. Does the prop shaft turn freely by hand when in neutral? Is the hull bottom clean and smooth? Lack of compression--serious engine wear might mean the engine doesn't generate enough compression. One last thought: are you sure the tach is accurate? Last time I had an rpm problem, I was ready to start making repairs to the engine, only to find that the tach was incorrectly adjusted. Good luck in tracking down your problem. Randy
 
Status
Not open for further replies.