Another 3.7 470 question

[hadaveha]

Im getting ready to order my impeller kit for the outdrive, being that these engines are so heat stressed, is there a better impeller kit or aftermarket impeller that pushes more raw water through the system than others.

 

[Bondo]

Re: Another 3.7 470 question

Im getting ready to order my impeller kit for the outdrive, being that these engines are so heat stressed, is there a better impeller kit or aftermarket impeller that pushes more raw water through the system than others.

Nope,... Not really,.... Globe makes a "Run dry" impeller, but it don't move more water,....
The displacement of the pump can't get any bigger,...

 

[hadaveha]

Re: Another 3.7 470 question

thank you bondo I didnt think so, just grabbing at straws hoping someone had better luck with one over the other

 

[Maclin]

Re: Another 3.7 470 question

Hadaveha, does yours have the 4" heat exchanger? If your is the 3" then going to the 4" has to help some I would think.

 

[hadaveha]

Re: Another 3.7 470 question

ya Maclin it does have the 4inch I was just changing the impeller anyways so I thought I would ask if anyone had any really good luck out of 1 impeller vs another

 

[stonyloam]

Re: Another 3.7 470 question

If this is a new to you engine, change the whole thing, pump housing along with the impeller. Then a new impeller every other year and as long as you don't run it dry you should not have to worry about the impeller. Use OEM parts this time. Aftermarket impellers are OK if you are changing every second year.

 

[hadaveha]

Re: Another 3.7 470 question

OEM kit on the way Ill be watching the youtube vids tonight I know there is a cpl vids on there about chanking the impeller on a alpha 1

 

[hadaveha]

Re: Another 3.7 470 question

I have a 1984 470 thats in the boat Im working on, and rotten donar boat with a 1988 470, the donar has aluminum exhaust, should I change over to the aluminum even if I find no problems with cast iron thats on the boat now.

 

[stonyloam]

Re: Another 3.7 470 question

If the Al one is in good shape, IMHO, go with that one. You need to change the reservoir along with the manifold. Note the gasket and reservoir part numbers here: https://www.mercruiserparts.com/selectDocs.asp?doc_nbr=12488

 

[tazrig]

Re: Another 3.7 470 question

I had a pair of those 470's once. Constant overheating. All you can really do is switch to the 4 inch heat exchanger and try to keep all passages as free as possible.

 

[stonyloam]

Re: Another 3.7 470 question

I had a pair of those 470's once. Constant overheating. All you can really do is switch to the 4 inch heat exchanger and try to keep all passages as free as possible.

If you are overheating ( with new impellers) check to see if you have a restriction in the exhaust elbow that is cutting down the water flow through the exchanger. There should be little back pressure if you put a garden hose in the aft hose on the exchanger that goes up to the elbow.