Islander

I own a 01 fountain 35 X with twin 496 HO
I have been trying to isolate an overheating problem with my 496 w/200 hrs. The troubleshooting and work performed so far is , inspected and replaced sea pump impeller, cleaned and inspected main heat exchanger, removed and cleaned oil cooler. My pressure at idle is 16lbs whereas the starboard motor is around 6 lbs. I am at the point where I pulled the intake hose off the oilcooler and ran the motor and still got the 16lbs reading, which would indicate to me the blockage is b/t the pump and the oil cooler, I then pulled the hose that connects to the pump and did a volume test and got considerably more water flow compared to the flow at the oil cooler. This is puzzling to me because I not aware of any restrictions b/t the pump and the oil cooler. Does anyone have any advice on my problem?
Thanks in advance

Raylar

How and when is the motor overheating? The raw water pump is on the lower right front of the engine and the oil cooler is over on the lower left rear of the motor. I believe the water leaves the pump goes back to the rear of the motor and up to the power steering cooler and then down to the lower left of the motor where it enters the oil cooler. check on your motor, it sound like you may have some blockage at the power steering cooler on the top rear of the motor. It is also not uncommon for the 496's to have different water pressures , motor to motor and both your pressures are somewhat within the normal range with the boat in the water. Your problem may be somewhere else such as a thermostat sticking or raw water exiting the motor at the exhaust system.

Just some thoughts,

Regards,
Ray @ Raylar

Islander

It will overheat if I run over 3k rpm and I think the sensor is on the manifold. The exhaust manifolds are much hotter than the other motor. The problem motor at 2800 rpm will run around 175f and the other at the same rpm is around 158f. If there is another intercooler b/f the oil cooler then that could be my issue, its not easily seen on the fountain, funny I was told by my dealer and merc down at miami boat show that the oil cooler would be the first obstruction. I do think it is b/f the oil cooler just because when I pulled the hose off the raw water pump I got a much higher volume of water flow then came out of the hose at the oil cooler intake; almost twice as much. fyi I was testing in water not off a hose.

thanks

carrboy

Pull the ends and hoses off the cooler on the back of the motor.Make sure water is flowing through there good.I sucked up some sand and plugged mine right up before.It was a long time ago but I think I had to replace the impeller twice.I think it ruined it again after I replaced it cause the cooler was still plugged.

Raylar

There is definitly a power steering cooler on the engine and its usually on the back of the motor on top of the Bravo bellhousing just behind the engine block. It also usually has the water pressure sensor threaded into one end closest the inlet side. I suspect this might be were the obstruction is, possibly old pieces of an impellor or something that got sucked in and ran thru the raw water pump. good Luck, let us know what you find.

regards,
Ray @ Raylar

LAKESIDE RESTORATIONS

You may have sand or sediment in your heat exhchanger. They should be periodically flushed/cleaned.. Jamie / Lakeside