Re: M/C 470 Still Heating Up!
OK,
I have flushed every passage, tube, hose, heat exchanger etc and I have water circulating in all directions.
So, you?ve flushed...with what, a garden hose? Nowhere near the volume supplied by the impeller pump!! Too little volume, especially in the exhaust passages.
I did pull the ends off the heat exchanger.
....and did you find any debris on the inlet (fwd) tube sheet/ Were all the tubes clear of obstructions? Now you need to remove the riser and check for obstructions. Remove the exhaust elbow bellows and peer down into the exhaust elbow (where the shutter used to live!!)...examine for obstructions.
When my engine first got hot and I pulled the sterndrive off, I checked the exhaust passge as far as I could get my hand up it and found no debris.
...and did you look in BOTH directions...into the transom and down into the outdrive? Did you inspect the water supply hose from the drive to the transom nipple for kinks or other deformations?
When I took apart the lower unit to rebuild the water pump the plastic pipe was melted but the impeller was good.
...I find that kinda odd. If the water pump was failing/failed, I would expect apparent damage to the impeller and/or housing. Having you report just the plastic tube melted reinforces my opinion that the exhaust temperatures are too high resultant from insufficient cooling water.
I did not replace the plastic housing and I think herein lies my problem.
Well, me thinks ya? got that one right !!!!! ALWAYS replace the housing, impeller, plate and gaskets as cheap insurance.
After putting it all back together and running the engine in a drum and with muffs it still over heated.
I can?t quite see your rationale for both the drum AND muffs. Enlighten me, please.
I put new gear oil in before starting. I checked my oil after the engine cooled down and it was milkey.
Okay, I?m confused. You put new oil in the drive and after the engine cooled down the oil was milky...which oil, drive or engine?
My problem is in my old pumphousing, I guess???
Ya? got another one right!!!! We?re still guessing here!
NOW....some experimenting.
Follow the water supply hose from the aft side of the water-cooled voltage regulator to the inlet nipple on the inboard side of the transom (dead center of the transom, above the drain plug, under the steering mechanism and coupler....kinda hard to reach/see) Replace this hose with nylon reinforced CLEAR tubing. Run the Maru on muffs not to exceed 1K r.p.m.s and check for full flow of inlet cooling water. Monitor the flow of cooling water and observe for bubbles. Also, keep a close eye on the temperature gauge. Allow the engine to warm and then feel the aft underside of the heat exchanger...it should be warm but not hot. If hot, insufficient cooling water is reaching the exchanger. Likewise, feel of the exhaust water from the prop/relief ports. This should also be warm but not hot and of full flow at least equal to an open garden hose.
Two weeks ago my M/C 470 heated up while out fishing. Here is what I found and steps taken to cure the problem:
