When the engine has that problem, test the overheat sensor simply by disconnecting it momentarily to see if the problem is immediately corrected.... NOT to run the engine like that for any great length of time though. If that engine has the S.L.O.W. feature, that would explain it.

If no S.L.O.W. feature..... disregard.

I disconnected the wire from the sensor to the wire harness but I did not take the sensor out. It didn't change anything though. The engine has the slow feature but how it acts it doesn't seem like SLOW. In my manual it stated SLOW condition will limit the rpm below 3000 and stay constant. With my motor if I throttle up to let's say 4000 the rpm drops off completely and comes back up and back down until I throttle it back to below 3000. What kills me is it only happens sometimes, I may not see the issue again the next time I take it out.

1 - 1 & 2 - Yes, S.L.O.W. normally drops the engine to 2500 rpm and is a constant feature. Simply disconnecting the heat sensor as you did is a satisfactory test.

3 - If the change in rpms is a sharp instantaneous change, that would be ignition.... if a semi slow change of rpms, I'd suspect a fuel restriction.

If fuel, that could be attributed to a sticking Anti Siphon valve in the built in tank as follows:

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

NOTE: There has been cases when the output valve in the fuel primer bulb would come apart, and the inner portion of the valve would actually reverse itself and be drawn back into the primer bulb's output valve body. This in effect would create a shut off valve and result in a fuel restriction. If this is the case, you should be able to feel something laying in the bottom of the primer bulb when held horizontally.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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Check the compression and spark as follows.... what are the PSI readings of both cylinders? Is the spark as it should be?

(Spark Tester - Home Made)
(J. Reeves)

You can use a medium size philips screwdriver (#2 I believe) inserted into the spark plug boot spring connector, then hold the screwdriver shank approximately 7/16" away from the block to check the spark or build the following:

A spark tester can be made with a piece of 1x4 or 1x6, drive a few finishing nails through it, then bend the pointed ends at a right angle. You can then adjust the gap by simply twisting the nail(s). Solder a spark plug wire to one which you can connect to the spark plug boots, and a ground wire of some kind to the other to connect to the powerhead somewhere. Use small alligator clips on the other end of the wires to connect to ground and to the spark plug connector that exists inside of the rubber plug boot.

Using the above, one could easily build a spark tester whereas they could connect 2, 4, 6, or 8 cylinders all at one time. The ground nail being straight up, the others being bent, aimed at the ground nail. A typical 4 cylinder tester follows:

..........X1..........X2

.................X..(grd)

..........X3..........X4

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

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********************

I have brand new portable 6 gallon gas tanks with a brand new fuel line kit. Everything on the fuel side is new. The rpms do drop sharply not slowly. The only thing I've replaced on the ignition side is plugs wires and coil pack. The issue is very intermittent and when I don't have it the motor runs well.

I also just read about how the ignition system can be affected by the prop performance because of over/under speeding. This motor came off of a larger boat so could the prop be an intermittent issue like that? To me it seems if it were it would be a constant problem... I can't wait to buy a new boat! Lol I have never noticed a certain condition that causes it either. It is completely random. Al