470 water pump/impeller question

[bently]

I have been fighting an overheating issue on my (1977) 3.7. I have the 4" heat exchanger and have now replaced the water pump impeller twice with no signs of damage or wear. The lower housing has been replaced and all water passages have been checked and no blockage. I reassembled the lower housing as it came off, but is it possible to assemble the plates and flat gaskets in a way to restrict the water flow of the impeller? I would really appreciate some photo or pdf that shows in well enough detail the order the lower housing should be assembled. This will help me cross off the impeller water flow from my list of possible issues.

Thanks

 

[Bt Doctur]

 

[Bt Doctur]

...

 

[mr 88]

Have you replaced the thermostat ?

 

[bently]

After I verify my water pump assembly is correct that is the next thing I plan on doing. I have also read about temp gauges reading hotter than the engine actually is and I have a lazer heat gun and it has shown me lower temps than what the gauge had displayed. I am going to get a low pressure gauge and start testing parts of the cooling system also but it does get frustrating when things check out but problem/issue still exist.

 

[bently]

I have a new question.

When I was running my boat on the muffs last night I noticed water running out of the gimble/bellows area. The water was cold and not from the spray out of the muffs. The watter comming out of the prop was definetly warm and my clear tube that supplys lake water to the heat exchanger was flowing. A while back when I removed my outdrive to check alignment there was an "O" ring the created a seal for the lake water pump, if this were to fall out of place could that be where the cooler water is coming from, or is there more that one possibility for the source of the water. If I correct this water leak that is between the water pump and heat exchanger my cooling issue should be solved as I feel this amout of additional water passing through my heat exchanger is what I am lacking.

Thanks

 

[Bondo]

I have a new question.

When I was running my boat on the muffs last night I noticed water running out of the gimble/bellows area. The water was cold and not from the spray out of the muffs. The watter comming out of the prop was definetly warm and my clear tube that supplys lake water to the heat exchanger was flowing. A while back when I removed my outdrive to check alignment there was an "O" ring the created a seal for the lake water pump, if this were to fall out of place could that be where the cooler water is coming from, or is there more that one possibility for the source of the water. If I correct this water leak that is between the water pump and heat exchanger my cooling issue should be solved as I feel this amout of additional water passing through my heat exchanger is what I am lacking.

Thanks

Ayuh,.... If the o-ring is missin', or outa place, Ya, that's a Problem,.....

There's also the Hose that carries the water from the gimbel housin', into the transom plate,....
It's up-in-over the exhaust bellows, sorta port-side,....

 

[Eric 3.7LX Alpha 1]

Time to pull the drive and have a look....

 

[bently]

I remove the outdrive and the tube that transfers the water from the lower unit to the gimble brackey was brittle and had a couple of holes in it which robbed the cooling system of water and water pressure to cool the antifreeze in the heat exchanger. It was not fun to replace but I got it done and you could noticably see the difference while on the muffs. While running it would warm up to right around 175-180 and sit there (guage could be off a little), when I add throttle she would drop down closer to 160. I believe I have exercised the demons out of my cooling system finally. It is like they say "Its always the last place you look/check".......

Thanks

 

[bfjou812]

You might want to remove the endcaps from the heat exchanger to make sure there is not any blockage. I fried an impeller once and didn't do this and the overheat didn't go away ,so I did the impeller again even though it was fine and finally checked the heat exchanger and found all kinds of garbage in it. Cleaned it out and now the boat won't get over 160 which is fine by me.

 

[stonyloam]

+1 bf, especially under the don't cap on the starboard side which is the inlet set of tubes where most of the larger stuff wil be trapped.