Is the oil pump failing on my 89 merc 110hp?

[danpcro]

My 89 Merc 100hp outboard is overheating at low rpms only after about 15 minutes of use. I have checked the poppet valve, thermostat, and water pump and everything looks to be in good condition. Could this overheating be caused by an oil injection pump beginning to fail?

 

[shipoffools]

Re: Is the oil pump failing on my 89 merc 110hp?

If you are not sure aboout the oil injection pre mix fuel at 50:1 That may answer your question and will definately save your motor if there is a problem with the oil pump

 

[WillyBWright]

Re: Is the oil pump failing on my 89 merc 110hp?

Even if the oil pump were failing, the water pump should provide plenty of water to keep the motor running cool until the motor locks-up from lack of lubrication. Other possibilities you may want to look into is scale build-up on the cooling surfaces that will insulate the aluminum from adequate heat transfer. Sometimes the ignition system produces enough radio frequency interference to confuse the electronic warning module to produce a false signal, try supressor sparkplugs. When warning modules fail, they are designed to sound the alarm horn. You could have a bad overheat sensor.

 

[emckelvy]

Re: Is the oil pump failing on my 89 merc 110hp?

To take WBW's thread further, how are you determining the overheat condition? By the fact that the alarm goes off or are you also feeling the motor to tell that it's hot?<br /><br />If you feel the exhaust manifold cover and it's cool, or no more than lukewarm to the touch, the motor is not overheating. The head and block will be rather warm to the touch, but not so warm that you can't hold you hand on it for a few seconds.<br /><br />Are you sure the correct temp thermostat is installed? Some motors have the possibility of having a 120 deg or 140 deg 'stat fit and someone could have put the wrong one in. <br /><br />You say you checked the 'stat and poppet, but if you put the old ones back in they should instead be Replaced.<br /><br />Also, it's not uncommon to see the alarm module go bad and give false alarms, so that's another possibility if you determine there is no overheat condition.<br /><br />BTW, I understand that Radio Shack sells an infrared thermometer, which could be very useful in determining operating temps.<br /><br />HTH and let us know what you find............ed

 

[danpcro]

Re: Is the oil pump failing on my 89 merc 110hp?

I replaced thermostat and water pump and used my boat briefly with no problems. I am going to have to wait till next spring for a full check of the engine. I would think that if the oil pump where failing the extra friction would overheat the engine regardless of the water flow but I would obviously hate for this prediction to be wrong. Is there sure way to know if an oil injection pump is delivering the proper amount of oil? Thanks for the advice.

 

[Clams Canino]

Re: Is the oil pump failing on my 89 merc 110hp?

The easiest way to tell for sure is to drive the boat and measure the consumed gas/oil ratio. Add some 2cycle oil (50/1) to the gas if your nervous doing this test.<br /><br />-W

 

[robbyusa]

Re: Is the oil pump failing on my 89 merc 110hp?

Run 50:1 mix for 6 gallons your oil resivoir level should drop close to 1 pint of oil if you run mostly on plane or higher RPM's for the entire tank.