melted tube alpha one

coastalcruiser · Sep 12, 2007

Hi I have a 888 302 Fresh water cooled Mercruiser with a alpha one lower unit
the engine just had the head gaskets changed and de-carboned by me and is now looking and running great after cleaning everything, lots of tlc and painting all the parts
I have had the heat exchanger and the manifolds\risers cleaned out at the rad shop new thernostat and flushed out
It's overheating on a plane only so I took the lower unit off. melted tube and a soft gasket that is also looking real bad the pump cover is blistered badly
I'm happy because this means it will work again but for how long?
I did the pump last year
The outdrive has good clean oil, it was just serviced last year
So question is how did I get the meltdown? only thing I can think of is hot exhaust did that but what things do I need to do now that it's melting?
I'm taking a break but next I plan on testing the copper tube it feels loose with a garden hose to pressure test and back flush
btw I have a 4 cylinder transom(where the steering is and the leg attaches to) it's got a exhaust tube that looks different than the 8 cylinder one that a mechanic helped me replace I think it's causing too much heat
I'm almost there...it's been allot of work

coastalcruiser · Sep 12, 2007

Re: melted tube alpha one

there is a flapper stuck on the bottom of the lower unit

Haut Medoc · Sep 12, 2007

Re: melted tube alpha one

You replaced the y pipe with what?......

Your post does not make sense......
The exhaust shutter burned off from excessive heat.......
On a 888 system the only place for cooling water to exit is through the dumps on the risers......
My guess is that they are clogged with scale & need to be replaced even if you had them cleaned at a radiator shop......
You don't clean risers once they degrade, you replace them.......

coastalcruiser · Sep 12, 2007

Re: melted tube alpha one

sorry my post doesnt make sense
the rubber flapper must have worn out.
your right it must have been from a clogged riser.
I didnt know you need to replace risers.

thanks for your reply

Haut Medoc · Sep 12, 2007

Re: melted tube alpha one

coastalcruiser said:
sorry my post doesnt make sense
the rubber flapper must have worn out.
your right it must have been from a clogged riser.
I didnt know you need to replace risers.

thanks for your reply

I don't understand how you can change/modify the y pipe to anything different......
I'd like to see a pic if possible....
I apologize if I sounded harsh.....:redface:
Once the risers start to seriously scale, they will continue to do so & cause all sorts of problems, especially like you described.....

You can get new risers on ebay from Fredwarner1 for like $80 apiece....
They don't last forever in salt water......

Bondo · Sep 12, 2007

Re: melted tube alpha one

melted tube and a soft gasket that is also looking real bad the pump cover is blistered badly

Ayuh,........

It Sounds like it needs a Complete Water Pump Kit,.......
Including the Housings.........

coastalcruiser · Sep 12, 2007

Re: melted tube alpha one

Haut,
thanks again for the reply, one of the rules here is decribing everything correctly so i went to the manual i have and have a better idea what I'm talking about
I rewrote part of my last post
btw I have a 4 cylinder bell housing it's exhaust bellows looks different than the 8 cylinder one I used to have. Mechanic helped me replace it because my old one was shot. Wonder if that may be causing too much heat as i'm sure I could change it
Thanks. Rob

Haut Medoc · Sep 12, 2007

Re: melted tube alpha one

To my knowledge all bell housings are created equal on all alpha type drives 71-91, with the exception of the older style hinge pins with the keeper pins vs. the threaded ones with the trim senders on them....

I don't see how it would affect heat......
I'm still goin' with the bad riser theory....
Though a broken exhaust shutter lodged down there could potentially cause a 'hot spot'.....

coastalcruiser · Sep 12, 2007

Re: melted tube alpha one

Just got a new Mercruiser pump kit

that soft gasket was the old flapper I found restricting the exhaust flow and causing allot of extra heat
also I wanted to add that the manifolds and risers were my spare ones and were in good used condition, the rad guy said that they looked OK and cleaned up nice.
I took photos and will post them later, having trouble downloading them.
Thanks for your help,
Rob

coastalcruiser · Sep 12, 2007

Re: melted tube alpha one

Haut
I'm sure if i would have put new risers on in the first place this could have all been avoided.
Thanks

Bt Doctur · Sep 12, 2007

Re: melted tube alpha one

Once more:
When risers are cleaned the available cast iron is removed leaving the walls even thinner.Average life of a riser is 4-6 years.The telltale sign is a high speed overheat along with very warm feeling risers providing everything else is up -to-snuff. A test:
What cost`s more 1 a new engine
2 new risers

coastalcruiser · Sep 17, 2007

Re: melted tube alpha one

well I removed the stuck flapper thinking that was causing the problem
Put in the new wp kit took the boat out and the temp went down below 140!then started climbing again! so slowed down went back to normal 140 stays there until you go faster it will hold until the boat starts to plane it can stay at 160 if you go a little faster but anymore and it just starts climbing
I think i'm going to pull the leg again and inspect the wp then try a pressure test on the copper tube that goes into the wp that will also tell me if the hose in the gimbal housing has a leak
ayah

Haut Medoc · Sep 17, 2007

Re: melted tube alpha one

Have you inpected the condition of the water pocket cover?.......

Time for the clear hose test on the water feed from the drive.....
Plumb in a clear hose & see how many bubbles you are getting as well as checking water flow.....

coastalcruiser · Sep 17, 2007

Re: melted tube alpha one

i'm draining the gear oil.
going to flush it from the top with water and see, then later test with a clear tube before the heat exchanger. "bad water pocket cover", is that the top of the copper tube that goes into the wp?
there are 4 stainless bolts that are supposed to be brittle, I touched the tube and its not tight so maybe it's leaking.

Haut Medoc · Sep 17, 2007

Re: melted tube alpha one

coastalcruiser said:
i'm draining the gear oil.
going to flush it from the top with water and see, then later test with a clear tube before the heat exchanger. "bad water pocket cover", is that the top of the copper tube that goes into the wp?
there are 4 stainless bolts that are supposed to be brittle, I touched the tube and its not tight so maybe it's leaking.

Yep, that is really not something ya want to mess with if ya can avoid it.....

Do the hose test & that will tell ya ......

coastalcruiser · Sep 17, 2007

Re: melted tube alpha one

Yes the gasket in the water pocket is leaking

Haut Medoc · Sep 17, 2007

Re: melted tube alpha one

Well I would pull the upper.....
Flip it over.....
& soak them bolts in Kroil for a day before even attempting to remove them......

I'd start a new thread for "Water pocket cover removal" or search the archives.....

coastalcruiser · Sep 17, 2007

Re: melted tube alpha one

Haut,
thanks good idea i'm soaking those ss bolts in Liquid wrench
never heard of Kroil but will google it
I searched the archives and. I'm going to either have a real good day tomorrow or a bad one

ziggy · Sep 17, 2007

Re: melted tube alpha one

ya might try heat too. i made the mistake of touchin them waterpocket cover bolts. i don't have a torch and snaped off two of them, but the third one that broke was startin to come free after i took it to a machinist, he had heat, but, the creaton on the wrench kept turning it and snaped it. it might a come out workin it back and forth like a tap......maybe.......i ended up with 4 helicoils.....

good luck....

coastalcruiser · Sep 18, 2007

Re: melted tube alpha one

the 4 bolts came loose!
and the waterpocket cover is blistered
going to get perfect seal for the new bolts that don s recomended on another thread

ahhhh

melted tube alpha one

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