Cooling Issue- Advice Needed

S

seachunk2

Member
Joined
Apr 16, 2006
RO Number
20886
Messages
131
Hi All. I have a 1995 raw water cooled 4.3LX Mercruiser I/O with an Alpha 1 Gen II outdrive that I've owned since 1999. I trailer the boat and always fresh water flush the engine with a standard motor flusher. I've been too busy with work & haven't started the boat for about 2 months. Two weeks ago I started it up in the driveway and the engine over heated. Water wasn't flowing through the motor so nothing was coming out the outdrive exhaust holes. I've since replaced the impeller with OEM new including all gaskets and seals. Pump housing was fine- no grooves. Cleaned up like-new. I also suspected that the thermostat might be frozen so I just pulled it from the housing just to eliminate it as a culprit. I'll put a new on in the Spring. I also checked the circulation pump mounted on the front of the motor. The bearing spun smooth & freely with no play. The impeller inside appeared to be solidly connected. No leaking from the weep holes either. I cleaned out both engine block drains with a wire hanger and I get a steady stream flowing with the engine running.

When I restart the motor, water will come out the outdrive drain but seems to take even longer to do so than when I had the t-stat in place.

I disconnected the water supply hose that comes from the rear and connects to the T-stat housing. Water comes out in large gulps, not a steady stream. There isn't much pressure so the gulp's range is maybe an inch or two before it drops. That seem a bit weak.

Any thoughts as to whether this is normal? This is my first time inspecting the flow of water from the impeller as it flows out the hose at the housing end. Please keep in mine that I'm working off a garden hose fed motor flush.

Since I winterized the motor and had the boat wrappped today, this is just something I'll think about this winter as I await the return of Spring. In the spring I'll reinstall the T-stat and launch it to see how the the engine is cooled. I'm sure that the motor flush is not a good way to be troubleshooting this situation.

Nonetheless your comments will be appreciated.

Happy Veterans Day to all our vets!
 
As far as it taking a lot longer for the cooling water to come out the outdrive...I'm not a marine mechanic, but that sounds right to me.
Think about it, when the engine is cold, having a T-stat helps it warm up quickly, by diverting most of the cooling water away from the engine block, straight to the exhaust, a very short pathway. Without the T-stat, all that cooling water goes into the block which is a much longer pathway to the outdrive drain meaning it will take longer to get there.
I'm sure if I'm wrong on this, more qualified RO's will correct me.
 
Check the t-stat operation in a pot of warming water with a candy thermometer to show temp when it opens. Hang the t-stat so it's off the bottom.

If that engine employs (spring-loaded ball) RW bypass "poppet valves" on either side of the t-stat housing , you might check to see if they move freely and are intact.

If the hose muffs were in fact in correct position and tight and supplying maximum available water flow correctly , the "gulping" flow downstream might possibly indicate a suction air leak ...(or still just pushing out trapped air.) You kept RPM near idle , yes? House supply can't provide sufficient flow for elevated RPM .
 
Thanks for these replies. The engine no longer appears to be running hot. This motor does not have the poppet valves.

Was the improvement due to the removal of the T-Stat or installation of the new impeller? I don't know.

I suppose that had I of found a definite cause of the problem such as a stuck T-Stat or bad impeller I feel more confident. Since I have 18 years flushing this motor the exact same way for all these years I confident it wasn't that I did something wrong. I also can't find a fault in any of the components.

I won't know if there's still a problem until I re-install the T-stat in spring and run the boat while it's in the water rather than with the muffs. Hopefully it won't overheat. If it runs normal, I'll re-test the water hose coming out of the water supply hose located on the T-stat housing just to see what the water flow should be. I would expect that the flow will be with a larger volume and more steady as opposed to a gulping when it's running with off the garden hose setup.

Just another good reason why I can't wait for this winter to be over!

If the T-stat was the culprit because it wasn't opening when hot,I believe I would still get water coming out of the outdrive exhaust ports. I'm pretty sure I threw out the old T-stat so I can't test it. I already bought a brand new mercruiser T-stat, which I'll install in the spring.

Fortunately, aside from it taking at least 5 minutes of idling for water to eject out the outdrive ports, once the water started coming out and I switched to running pink AF to winterize the motor,things went OK.

What CWMS mentioned is making sense but no water was coming out of the outdrive when the old T-stat was in place or after I removed it a re-ran the motor.
 
I'd pen up a block drain to collect some of the antifreeze water mix to see if you got enough antifreeze in the block. Put it in the freezer to see if it freezes. This method of engine winterizing worries me because it's a crap shoot as to if the mix is good enough.
 
Just to make sure you're seeing it correctly, very little water comes out of the prop. Most comes out of the bottom ports on the outside transom assembly.

Now, one possible problem that can happen if running a while on the hose with little or no water coming out. Not enuff water(hot exhaust) can damage the rubber seal between the water pump and the upper. There is a metal tube with a plastic guide tube. It should fit into a rubber seal on the upper. You can seat the plastic tube in the seal of the upper and the metal tube is guided by the plastic tube.

I hope this is understandable...my mind wanders a bit lately. I hit 70 today.
 
quote:
Originally posted by jtybt15
I hit 70 today.
Click to expand...


HAPPY BIRTHDAY, FRIEND!!!

For the rest of you, Charlie's among the best of our good guys. And definitely our MerCruiser Guru.
First to reply to my first post here on BE, about a dozen years ago.

Again, Happy Birthday Charlie!
 
I guess I'll be catching up to you pretty soon.[:P]
 
Happy Birthday Charlie! Welcome to ~The Geezer Club [:-hspin] (It meets most every Fri. at Offshore Ale & Oyster). Only ~~40 more years to go before your expiration date , so make'em count! [:-thumbu]
 
Happy Bday Charlie! My daughter shares the day with you...it's her Bday as well although she's exactly half your age!

As far as the motor cooling issue goes, I had coolant coming out of the bottom ports on the outside transom assembly while flushing. I ran a total of 5 gallons through the system via the muffs. I know some doesn't make it in to the motor but enough did since what was coming out the ports was pink. It started turning pink by the #2 gallon & there were an additional 3 gallons that followed. Hopefully most of the residual water was flushed out by the antifreeze so the antifreeze remaining in the motor isn't too diluted. I also poured AF into the from the opening in the manifold where the t-Stat housing connects until it was filled. The boats winterized & covered and put away for the season.
 
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