Mercury 150hp (1989) issue/s

[eagle181]

This engine is on a 1992 Champion. It has a 15pitch prop (too small I know) and only runs WOT at 4800rpm at 3600ft elevation.

Issues:
- It is only pushing a 15pitch stainless Raptor prop at low RPM and low speed for the boat (40 half loaded/wot, 37 cruising)

Related issues possibly?
-In neutral will idle for about 3 minutes then die, while slowly trolling, (5-10mph) it will die after a minute or two. (giving more throttle just before engine dies only makes it die quicker both in gear and neutral.
-While attempting a 19pitch aluminium prop it needed to be nursed about half the time to get on plane...forward back forward back, etc.
-Sometimes it dies while in gear and attempting to get to plane.
Runs rough in neutral and low speed. Seems to run good on plane, 20mph or higher.

Thanks for any help,

 

[CharlieB]

Re: Mercury 150hp (1989) issue/s

First thing I recommended testing is fuel pump output, a weak pump or a poor fuel hose/connection allowing air to suck in will not keep the carbs filled and the motor simply runs out of fuel.

Disconnect the fuel hose after the fuel pump, point it into a suitable container and have a helper crank the motor while you watch the fuel stream. You are looking for a nice fat fuel stream pulsing out the diameter of the hose i.d. and at least an inch and a half long.

Replace that hose temporarily with a clear hose, pump the primer, rig the water hose flusher and start the motor. Watch that clear hose for any air bubbles passing thru indicating air sucking into the system anywhere before the fuel pump.

REMEMBER to REMOVE THAT CLEAR HOSE once finished with your testing and repairs, clear hose is NOT recommended nor approved for fuel use, only as a very short term testing tool.

Repost your progress.

 

[Chris1956]

Re: Mercury 150hp (1989) issue/s

How about a compression test and a spark test. Speed sounds too low.