120 mercruiser overheating but oil stays cool to touch

[biggizmo]

bought a 1970 16' Larson with 120 Mercruiser marine #3849449. Put muffs on it & it ran fine. Water & exhaust flowed out of outdrive as expected. ran for about 10 minutes no problem. Put it in the water warming up at dock, took it out short distance & overheated. Oil pressure gauge indicates no pressure, and the oil was cool to the touch. However, intake hoses felt pliable but very hot. Also, tried to get it up on plane & engine shook violently. What's going on? Anybody help me out? Thanks!

 

[Scott Danforth]

Did you replace the impeller when you bought it? if not, my fist suggestion with a new to you I/O is to change the impeller. since you have overheated, I would suggest a complete waterpump kit with new upper and lower halves vs just an impeller.

the no oil pressure is another item you have to look into. could be something minor such as a bad gauge, or something serious such as you have no oil pressure and your motor is eating itself alive.

prior to spending any money on the water pump, pull the drive off. put a hose in the water inlet port on the transom shield and fire up the motor with a mechanical test gauge installed in the oil pressure galley.

if you have zero oil pressure on a mechanical gauge, you will be tearing the motor out anyway.

if you have oil pressure, then proceed on to replacing the raw water pump in the lower.

 

[biggizmo]

thank you for your input. I[m looking into all options & I am changing the impeller. You gave me the nudge & direction to get going on this...thanks!! Happy Boating!