Constant alaram on a 95 johnson 2

[Overexposed]

Hope yall can help have been chasing my tail on this one.
I have a 95 johnson 225 and recently its been sounding its constant alarm when you get on plane and put the throttle down. So i looked it up in the service manual and it says that alarm is over heating, so I go threw and replace the 2 thermostats and throw a new water pump on with the new housing and wear plate and so forth. Doesn't fix the issue had 10 pounds at idle and while underway has 30 pounds so its not water flow (unless there is a blockage somewhere). so I threw a new VRO pump on had a new one as a back up just incase. wasn't that.... I took it out and when the alarm goes off its a constant alarm when your getting into the throttle but as soon as you pull out it goes off that was happening at about 4000 RPM then I ran it at 3xxx rpm for a while and it started to sound the alarm off at that speed also and so on as I kept running it started going off at slower RPM.
Any advide would be greatly apricated!!!

Thanks , Jeff

 

[Joe Reeves]

On that model (and many others) the constant alarm will sound via a Overheat problem" and also a "Fuel Restriction" problem. However, a fuel restriction problem usually results in the fuel primer bulb having a tendency to flatten out somewhat and the engine to have a drop in power & rpm... two things that would get your attention of which you do not mention. A fuel restriction is normally caused by a sticking Anti Siphon Valve (as follows).
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(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.
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Also, pertaining to a "Overheat" scenario which may be flawed..... Perhaps one of the overheat sensors in the cylinder heads has failed, causing the warning horn to sound at a lower temperature.

This test is a touchy one so be sure that the removal of these wires in a very short momentarily one!

Temporarily disconnect the heat warning sensors when this problem occurs. If this causes the problem to cease, reconnect the wires immediately, then plan on replacing that failing sensor ASAP.
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One other cause that I've encountered is that, if using the regular OMC type control box, is that as the throttle handle is advanced, a inner portion of it would slide against the terminal of the horn containing the TAN sensor wire... and that effectively would complete the circuit to have the horn sound off. Yeah, that'll drive'ya nuts!

 

[Overexposed]

Thanks for the help I put a new primer bulb on seemed to help but then continued to go off at higher rpm, so I figured that helped took the anti siphon nipple off and that was clear so pulled the hoes off the in hull tank and stuck it in a 5 gallon gas tank and went out and ran it no problems like that. So im assuming the pick up is messed up and or junk in the tank or pick up so i will pull apart and let yall know as soon as possible what I figure out