1992 Mercury 150 Warning Horn

[c_mcfarland]

I recently purchased a 1992 Robalo with twin 150HP Mercury Outboards. Occassionally when taking the boat out and giving it a little extra gas, one of the warning horns goes off with an uninterrupted beep. I come to a stop and shut down the engine producing the warning sound. After waiting a minute and then restarting the engine, the warning sound goes away and typically will not return unless I really step on the gas. I have checked the oil resevoir and there appears to be plenty of oil. Does anyone have any suggestions as to what might be occurring and how I might address the issue? Thanks in advance for any help you may be able to provide.

[KennyKenCan]

If it is a continuous alarm, you are overheating!You must look into this problem immediatly or you may face costly repairs!Further diagnosis is required.Kenny

[c_mcfarland]

Do you happen to have any suggestions as to what steps I might be able to take to attempt to trouble shoot myself if possible before I have to call in a mechanic? Thanks again for any assistance you may be able to provide.

[Blindo the Frog]

Not that Im anything close to an expert on these matters but a "continuous steady beep" is indicative of overheating rather than lack of oil. You could try checking the tell-tale at high speed (but only as long as someone else is driving the boat!!!!!! ) and see if it is any different ie. non-existent, spluttered, intermittent.

[CU2NITE]

First you should get a manual, clymer sells a good one, and read up on the motor. DOn't you have a temp. gage on the boat? I think the horn sound around 210F. If you are overheating I would first pull the lower unit and check impeller and houseing and go from there. If your starting your motor out of the water you probably have fried the impeller. If you don't know how to do this get that manual and it will guide you through. It helps to have someone with you to pull and put the lower unit back on. Good luck.CU

[robalofish]

If you have recently acquired this boat see if you can get some history on the engines – When were the impellers last changed, has it had new thermostats, plugs, lower unit oil etc.If you are unable to get this info I would suggest you give yourself some sort of starting point. All of these need some sort of basis for future maintenance. You should do all of the above on both engines ASAP.You currently have an overheating condition based on the alarm. I would start by changing the impeller and the thermostats first. I also would do it on both engines.Good idea to have 2 manuels 1 from merc and one "other". Sometimes if one is not clear the other will have more details.Good Luck - Robalo is a great boat. I've got a 2120cc.RFish

[ignatz]

I just went through this with my 1994 Robalo with twin 150s. The alarm does not go off when the boat is idling or at slow speed. The alarm goes off when the boat is on a plane. My bet says it is your water pump. Replaced mine and everything is fine now. Don't push it or it will cost you big bucks !!!

[Omaggmm]

I had a similar problem on one of a pair of 200 Mercs. They always had plenty of oil in the resevoir, but one needed to be topped off. Perhaps 3/8" or so. That would stop it until next time out. I think that my problem was in the sensing switch in the cap. Good luck

[c_mcfarland]

I have had several suggestions that it may be related to the water pump on the motor in question. I went out and started the motor and once the engine is going, it appears that I am getting a steady tell tale out of this motor. Should I continue to assume that it is the water pump or could it be related to the thermostat or possibly something else? Again, thanks for all of the advice for I really appreciate it!

[NICK JONES]

It pays to change those water pumps (impellers) regularly as it's neither expensive or time consuming.If someone has started this motor out of water for only a few seconds then that's enough to damage the rubber impeller and cause an overheat situation. I think that the poppet valve on the starboard side of the motor can also become full of grit etc causing it to jam open and limit water pressure available for cooling. There is a cover plate you can remove to quickly check this, but either way make sure you fit a new impeller to each motor.