Mercruiser 170hp 470 3.7 impeller issue

[southwest395]

I have a 1986 mercruiser 170hp 470 3.7 4 cylinder. I installed a brand new impeller and housing this year. at idle speed no raw water. But if i put it in gear or rev the motor up threw the choke but I get raw water. Now i checked the raw water tubes inside no kinks. Raw water hose was replaced outside to and here a pick of it.

 

[86 century]

Re: Mercruiser 170hp 470 3.7 impeller issue

How about the little plastic tube that guides the water pipe in the upper to the pump body.

Had this get me one time

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

How about the little plastic tube that guides the water pipe in the upper to the pump body.

Had this get me one time

The plastic tube and housing all new. unless from the heat exchanger when it was leaking got back into the housing and did something

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

now when i take the front cap of the heat exchanger. i smell exhaust and get some pressure. Is this normal

 

[stonyloam]

Re: Mercruiser 170hp 470 3.7 impeller issue

that is just exhaust blowing back down the tube from the exhaust elbow. I guess you would say it is normal. But you have a serious problem between the pump and the exchanger. Either the new impeller has failed, the key that locks the impeller to the shaft is missing, the tube from the pump is not connected, the passage is blocked, or the hose is kinked. Going to have to drop the gearhousing again and try putting a hose in the tube to see if it is free of blockage, if it is not blocked you will have to take the pump apart again to see what is going on. BTW do not run it very long without cooling water flowing into the exhaust or you will cook your rubber parts, including the shutters.

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

OK question for you guys? What would cause the impeller rubber to burn into the housing and melt the plastic tube. Would this be caused if the previous heat exchanger was leaking coolant into the out drive and was over heating? At that point and time it was a new impeller and the heat exchanger was repaired twice and failed both times ? But at that time in was leaking coolant into the rear the second time. The first time was rear and front.

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

Here are some pics. Please tell me this was all caused by a bad heat exchanger and nothing else major.

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

Please any 470 members that may know or have gone threw this. Please let me know your thoughts thanks for the help.

 

[Don S]

Re: Mercruiser 170hp 470 3.7 impeller issue

That is caused by lack of water getting to the pump. Impossible to say why, could be defective pump housing, or leaking gasket or who knows. Replace the complete pump, lower base and all.

PS: Check the water pocket cover for damage as well.

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

What do you mean by lower base and what is the water pocket ?

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

I hope this is just a simple new impeller and gasket and housing and some gear oil for outdrive and then she ready.

 

[stonyloam]

Re: Mercruiser 170hp 470 3.7 impeller issue

Here: http://www.mercruiserparts.com/Show...&bnbr=110&bdesc=GEAR+HOUSING(DRIVESHAFT)+-+MR You ned everything from 24 (lower base) on up, pump housing and impeller. The water pocket cover is here: http://www.mercruiserparts.com/Show...br=80&bdesc=DRIVESHAFT+HOUSING+AND+DRIVESHAFT Take a look to see if it is badly burned, melted or warped. Take a close look at the rubber parts of the exhaust behind the engine to see if they ar damaged. Your shutters are likely shot, but you can check that later. Yeah those parts should do it.

 

[Bt Doctur]

Re: Mercruiser 170hp 470 3.7 impeller issue

You do have enough water going thru the hose to the muffs?

 

[southwest395]

Re: Mercruiser 170hp 470 3.7 impeller issue

You do have enough water going thru the hose to the muffs?

Yes i do. ive tried it in the lake and on muffs. But the previous heat exchanger was leaking into the out drive. So i dont know if the hot coolant would melt it or not.

 

[stonyloam]

Re: Mercruiser 170hp 470 3.7 impeller issue

Yes i do. ive tried it in the lake and on muffs. But the previous heat exchanger was leaking into the out drive. So i dont know if the hot coolant would melt it or not.

It would not. The hot uncooled (by exiting raw water) exhaust is what did the damage.

 

[ktbarrentine]

Re: Mercruiser 170hp 470 3.7 impeller issue

Have you found the missing impeller pieces? they will clog passages if not recovered.

 

[stonyloam]

Re: Mercruiser 170hp 470 3.7 impeller issue

Have you found the missing impeller pieces? they will clog passages if not recovered.

They should be under the front cap of the exchanger.