95 4.3lx alpha one mercruiser cooling system question

[nola mike]

OK, so I finally got a chance to get I to troubleshooting the issue. The impeller seemed to be drawing the water just fine, at idle I drained a 5gal bucket in about 2-3 min.

That's not nearly enough

 

[Jgcrock99]

That's not nearly enough

What should it be like.

 

[nola mike]

What should it be like.

Can't find the specs ATM, it's in a manual somewhere, but it's around 15 gpm. But I misread your post; drawing it from a bucket isn't a valid way to test it

 

[Jgcrock99]

In a vehicle, many times if the circulating pump fails there is a weep hole that helps identify the failure. Does this feature exist in marine applications? The 4.3 is just a truck motor so does this feature potentially exist for a marine application? Is there a way to identify of the circulation pump is working?

 

[dubs283]

if the circulating pump fails there is a weep hole that helps identify the failure. Does this feature exist in marine applications?.......... Is there a way to identify of the circulation pump is working?

Yes, there is a weep hole in the circ pump housing. Yes it will leak water if the shaft seal is failing.

Rarely does a freshwater run raw water cooled circ pump fail. If yours isnt leaking out the weep hole odds are against it having failed.

Your issue is too little raw water supply from the sea water pump. Either the impeller/pump housing has failed or there is a blockage/leak between the pump and t stat housing

 

[Jgcrock99]

Yes, there is a weep hole in the circ pump housing. Yes it will leak water if the shaft seal is failing.

Rarely does a freshwater run raw water cooled circ pump fail. If yours isnt leaking out the weep hole odds are against it having failed.

Your issue is too little raw water supply from the sea water pump. Either the impeller/pump housing has failed or there is a blockage/leak between the pump and t stat housing

Thank you. No leaking from the pump which is why I mentioned it, just trying to identify the problem. I'm new to working on marine applications myself so trying to learn. Impeller seemed to work when tested but may just not be delivering enough water, not sure what the flow rate should be. Water was pulling from the muffs and coming out the transom as it should but still began to overheat. I'm at year 3 on my impeller so going to replace and recheck everything. Tstat is easy to access so going to remove if present and retest there as well. Thank you.

 

[Bondo]

Thank you. No leaking from the pump which is why I mentioned it, just trying to identify the problem. I'm new to working on marine applications myself so trying to learn. Impeller seemed to work when tested but may just not be delivering enough water, not sure what the flow rate should be. Water was pulling from the muffs and coming out the transom as it should but still began to overheat. I'm at year 3 on my impeller so going to replace and recheck everything. Tstat is easy to access so going to remove if present and retest there as well. Thank you.

Ayuh,.... The simplest test is to pull the in-coming hose off the t-stat housing, 'n hold it pointed straight up,.....
At idle, the water stream should go up 5 / 6", before it falls over on itself,....

 

[Scott06]

Per the merc manual the pump should output at the hose 3-4 qts in 15 seconds (lower flow at higher gear reduction drives)

 

[nola mike]

Per the merc manual the pump should output at the hose 3-4 qts in 15 seconds (lower flow at higher gear reduction drives)

Hmm, I thought it was gallons. I couldn't find which manual it was in, though I remember it being somewhere. Where is it?

 

[Scott06]

Hmm, I thought it was gallons. I couldn't find which manual it was in, though I remember it being somewhere. Where is it?

I believe Its in the outdrive manuals but would have to check to be sure which manual. I have a screen shot on my phone from last time this came up

For sure it is quarts per 15 seconds so basically 3-4 gallons per minute

Edit- I was wrong I got that screen shot from manual 24 which is the 5.0 and 5.7 GM V8 engine manual pg 732 of the pdf (6A-11 in the manual) ...

 

[Jgcrock99]

Yes, there is a weep hole in the circ pump housing. Yes it will leak water if the shaft seal is failing.

Rarely does a freshwater run raw water cooled circ pump fail. If yours isnt leaking out the weep hole odds are against it having failed.

Your issue is too little raw water supply from the sea water pump. Either the impeller/pump housing has failed or there is a blockage/leak between the pump and t stat housing

OK so, new impeller and is functioning fine. I actually removed my thermostat to eliminate it as an issue, waiting for the new one to come in but wanted to test. Boat ran cool for about 10 min on the muffs then it started heatind up again. There are square head plugs in my circulation pump, can I remove these to inspect the pump before removal? Where would a blockage be? Water is coming out the ports in the transom, does water not have to go through the circulation pump before exiting here?

 

[Jgcrock99]

Ayuh,.... The simplest test is to pull the in-coming hose off the t-stat housing, 'n hold it pointed straight up,.....
At idle, the water stream should go up 5 / 6", before it falls over on itself,....

Missed this message, thank you, I'll try that

 

[stresspoint]

sounds as if you may have a leaking O ring where the drive meets the upper housing , if you are sucking air there it will not get enough water to the motor.
a new one comes with the gasket set and it needs to be glued in place before fitting the out drive.
corrosion is common there , but you are fresh water so guessing its the O just failed from age.

 

[dubs283]

sounds as if you may have a leaking O ring where the drive meets the upper housing , if you are sucking air there it will not get enough water to the motor.

The mating surface/oring you're referring to is on the pressure/output side of the pump. It would be leaking water if it's failed not drawing air in

Would be obvious on muffs with a sound sea water pump

 

[Jgcrock99]

Finally figured it out. Water line had pulled off the out drive so nothing was getting to the motor. Due to the way the water was pouring during muff testing it looked like it was coming from the right spots. Should there be a hose clamp on the drive side of that heater hose? I ask because mine apparently had a zip tie from the last person that took out my motor last year because this is my first time fooling with it. I was able to get the hose back on but I'm not able to get anything to hold it on without pulling off the drive I'm assuming. I attempted to put a hose clamp on but no good way to get to it. Ran it as is and everything works so if I get this situated it's good to go.

 

[Scott06]

Finally figured it out. Water line had pulled off the out drive so nothing was getting to the motor. Due to the way the water was pouring during muff testing it looked like it was coming from the right spots. Should there be a hose clamp on the drive side of that heater hose? I ask because mine apparently had a zip tie from the last person that took out my motor last year because this is my first time fooling with it. I was able to get the hose back on but I'm not able to get anything to hold it on without pulling off the drive I'm assuming. I attempted to put a hose clamp on but no good way to get to it. Ran it as is and everything works so if I get this situated it's good to go.

yes hose clamp on both sides. Only thing that uses zip ties are the gear lube line on gen 2s and folks use them on the shift bellows to shift cable connection.

I think if you take your hinge pins off you should be able to pull the bellhousing back with out disconnecting the bellows. might provide some more room.

Best bet is to get your hands on a factory manual for the outdrive they have good step by step instructions for how to reseal the transom assy.

 

[Jgcrock99]

yes hose clamp on both sides. Only thing that uses zip ties are the gear lube line on gen 2s and folks use them on the shift bellows to shift cable connection.

I think if you take your hinge pins off you should be able to pull the bellhousing back with out disconnecting the bellows. might provide some more room.

Best bet is to get your hands on a factory manual for the outdrive they have good step by step instructions for how to reseal the transom assy.

Thank you! So the drive side outlet is a barbed connection, does this connection need bellow adhesive and a hose clamp or should this be a clamp only. I'm going to tackle it over the next couple of days so I want to make sure. I bought the adhesive but don't want to screw anything up. If it's barbed I know the adhesive probably won't be very beneficial but could be wrong.

 

[dubs283]

No need for adhesive, it's not required

The worm gear portion of the clamp must be oriented parallel to the outer edge of the bell housing, it's the only way you'll be able to access it for tightening

 

[Jgcrock99]

No need for adhesive, it's not required

The worm gear portion of the clamp must be oriented parallel to the outer edge of the bell housing, it's the only way you'll be able to access it for tightening

I think I'm all good. Replaced thermostat and all gaskets, I was able to get the hose back in place without removing any of the bellows or other items. It was difficult for sure but I believe everything is good to go. Muff test was successful, boat achieved operating temperature and sustained it without issue. I did notice that the water coming out of the transom was much warmer on one side than the other, specifically starboard was warm and port was cool, is this normal/ok? Thank you everyone that chimed in. I'm pretty good overall at working on things but this marine stuff is all new to me, this forum has been huge and very helpful each time I've used it.