Merc 470 water temp question

[bently]

I have an old 470 which I replaced the water pump and lower housing in early summer last year, I have also upgraded to a 4" heat exchanger. When I run the boat on muffs the water temp verys from 170 to 185, drops when throtle is increase but slowley climes when in just idle. Is this a thermostat issue or am I good to go and just watch the temp when running her?

Thanks

 

[Bt Doctur]

Re: Merc 470 water temp question

thinking the riser is getting slightly plugged up

 

[Eric 3.7LX Alpha 1]

Re: Merc 470 water temp question

My 3.7 with the 4" exchanger and a good impeller won't budge off 160? running it at idle or underway. The only time I've had temps that high was with a worn impeller.

Personally I would not feel comfortable with getting up to 185?.

 

[stonyloam]

Re: Merc 470 water temp question

Interesting, seems like if the exhaust elbow were plugging, it would be the other way around, with overheating at higher RPM. To check it out, remove the rear hose off the exchanger that goes up to the fitting on the elbow. Stick a garden hose in it and see if the water flows freely with little backpressure. Does not sound lika a thermostat. It sounds to me like you are just not pumping enough water through the exchanger at low RPM. If the elbow is clear, look at the impeller and housing again.

 

[bently]

Re: Merc 470 water temp question

I would hope it is not the impeller because it has maybe 3 to 4 hrs max of run time and it was never out of the water when ran. Is there a good diagram for the orientation of the plates that go in the water pump between the lower and upper housing? I will take a good look at my riser this weekend.

Thanks

 

[wrestling coach]

Re: Merc 470 water temp question

I have also upgraded to a 4" exchanger. Before it went on the engine it went to a radiator shop to be cleaned and pressure checked. I hope you did the same. Like Eric mine will not move off 160* under any running conditions since the upgrade.
Dennis

 

[dubs283]

Re: Merc 470 water temp question

I would hope it is not the impeller because it has maybe 3 to 4 hrs max of run time and it was never out of the water when ran.

was the impeller OEM??

was the whole water pump kit and base assy installed or just impeller??

 

[bently]

Re: Merc 470 water temp question

I replaced the impeller kit and lower housing at the same time. The upper housing did not show sines of being overheated and distorted. I do have some issues with the heat exchanger end cap gaskets, both ends there is a slow drip. I have tried to tighten them with a wrench and I back it off a little and the water does spray from pressure out of the end caps but I can not get them to be completely dry with no drips.

 

[bently]

Re: Merc 470 water temp question

I believe the water pump kit and housing part numbers were given to me when I asked the question on this site last year, so they should have been the correct ones. Everything seemed to fit fine.

 

[bently]

Re: Merc 470 water temp question

Here are some pictures of my riser and where I think exhaust flappers should be (missing) in the lower section that goes out the hub.



When I took the riser off I could feel water slaushing around in it and when I ran water through it with a garden hose it first was rusty and then cleared up but ran though pretty easy.

 

[stonyloam]

Re: Merc 470 water temp question

Yeah the shutter is gone. Since the elbow seems clear, chances are it is the impeller. Best bet might be to get an OEM impeller and pump housing. Pop the end caps off the exchanger and make sure all is clear there. New end cap gaskets might be in order.

 

[bently]

Re: Merc 470 water temp question

I have ordered:
exhaust shutters
exhaust bellows
Riser gasket
OEM impeller
heat exchanger end cap gaskets

What I would like is a good view of the impeller and the layers of plates for the reassembly of the water pump, incase I have one in the wrong place restricting the water flow.

Thanks

 

[Eric 3.7LX Alpha 1]

Re: Merc 470 water temp question

Pull the drive and run the engine off the hose.

Just take your garden hose and stick it in the water inlet of the bellhousing. Get it in there as far as you can and run it. (Where the O'ring is)

Fire it up and watch the temp. If it's the impeller causing the higher temps you will know it.

 

[JerryIrons]

Re: Merc 470 water temp question

You can also check that water hose that connects from the gimbal housing to the bell housing for a kink. And check to make sure that it's connected as well! I had one come loose once and partially separate for a while, but still sort of worked.

 

[bently]

The exhaust flappers were a pain in the a$$ to put in but they are there now. I put a clear hose from the incoming lake water fitting on the gimbal housing that goes to the heat exchanger. I now can see the flow of water to the exhanger, there was a splice where the voltage regulator was and with that gone, I beleave I get more water flow now. The temp guage on my boat doesn't show as hot as I was getting before. I am going to borrow a buddies lazer heat gun and see how hot the metal parts are actually getting and that will tell me if my guage is off and if my thermostat is openning when it should.