496 exhaust overheat
 

Having problem ect overheat both sides sets alarm at 4000 rpm. Coolant temp ok and water pressure at 4psi ,alarm goes off and exhaust temp goes down 20 seconds after throttle is returned to 3500, coolant temp never changes, boat ran fine in fall when came out for winter, problem present when launched. Impeller changed did not make any difference any suggestions
Any help would be Greatly appreciated

Check and clean heat exchanger. How old are the manifolds. It might be time to take them off and see if there filled with junk. Either clean them out the best you can. As in tapping with a hammer and shaking them like a piggy bank to get it out or buy new. Risers could be full also. But easy to clean and don't go bad often.

First and foremost ECT is engine coolant temp not exhaust overheat ==== EMCT is exhaust manifold coolant temp.

with that said as I believe you met EMCT overheat for both sides

restrictions

heat exchanger end cap gaskets need to be changed every 5 years

check valves / check balls how ever one wants to call them

during the scan what is the temp readings for EMCT and with a

hand held temp gun

Thanks for the input, it is emct p&s reading with computer double checked with heat gun readings correct . heat exchanger clean , pulling boat to check intake elbow on transom.
Question water pressure reading does not go over 4 psi I would think if there is a restriction after pump that would rise with rpm? Just thinking it is a restriction before pump.

If you have a Baja with the factory fresh water flush fitting, pull that whole setup apart, and remove the check-ball from the Tee in that system. It's a POS, and you do not need a check-ball in there.

but he reports his ect is normal temps readings - water pressure and anything that is not exhaust manifold and or before the manifolds related for cooling would not report ect nromal temps. you can test your water pressure with a mech gauge.

With that said is your ect temps on the scan are normal on the scan thru out all rpms ? I can careless what the gauge reads for temps. Some of them can be way off. I have many off up to 15 degrees both ways

ect = engine coolant temps

crownline single engine all readings with computer and verified with heat gun both are pretty close changed pressure sensor it was off Now water pressure at is around 2.5 at idle At 3500 goes up to 4 at 4000 goes in guardian mode emct overheat runs 3500 all day engine temp never goes up.

It sounds like you have a blockage somewhere. How is the water flow out of the exhaust tips? Or do you have only through prop exhaust?

remove wps from its location then reconnect it with its connector -- then hook a mech psi gauge into that wps location to see if the psi reading is the same as the past scan tool readings while running the engine at the same rpms..

Impeller housing condition ?? fitting for water inlet inner transom assembly condition ? belt good and tightness correct ? heat exchanger restrictions ? location of wps ? back side of engine on the pwr steering cooler or water pump housing area ? year / engine serial number dictated the locations of the water pressure sensor = wps.

even a restriction way after the wps slows water flow dowe and then psi is lowered because of that. end cap gaskets for the heat exchanger are a huge problem and make the exhaust system run hot. They are maintenance item regardless.

where did you buy the wps from ? just an fyi the ones on ebay for cheap do not last so far 0 for 3 --- I have seen in person from boat owners whom bought from ebay and one out of the box did not work at all from another boat owner.

You mentioned an impeller change. Was pump assy changed or impeller changed in original housing?

Thanks for the suggestions working on it today. only merc parts used . curious about end cap gaskets they were sealing but deformed What is the huge problem?

You wouldn't think it would cause a problem, but BUP fixes these for a living, then comes on here and diagnoses problems for free. I haven't seen him wrong yet.

The deformations can block the tubes which are imperative to your cooling.

Thanks for the good words about me.

The jist -- the heat exchanger end cap gaskets not only deform they grow bigger in which blocks the water hoses connection outlets from the heat exchanger to the exhaust manifolds -- If you pull those hoses off from the heat exchanger - water will drain - then stick your finger up in there if you feel any rubber, your end cap gaskets are blocking the water flow to the manifolds. Also these are maintenance items of 5 year - then change out with new gaskets.. I am telling you as they should be changed regardless every 5 years or less or if you over heat the engine. Those gaskets are week - the end cap gaskets.

Any cooling water that can back up --- causes the water pressure to drop. Not saying this is your exact problem for low water pressure and those readings --- but I would NOT RULE IT OUT EITHER.

A lot of times the WPS itself, the hole has a bunch of junk in it or the WPS goes bad or restrictions to impede water flow or the impeller is weak or the impeller and impeller housing is the issue. GEN VII water pump housings are NOT that good for lasting - they scar very easily. This causes low water pressure as well.

Thanks to all. 'Fixed'' main problem was intake hose where it goes through transom. Corrosion around outside of hose crushed the retaining nut in the center of hose. I could not get a pencil through the opening. also changed end cap gaskets on heat exchanger.

496 brass gen 7 water pump. gre 7 repair kit for badly damaged pump body. If your brass body is badly grouved and fails to pump. our kit makes pumps work again without buying new pump. Rubber Impellers W/P Mercruiser Impeller Repair Kit $24.95. IMPEL

bottom of page,,works great