circulation pump question...

[benlh77]

'84 Mercruiser 5.7 898...<br />How can I check to see if the circulation pump is working correctly? Is it possible to pull it, change the impeller and it work if seal isn't broken? I have had a temp problem for the past few days that I can't resolve. The pump in the stern keeps melting, too. I didnt tighten it down too much or install it incorrectly either. I get good flow to the engine for a while until the exhaust gases burn the stern pump up. Only takes a few minutes at idle. I have good risers and exhaust manifolds (inspected them for crud and stuff). They get good flow, no clogging. I just think it might be the circulation pump. I checked all hoses inside and out, too.

 

[Bt Doctur]

Re: circulation pump question...

as lomg as the muffs are on correctly and have a good supply of water, the impeller should not be damaged.the circ pump would at most cause a slow rise in temp even though the flow out the exaust is good.

 

[benlh77]

Re: circulation pump question...

There isn't a good flow out of the exhaust. I see the exhaust gas but not much water. After the pump dies it stops spitting it out. I have the outdrive submerged past the intake holes in the bottom of a 50 gal drum with water flolwing in it at all times. Think that might have something to do with it?

 

[hullofalottatrouble]

Re: circulation pump question...

are you saying the impeller is melting? sounds like the water isnt getting from the drum to the impeller.. it shouldnt melt if its got good flow.. are the inlets clogged?

 

[benlh77]

Re: circulation pump question...

No, they are fine. I just tried using both(drum and flusher). I got good flow to the engine but there was a good bit of smoke coming out the exhaust and the temp rose (in about 4 mins) to 190. Would the circulation pump cause this?

 

[benlh77]

Re: circulation pump question...

The impeller isn't melting, it's the upper housing that does.

 

[hullofalottatrouble]

Re: circulation pump question...

did you change the impeller and then this started? <br /><br />did you noticed the overheat then open up the lower unit and notice the housing was melted?<br /><br />if you have a melted housing are you replacing it? are there any pieces that may have broken off that could be clogging the water hoses?

 

[Bt Doctur]

Re: circulation pump question...

"good flow to the engine" explain.<br />correct gaskets used, impeller keyway missing,copper connecting tube not in place correctly, completely clogged therm . housing.<br />regardless of the engine, water must flow from the pump, thru the therm housing , and bypass to the exaust system to cool the rubber components.

 

[Don S]

Re: circulation pump question...

If you have good flow of water to the engine, then either the thermostat is stuck shut, or the exhaust manifold and/or riser are plugged up. IF they are plugged up, then there is no water circulation at all, then you have an overheat.

 

[benlh77]

Re: circulation pump question...

correct gaskets, impeller keyway not missing, connecting tube in place, therm. housing not clogged. new thermostat (bought today) and manifold and risers free of obstruction. now, could it possibly be the circulation pump? I think thats the only thing left. I am out of ideas.

 

[benlh77]

Re: circulation pump question...

i changed the complete water pump set up each time it happened. i shut the engine down when it got to 190 and dropped the foot to find the melted impeller housing. as far as "good circulation", I pulled off the hose coming from the outdrive and there was a steady floe of water.

 

[Bt Doctur]

Re: circulation pump question...

sounds like enough water trying to get in, but no water coming out the manifold/riser.outside chance the wrong riser gasket was used sealing off or restricting the passages.<br />pull the drive, insert a hose from a washing machine cut in half into the water inlet of the gimbal housing.if this works, trouble is in the drive, if it dosent trouble is in the engine side.

 

[benlh77]

Re: circulation pump question...

no, I just bought new gaskets today and made sure they were correct. the old gaskets only had 2 sides with openings, it is supposed to have 4. I tried the hose in the water inlet yesterday and it ran through fine. I have spent several hours inspecting hoses, risers, exhausts and everything except for the circ. pump. I did unscrew a plug that was in the circ. pump to see if water shot out while engine was running and none did. Is it supposed to?

 

[benlh77]

Re: circulation pump question...

Is it ok to use an automotive water pump for marine use?

 

[Bt Doctur]

Re: circulation pump question...

"I tried the hose in the water inlet yesterday and it ran through fine."If this means that there was a good flow out the exaust(engine off) and the engine temp was elevated(when running)Id be suspect of the circ pump.if not this would prove your trouble to be in the drive section.You claim to have removed the hose going to the therm. housing and had good flow. I dont see how. even with the impeller removed you would still have enough flow from the hose pressure to cool the engine somewhat and flow out the exaust

 

[benlh77]

Re: circulation pump question...

I removed the hose coming from the outdrive while engine was running (just for a few secs to see if there was flow) and there was. I even have the outdrive in a half cut 50 gal drum with engine running and I had pressure. Good flow out of exhaust and engine temp. slowly elevating, like you said, I should be worried about the circ pump. I will change it out tomorrow and hopefully get good results. I appreciate your help.

 

[crawdadric]

Re: circulation pump question...

benlh77,<br />Mercstuff.com sells a cooling tool to help you isolate the problem. You take the drive off and attach the cooling tool to the drive, attach your garden hose to the fitting, run the water and start the engine.<br /><br />Tool can be found at mercstuff.com web page, click on tools and parts then click on number two water pumps, outdrive locks and cooling tools.