1996 Johnson 200 overheat alarm

[Tom McDonough]

Just had the impeller and both thermostats replaced last month after steady alarm at 4000rpm. First time out this past weekend, same alarm at 4000 then 3500 and by the time I got back to dock I had to run at 2800 to keep the alarm from sounding. Indicator stream is fine. Could the exhaust manifolds be corroded?

[seahorse5]

Change out the pressure relief valve as the new one has grooves in the bullet nose to bleed out any trapped air. Also replace the rubber seal and check the area for corrosion buildup.

Make sure the correct water pump was installed. If the 5001594 pump kit was installed and the motor requires the 5001595 kit, the motor will overheat. In addition, make sure the impeller orings are installed correctly and the air bleed groove is clear.

[Tom McDonough]

Thanks, I will mention these things to my mechanic.

[Dhadley]

If it didn't go into SLOW, it isn't overheating. Since the problem seems to be related to throttle position it's probably a fuel restriction alarm. If your mechanic doesn't know that, it's time to find another shop.

However, if you are telling the mechanic to "change this or that" he probably isn't looking for the cause. He's just doing what you requested.

[Tom McDonough]

When I had the pump and thermostats replaced (they were due) he also replaced the fuel/water separater and the inline fuel filter to rule out a fuel restriction as you say. The alarm was steady which i though indicated an overheat alarm.

[dajohnson53]

When I had the pump and thermostats replaced (they were due) he also replaced the fuel/water separater and the inline fuel filter to rule out a fuel restriction as you say. The alarm was steady which i though indicated an overheat alarm.

Steady alarm can mean two things: overheat or fuel restriction. The difference is that overheat also causes the engine to go into SLOW mode, dropping RPMs. Fuel restriction alarm doesn't drop RPMs - but is usually closely related to RPMs - alarm goes off at higher RPMs, but then goes away when RPMs are reduced by operator.

As for the cause, I don't have any idea, but I would be surprised if the mechanic doesn't realize that steady alarm without the SLOW mode kicking in would be fuel restriction. If I were troubleshooting something like that myself, I'd do what you've done so far (filters), but I'd also go all the way through the fuel supply from fuel pump (that's where the sensor is) to the pickup inside the fuel tank. Also, there could be debris in the fuel tank that intermittently clogs the pickup.

[Dhadley]

Also, there could be debris in the fuel tank that intermittently clogs the pickup.

And / or the anti-siphon valve. Or the vent may be partially plugged.