454 overheating

Hey Wes? This Stu guy just showed up and is trying to hijack this thread. Can you chastise him?
 
I got to say this is the funniest thread I have ever posted, you guys are killing me
 
Yes, the Alpha 1 has the impeller in the outdrive. You need to split the upper and lower to replace it. Not a hard job if you have some mechanical ability.

If it seems to overheat at idle or slightly above, it would appear that the impeller is not moving enough water. Have you grounded the boat lately and possibly sucked up some sand? Sand and debris tend to ruin impellers rather quickly. You may start with the impeller and thermostat and then see if the problem still exists. If so, I would check the power steering cooler and then I'd pull the manifolds and risers to inspect.

Doug
 
go with the t/stat like you first mentioned and let us know how you make out. after that you will still have to look at the impeller as it only takes one time of sucking up dirt/mud/sand or some other crap to trash an impeller...good luck
 
Just when you thought that the ball thing was over.......

I'm not sure about your era 454, but my 1983 5.7 with alpha I OD was raw water cooled and had two plastic balls on a spring inside the goose neck where the thermostat is housed. (I'm sure I just opened a door) Sometimes debris like grass will hang on those balls and keep them open/closed. Those white plastic balls are a bypass for low speed cooling. Your springs or balls may be out of whack....

....Ok, have at it...
 
osd9, I will take a look but I don't see anything like that in the Service manual, thanks
 
Does you t-stat housing look like this?

tstat12.jpg
 
There they are......That's those little white balls.....and I'll bet you thought I was making that up....
 
This sure sounds like an impeller problem to me. Easy to go after if the boat is on a trailer. Thermostat would be a less likely choice. BTW: Although rated to last longer, my mechanic recommends replacing impellers (need it or not) every two seasons.

I hear the point about the risers and manifolds getting hot after slowing down. Could even be true, but that is not where the temperature sensors are located on my 5.7 engine: They are right at the thermostat housing. That cools really, really quick.

As for the I/O drives: The Alpha 1 drives pick up water through the I/O unit. The bravo's use a through hull. The Alpha 1 does not have a forward facing scoop by any stretch of the imagination. There are slots on the sides that allow water to flow into the unit.
 
comsnark said:
This sure sounds like an impeller problem to me. Easy to go after if the boat is on a trailer. Thermostat would be a less likely choice. BTW: Although rated to last longer, my mechanic recommends replacing impellers (need it or not) every two seasons.

I hear the point about the risers and manifolds getting hot after slowing down. Could even be true, but that is not where the temperature sensors are located on my 5.7 engine: They are right at the thermostat housing. That cools really, really quick.

As for the I/O drives: The Alpha 1 drives pick up water through the I/O unit. The bravo's use a through hull. The Alpha 1 does not have a forward facing scoop by any stretch of the imagination. There are slots on the sides that allow water to flow into the unit.
Click to expand...
Your bravo comment is not correct.
 
Really? Crap. That is what I was told in the past.

Red ball for me.

Edit: I see my confusion. The pump is on the motor, but the pickup is still in the drive. :smt021 My bad.
 
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comsnark said:
.....I hear the point about the risers and manifolds getting hot after slowing down. Could even be true, but that is not where the temperature sensors are located on my 5.7 engine: They are right at the thermostat housing. That cools really, really quick....
Click to expand...

That's because it is in the begining of the raw water circuit...before the manifolds....the 'exhaust' manifolds are attached to the biggest heat manufacturing center of the power plant....it's the radiator so to speak...keeps heating, and heating and heating.....
 
agreed. . . .and honestly the only time I check the temp on those is if I suspect there is a problem. (requires the hatch to be up, which raises the entire rear seating area and basically looks like a drag brake when raised -> I won't open it casually when running)
 
Woody said:
Your bravo comment is not correct.
Click to expand...

Some.
My Bravo III has a separate Pulley driven RawWater pump mounted on a bracket attached to the engine but pulls through the leg.

Some Bravo II's have a through hull seacock that pick up and to that same pump.
 
comsnark said:
I am not quite sure this explanation is on target.

First, what engine do you have? Most mercruiser's have TWO temperature sensors, one wired to the temperature gauge and the other wired to the engine temperature alarm. If you peg the gauge, but the alarm doesn't go off. . .then there is a good chance it is a sensor.

But I would not rule out a bad sensor AND an overheat problem.

I would think the first things to check are the sensors and thermostat -> just because they are easy. Impellers would be the next thing to check. I forget where the BIII impellers are located. They can be replaced with the boat in the water right? Only the Alpha drives have the impellers in the "drive" and require the boat out of the water.

On my boat, once the engines warm up I NEVER see the temperature gauges move. The thermostats control the engine temperatures throught out the operating range, and control them well.

If you are seeing the gauges move during some part of the operation of the boat, then I would suggest that either the thermostats are being slow to respond OR the cooling system is not adequate in some way. Regardless. . .if the temps stay under 180-190F, I would not loose sleep over it.
Click to expand...
Useing this thread as an example.....The OP states his engine "usually runs around 145 degrees" and your response is "if the temps stay under 180-190F, I wouldn't loose sleep over it". Why shouldn't a 30% increase over normal gauge readings(pick any guage) be reason for concern? What would be the point in having gauges or even ever looking at them? Not throwing red at you, just sitting here thinking.
 
Yeah. . .no sweat. I take no offense at being corrected for a clear technical error.

- - - - - -

What I meant here was if the temperature climbs to 180-190F, and then comes down immediately I would not loose sleep over it. RonDDS and Dom both say this is normal (I think they are refering specifically to exhaust components). If the temperature goes up and stays up. .. I wouldn't lose sleep over it, but something needs to be fixed and soon.

The real issue is if any part of the cooling system is getting over 210** or so. If that is the case, then you are going to have some boiling water. .. boiling water is very bad in that you now have to deal with STEAM in the cooling system. . and the system is not designed to get rid of that. The steam will choke the system, and actually impede the flow of liquid water through the system. . .so the problem escalates quickly. That would be very bad.

- - - - - - -

My view is that you CAN run at 190F for a while with no real issue. . .the problem is STAYING at that temeperature. Being above your normal operating temperature means that you are now cooling system limited. I don't think boats are designed to be cooling limited. If you run like this and something degrades further. . .you are AT overheat city.

If my gauges come up and stay up. . I will be watching them like a hawk watching a limping mouse.

- - - - - - -

I was going to quibble regarding the 30% statement, but running some numbers quickly. . . going from 145F to 190F is alot more serious than I first thought. Heat removal is a function of water flow and temperature rise. Assuming a 80F supply. . .going from 145F water at the thermostat to 190F water implies a 70% difference in water flow relative to what you should have as a minimum. Probably not as bad as that. . .as the coolers get notably less efficient as water temps rise. But still. . .that ain't good.

Ok. . thinking harder about my experiences, my engines normally run 170F. . . if the gauge climbs to 190F. .. that implies a 22% change relative to what I should have as a minimum. I have run in that condition with no adverse affects. . but not for long. When it happened, either the temperatures came down to normal. . .. or moved to the "pegged" side of the gauge.



**distilled water boils at 212F at sea level. In an engine, the water is slightly pressurized, so the boiling point will go up a few degrees. Further, if you are dealing with salt water, the boiling point will go up another few degrees. But how accurate are your temperature sensors?
 
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