90 Yammy that false alarms

[Polecat]

This one has beaten me. I need help. I have a 1999 Yamaha 90 (2 stroke) that is very low hours and has been well-maintained. A couple months ago it developed a problem that I have not been able to diagnose. I'm hopeful that somebody out there has run across this one and can help. The symptoms- The motor runs fine for approx 20-30 mins on the lake and then the overheat alarm sounds. What's interesting is that the water stream coming out of the engine is cool, and there's plenty of water coming out. What's really odd is when the alarm sounds I can make it stop by adjusting the tilt/trim (in any direction), from my throttle control lever. I hear the alarm, I move the tilt/trim adjustment and the alarm goes off. It will eventually alarm again, sometimes right away, sometimes not for several minutes, and I again have to adjust tilt/trim to make it stop. I don't have to change throttle speed, simply tweek the trim adjustment. So to use the boat I have to continually change tilt/trim or the alarm continues. If I don't adjust the tilt the motor will reduce to idle speed. When this happens I put the throttle back in the neutral position and then I can immediately accelerate again w/ no alarm. The fact that I can do it immediately is probably an indication that the engine is not overheating. Couple that with the fact the alarm stops if I move the tilt/trim probably also means that there's not temperature or oil issue. The motor is using plenty of oil. I'm totally stumped. If the alarm sounded and stayed on it would make more sense to me, and would be easier to trouble-shoot. Sometimes the alarm won't come back on for a very long time, and sometimes it will come back on within seconds until I adjust tilt trim again. And it matters not what temperature the air and water are when it happens. I've been fishing on 40 degree F. days w/ the water at the same temperature and the symptoms continue HELP!

 

[rodbolt]

Re: 90 Yammy that false alarms

are you sure its overheat? its possible the alarm pink wire is grounding at the cable entry point or in the cowl.<br /> its also possible the temp switch is failing

 

[Ray Neudecker]

Re: 90 Yammy that false alarms

The description of the problem and cure would have me looking for a wire pinched around the cowling entrance also.

 

[Polecat]

Re: 90 Yammy that false alarms

Originally posted by rodbolt:<br /> are you sure its overheat? its possible the alarm pink wire is grounding at the cable entry point or in the cowl.<br /> its also possible the temp switch is failing

thx to both Rodbolt and Ray for such fast replies. I'll check the pink wire path this coming weekend to be sure that it's not grounding anywhere. 2 related questions:<br />1. is there only 1 pink wire, and is it easy to locate (where should I look first)? <br />2. where exactly is the temp sensors? I didn't see anything externally that looked obvious.

 

[Ray Neudecker]

Re: 90 Yammy that false alarms

The temp sensor will be located in the head. It will have a pink and a black wire attached.

 

[Polecat]

Re: 90 Yammy that false alarms

Originally posted by Ray Neudecker:<br /> The temp sensor will be located in the head. It will have a pink and a black wire attached.

 

[Polecat]

Re: 90 Yammy that false alarms

thanks again Ray. I'll diagnose the problem by first trying to find a pink wire that's somehow grounding itself, and if I find nothing I'll attempt to look at sensors, however I'm unclear why a sensor would reset when I adjust the engine tilt/trim. I was thinking that disconnecting both the oil and heat sensors and running the engine to see if the alarm comes on. If it still does, then I'm really stumped (unless again the pink wire is finding a ground someplace). Another thought- is it possible that the problem is not on the engine, but instead at the control lever (or on the alarm speaker itself?)

 

[PDwhaler]

Re: 90 Yammy that false alarms

I am going thru a similar problem. I have a 2001 90 Yam on a 17 whaler. When going thru turbulent waters, sometimes I experience a loss of power where the engine cuts out down to idle speed. I then back the remote to neutral and can accelerate right back up again. I have an oil injection tank under the cowling. I strongly suspect the sensors in the oil tank are shaken to the point where it sends a false reading to the main computor that the oil is running out and treats it as an over temp condition. Remember, there is another sensor at the thermostat which is the true indicator of an overtemp situation but the sensor in the oil tank that indicates low oil shuts the engine down in the same manner. Also, the yamaha makers force you to go back to neutral because, in a low oil situation, they don't want you to fill the oil tank back up and have the boat take off on you and out you in danger. Anyway, I am now looking into replacing the sensor in my oil tank. I'll let you know how I make out.