Help please; 120 hp Evinrude bogs down at 3k rpm

[labxxxbrat]

Boat has been behaving well except for misc. electrical issues (salt water). Boat runs great, 19.x ft center console sportsman with 120 hp, 2 stroke outboard. Had a new magnito replaced a few months back and everything has been running smooth. Coming back from the Gulf this evening and scooting around 4200 rpm, an alarm sounds. I look at everything and it appears fine however, the temperature begins to rise as does the battery charging meter. The charge meter is still in the green but is slightly above 14vdc. I understand that 120% charge rate (13.8 vdc) is normal and a little higher is tolerable. Now, the temp guage is starting to climb higher. I examine the water coming out of the engine (cooling); excellent. I pull over, turn off the engine and check the cover for excessive heat. Within tolerance/fine. Tilt the engine up, water comes out, tilt it back down, start the engine and everything is fine. Scoot for 10 minutes at 4000 rpm and the engine bogs down again. At this point, I disconnected the alarm and simply monitored the temp/charge meters. Temp normal but charge a little over 14 vdc. Pull over, stop engine, tilt engine up/down, restart. No problems, behavior is normal but now it bogs down if I go higher than 2800 rpm or so. The engine feels like it is misfiring and is awfully sluggish. I made it home but my boat is not happy. There were a couple of times that I could scoot around under 5000 rpm and have no problems and then there were times that I couldn't get it above 3000 rpm without it really shaking. Tilting the engine up/down intermittantly kept the voltage level within check... dropped down below 12v (still green) and slowly raised up to 13 and then quickly went up to 14+ vdc.
I am not sure if these are related problems as I always seem to have wiring issues with the salt water.
Any help would be greatly appreciated. The engine has been a great engine. Think it is a 1998 engine. Also, no smoke coming from the engine (except when I cold start it ... normal).

 

[emdsapmgr]

Re: Help please; 120 hp Evinrude bogs down at 3k rpm

Check your owner's manual, It is a newer engine and should have the SLOW system on engine. This protection system will limit the power pack rpm to 2500 to protect the engine from damage when it senses a fault. This is done by cutting out cylinder spark. You should get a horn first,for either an overheat or fuel pump problem-then it will go into SLOW mode until corrected or reset, (when you restart.)

 

[labxxxbrat]

Re: Help please; 120 hp Evinrude bogs down at 3k rpm

I screwed up; it is a 1992 Evinrude engine. Somehow, I thought it was 1998.

 

[ezeke]

Re: Help please; 120 hp Evinrude bogs down at 3k rpm

S.L.O.W. is standard on the 120 and 140 from 1988 on. The most likely cause of the problem is overheat though it could be the VRO2.

You may want to test your warning horn because it should have sounded an alarm.

 

[labxxxbrat]

Re: Help please; 120 hp Evinrude bogs down at 3k rpm

Thanks to all who have participated with my issue. I will look into all that was mentioned. As well, the horn/buzzer did sound and after quite a lengthy time frame, I disconnected it to subdue the noise.

Thanks again and I'll keep you posted as to my findings.

 

[labxxxbrat]

Re: Help please; 120 hp Evinrude bogs down at 3k rpm

Hello all! Here is the summary of fix;

Cleaned/examined the plugs: noted nothing particularly wrong.

Replaced the thermostats and took it for a test drive. Failed. Engine still overheated and went into SLOW mode.

Took off lower half and replaced entire water pump. Test drive revealed failure, same situation.

Took off the head covers and found that one of the cylinder heads had been "Steam cleaned" which meant that water was getting into the cylinder. I replaced the head gaskets on both head covers and took it for a test drive. Everything worked well and have since been out and about with absolutely no problems of overheating. In fact, the boat seems to be running smoother and stronger.

I hope this helps anyone with an Evinrude, 120 hp 2 stroke/4 cylinder engine (1992).

Again, thanks to all that have been of value in their support/advice!