MojoBoss

a FIY guy with a interesting temp issue. I purchased my boat new 2006 and My 496 starboard engine has always ran about 10+ degrees higher than my port engine - yes, this is not a show stopper by any means but, this year I had to replace my badly worn mercury raw water pumps with new pair of Hardin Marine Gen 7's and now this is the time to correct my temp issue (Wrenching on my boat today missing out on the Jax River Rally ). All throughout the yearly services I dove deeper in flushing, heat exchanger cleaning, T-valve, drain valve checks, replaced a kinked raw water line and no change in temps. On my starboard engine water exits the starboard exhaust more heavy than the port exhaust water is what I have observed so far.
I am able to restrict water flow out of the heat exchanger to the starboard manifold only then it evens out with heavy water flow out both exhaust pipes.
Is it possible that my power steering cooling is choking flow on the port exhaust (power steering has been flushed and does not seem restricted but, that is the only added hardware differences between the engines raw water systems)?
Any suggestions would be greatly appreciated?

SDFever

The water coming out of the tail pipes will almost always be a little more on the starboard side of the engine. It's because they both come from the heat exchanger but the port side tail pipe is fed more from pressure and the star side is fed from easier flow path. Running in the water it will even out more. On the hose you will see it often. The heat exchanger has to be completely full and pressurized with a volume of water that is hard to duplicate on the hose. As long neither side gets much above 160 when running you're fine.

Also if you measure or put your hand on it, the port side manifold and riser will often feel hotter than the opposite side due to same thing.

Regarding the 10 degree difference between engines? It's almost not worth talking about. How did you verify? Helm gauge, temp gun? Are you talking digital senders or analog? Underway at cruise or faster the coolant temp should stay right around 150 -160. It's normal for it to climb a little after hard run when slowing down but it drops after couple minutes.

MojoBoss

Using diag computer hooked up to PCM monitoring temps underway and at idle a 8 degree split which agree with console gauge temperatures running 159/160 degrees on port and 166/167 starboard engine.
Only real issue with temp split is when my raw water pump impeller gets worn the starboard engine temp alarm sounds off just when the adrenaline starts to flow - like this season when I pulled the boat for servicing only to find my raw water pumps housing with ware groves (new impellers didn't provide enough pressure) but, my new pumps got pressure!

gotstreetracin

could be just the sending units on the motors or maybe one isn't getting a good ground on sensor or something

NightHawk

My 2004 496 is the same way. Visibly less flow from the port manifold while on the hose and a 9 to 11 degree higher temp on the port manifold on the scan tool, both on the hose and underway at WOT. 120 vs 110 degrees at WOT. Running a new Hardin SS seawater pump. I stopped being concerned about it.

Bill 3

I have the same issue with my stbd engine running hotter than the port, it's always been this way, including he oil temps. I have traded out the guages and senders and the results are the same. I asked about it a long time ago with no answers. I got tired of chasing it and just keep an eye on my temps. The only thing I can think of is the power steering. Is it possible that the power steering would create that much heat to effect that much? I do know that the power steering cooler is the first thing the raw water goes through, then the oil cooler, then the heat exchanger....

I guess I could plumb in the power steering to run on the other engine and see what happens.
Bill

dereknkathy

try bypassing power steering cooler for a short run. easier than running 6 feet of hose to other motor.