200 Merc overheating, erratic water psi, prop & poppet questions

[sbklf]

I have an overheating issue with my 98 Merc carbureted V200 S/N OG752293 outboard. While running close to WOT, the RPM increased and shortly afterwards (20 seconds) it overheated. The motor was jacked and trimmed up a little higher than normal so thought that was the problem. Now it seems to maintain good water pressure & run normal temp at mid throttle but when close to WOT, at times, I get the RPM increase again and then notice erratic water pressures (literally bouncing between 0 and 20psi) and overheating. Running in a tank, the water pressure at idle is good (2-5 psi) and the head temps are good (150F). The water pump, poppet and t-stats were replaced last year and we ran with no problems till now.

-My prop guy had to put some cup in the prop and advised it is pretty worn. Can a prop issue create a cavitation condition and cause the water pump to lose prime?
-What are the symptoms of poppet issues?
-Can poppet issues cause erratic water pressure?

 

[wired247]

Re: 200 Merc overheating, erratic water psi, prop & poppet questions

If you are ventilating the prop and your RPM rises you could be getting air into the water intakes as well. The prop slipping is a symptom of running it to high as is the water pressure jumping around. Mercury makes a clamp on device that scoops water in from the front of the water intakes that helps or you can install a low water pickup and use a prop more suited to surfacing. Or you could just lower the motor.

 

[sbklf]

Re: 200 Merc overheating, erratic water psi, prop & poppet questions

If you are ventilating the prop and your RPM rises you could be getting air into the water intakes as well. The prop slipping is a symptom of running it to high as is the water pressure jumping around. Mercury makes a clamp on device that scoops water in from the front of the water intakes that helps or you can install a low water pickup and use a prop more suited to surfacing. Or you could just lower the motor.

So is prop ventilation due to a worn prop? If so it seems rebuilding the prop should correct it. I don't think I need a low water pickup but am interested in the scoop you speak of, can you give me more information on that please? I think we have the same motor (from your picture).

Thanks for the reply, Kevin

 

[wired247]

Re: 200 Merc overheating, erratic water psi, prop & poppet questions

The prop ventilation is just from having the motor mounted too high for that type of prop. Some props run fine mounted high and some don't. If it sucks air it ventilates and spins up . Could be caused by the same thing that is causing you to overheat. The motor is possibly mounted too high and air gets into the side water intakes.

 

[Dukedog]

Re: 200 Merc overheating, erratic water psi, prop & poppet questions

Over trimming or motor is to high. Bouncy water pressure indicates ya suckin' air...............

 

[Faztbullet]

Re: 200 Merc overheating, erratic water psi, prop & poppet questions

+1 on Dogs reply...drop jackplate 1/2 inch and retest.