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Discussion Starter · #1 ·
Hi
I could use some advice on this.

I have a 1989 regal with a 454 mercruiser bravo one outdrive. I fired it up this year and noticed after a few minutes my temp gauge gets up to temp then slowly starts running hot.

I removed the impeller pump and checked the impeller ,looks fine (it was replaced 2 years ago). I also replaced the thermostat, didnt make a difference. Also removed the hoses to look for blockage and they seem fine.

what would be the next step,replacing the circulating water pump?

Any thoughts are appreciated.

thanks
bill
 

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Is the circulating pump leaking when the motor is running? That's a usual failure mode.

Is the power steering cooler or the oil cooler blocked by debris? Are the manifolds blocked up? Do the manifolds get hot to the touch? (they should get good and warm, but not hot enough to burn you).

How high does the temp gauge get?
 

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Sorry, I can't offer expert advice, but FWIW, what comes to mind...

I know I'd certainly be thinking circulating water pump at this point too. But, kind of seems like a long shot though.

What about replacing the temp sender. Perhaps it is reading high???

What about sediment/rust in the cooling passages? Does it seem especially dirty if you pull a drain plug?

Any sign of rust on the exhaust manifolds where the risers bolt on? Perhaps it's time for new manifolds???

Hopefully others can offer better suggestions.

Good luck!!
 

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Discussion Starter · #4 ·
manifolds get warm thats about it.engine appears to be running normal and is cycling water,I dont see any leaks around the circulating pump but I will check again.

The longer I let the motor run the higher my temp gauge climbs. I dunno, I am thinkin either circulating pump or gauge is bad.
 

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if you rev it, does the temp rise or fall?

It could be the circulating pump. But I know some high performance boats eliminate the circulating pump completely and replace it with a bypass, so I'm thinking it's not all that critical. Could also be the impeller. Not sure if "looks fine" is a good enough indicator of "is fine", all I know is that if i'm bothering to take it out i'm putting a new one back in.
 

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QUOTE(sleeper @ Jun 18 2009, 10:41 AM) <{POST_SNAPBACK}>if you rev it, does the temp rise or fall?

It could be the circulating pump. But I know some high performance boats eliminate the circulating pump completely and replace it with a bypass, so I'm thinking it's not all that critical. Could also be the impeller. Not sure if "looks fine" is a good enough indicator of "is fine", all I know is that if i'm bothering to take it out i'm putting a new one back in.
i agree, especially if you had it out, i would have just replaced it.
i have had ones that looked ok, but changing them made a huge difference.
impellers dont need to be broken or brittle to fail, then get a "seat", or a shape rather, to them sometimes and that can slow the progress.
change that, if you still have the problem i would guess gauge may have bad ground or connection, check that and clean, then possibly the sender could be bad.
if the mannies are not getting super hot it doesnt sound like its NOT getting water, or even restrictive flow.
how does the water flow compare to normal out the exhaust?
 

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Discussion Starter · #7 ·
Well I replaced the Temp Sender and thats not it. I rev the engine and it seems to hold at that temp and not climb,until I let off and back to idle then the temp starts to climb.

Any ideas ?

I am still going to check for a blockage somewhere. The impeller looks to be in good shape (no broken fins) although when I removed it, it has taken the curved shape of the housing.

Could this be causing my problem?
 

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If the impeller has hardened at all and has that permanently "curled over" look, it's time to replace. It will not move as much water when the blades don't flex properly. Most manufacturers reccommend impeller replacement every year... I gotten as many as 4 years, but that's really pushing it and asking for problems.
 

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Well, if nothing else, changing the impeller is an inexpensive next step, so it's worth a try.

Good luck!
 

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QUOTE(Capn Ken @ Jun 19 2009, 12:41 PM) <{POST_SNAPBACK}>If the impeller has hardened at all and has that permanently "curled over" look, it's time to replace. It will not move as much water when the blades don't flex properly. Most manufacturers reccommend impeller replacement every year... I gotten as many as 4 years, but that's really pushing it and asking for problems.
yep, swap it out, its time.
you'll notice a difference
 

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Discussion Starter · #11 ·
Just replaced the impeller and guess what? Thats not it.


Looks like water circulation pump next. Damn!

I"ll update as soon as i can.
 

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Sorry I don't have any info for you or hints. But Im having the same problem myself, the impeller was replaced last season an then 2 seasons before. Today the boat started heating up.
Boat heats up at idle, an cools at 2000+ rpm. So I put the motor at 2000+ rpm an squeezed the hose that feeds the motor from the outdrive an it feels as if no pressure is their.
My question is is their something that can cause an impeller to go bad besides sand an ect that it sucks up? Like a shaft seal worn shaft or something???

I know that your suppose to replace them regularly but 3 impellers in 3 1/2 seasons??? I didn't even use the boat that much last year, less than 25 hrs an less than 10 hrs this year, that just ridiculous for it just being replaced. Any tips an info would be great also recommendations of were I can get the kit at a good price? Alpha One Gen 1 1989. Im not looking to order off the net either.

Didn't mean to hijack thread but i didn't see a reason to start another one.

Thanks much appreciated
 

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Impeller pump not assembled correctly.

Between the gaskets and metal plate there is something not aligned.

Reduced water flow can only be either the assembly or raw water screens/filter.

Something is not allowing the mass to flow into the circulating pump.
 

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QUOTE(Gutters @ Jun 19 2009, 08:49 PM) <{POST_SNAPBACK}>Alpha One Gen 1 1989.

Totally different than the reply I gave above (was for Bravo or inboard) since Alpha's use an impeller located in the outdrive, whereas Bravo's (and inboards) use an impeller attached to the motor with a raw water port in the hull and engine driven (off the motor with a belt and pulley) pump.

In an Alpha you need to reseal the drive; that means to remove the outdrive, break apart the lower from the upper, and check/replace the impeller housing. Most times these go bad because they are "plastic" or in someway not assembled correctly. Look at the pressure plate to uneven wear, scores or scoring in an uneven rotation, bent/broken or otherwise damaged veins, or other discrepancies.

To seal a lower in an outdrive I would suggest a certified Mercury Mechanic. There are procedures that need to be followed and a "shade tree" mechanic does not qualify.
 

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Discussion Starter · #16 ·
I pulled out the exhaust flappers and they were wasted. Could this be what has been causing my overheating problem?

I also removed the risers and checked down the Y pipe for any debris and all appears good.

Bill
 

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My overheating ruined my exhaust flappers, My over heating was caused by oil cooler for power steering being clogged with zebra muscles, tried everything you have talked about and it ended up being something that just needed to be rinsed out. Hope you fig it out .
 

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Discussion Starter · #19 ·
I checked the new thermostat today in a pot of water today,with a meat thermometer. Got water to temp to 160 and it never opened. Got another one installed it and seems to be working fine.

I think I got it figured out.
Lesson learned here, check your thermostat even if its new.
 
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