Melted water pocket tube

[Ffranzwa]

Hey everyone;
I'm replacing the gimbals, u-joints, and waterpumps on my '88 Chaparral w/ twin 350's (260).
On the starboard outdrive, the water pocket tube on the upper housing has melted and the cover is bubbled like it has been hot. The water pump housing on the lower unit also had bubbling. I've replaced the old pump with a new one and I'm assuming I'm going to have to replace the water tube and the cover bolted onto the upper housing. Does anyone know why this occurred and how it can be prevented in the future?
Thanks,
Fred

 

[Fishermark]

Re: Melted water pocket tube

I'm assuming I'm going to have to replace the water tube and the cover bolted onto the upper housing.

Hi Fred! Welcome aboard!

Now for the bad news - from all accounts, the upper cover tends to be difficult at best to remove. BE CAREFUL NOT TO BREAK THE BOLTS that hold the cover on. If they break you are basically out of luck.

Does anyone know why this occurred and how it can be prevented in the future?
Thanks,
Fred

Too much heat / not enough water flow.

 

[ziggy]

Re: Melted water pocket tube

Does anyone know why this occurred and how it can be prevented in the future?

my guess would be the impeller in the water pump disintegrated due to running w/o water being supplied to it.
it only takes a few sec. of running w/o water for the degradation to start occurring. within a min. and a half of running w/o water supply the impeller will likely not have any vanes left at all. alpha1 impellers are fragile imho. mine gets replaced yearly in my one drive which takes the same impeller as an alpha1.

the plastic guide tube that melted will come with the new water pump service kit. so that's no big deal.
the water pocket cover however may be a big deal.
i've had a severe overheat. what i stated above occurred to me. you need to remove the tstat and hopefully find impeller pieces there. i removed the lower only on my boat. also i then removed the feed hose from the transom up to the tstat. i flushed water both directions into a bucket till i got no more fragments. while i was flushing ft. to back. i noted the seal on my water pocket cover was leaking. this is bad. i needed to replace the cover. there are 4ea. 1/4-20 ss bolts that hold it on. these bolt will just snap right off.. be as careful as you can be when removing them. i've heard of folks getting them out. myself, i snapped off 3. 40hrs later of drilling the ss studs out i was able to helicoil the holes. if i would have been unsuccessful. i would have had to replace the upper.

like i said, be careful removing them bolts. you'll be sorry if you break one or three. i believe the reason the break off is the dis similar metals of ss and cast aluminum naturally cause them to corrode in place.

good luck.

 

[Ffranzwa]

Re: Melted water pocket tube

According to my temperature guages, the engines have always run cool until they idle for awhile. Increasing the rpm drops the temps almost immediately.
It sounds like the bolts attaching the water pocket cover are probably not going to come out clean. Can I simply replace the tube and leave the old, blistered cover in place?
Thanks for the advice!
Fred

 

[Don S]

Re: Melted water pocket tube

I simply replace the tube and leave the old, blistered cover in place?

If it's not warped, and doesn't have holes in it, and the rubber seal is replaced in the end, it MAY be ok. Block of the water passage and fill the tube full of water and see if it leaks out. If not, you should be good.
But I would replace the raw water pump housings, check the exhaust flappers, and chect to see if the risers or manifolds water passages are plugged up.

 

[ziggy]

Re: Melted water pocket tube

Block of the water passage and fill the tube full of water and see if it leaks out.

that sounds like a good idea. the way i knew mine was leaking was when i was flushing impeller pieces out from ft to back. i could see the water was leaking out of the seal of the cover. and there was no restriction at that point either. just an open tube with water flowing though it, under pressure (garden hose) of course.

and leave the old, blistered cover in place?

if it is leaking, i'd think it would need to be addressed. the way i understand it. if it leaks. there are hot exhaust water flowing by the cover. this hot exhaust water can be introduced into the cooling water via the seal leak and cause over heat issues... so it is important to have the seal in place. that's the way i understand it anyways..

 

[havasuboatman]

Re: Melted water pocket tube

According to my temperature guages, the engines have always run cool until they idle for awhile. Increasing the rpm drops the temps almost immediately.

An engine that starts to get warm at idle but cools with a little throttle is indicitive of low water voluum from the fresh water pump. That can be from blockage, worn out impeller, or impeller housing.

 

[sarantis]

Re: Melted water pocket tube

When i baught my Sea Ray at first check of the outdrive i found exactly what you describe.The previous owner had told me that the engine had been overheated due to worn out impeller.I can't imagine howelse these things could melt.At low rpm the most of the outdrive is in the sea water which i think it would prevent the plastics from melting.The water pocket removal also was a nightmare with all 4 bolts broken so i would suggest to leave it as it is unless you see an obvious leaking.But most important since your boat and outdrive is out ,is (what Don S suggests)to check the flappers at the Y-pipe even if this means removal of the engine. I 've paid a lot for a check that didn't cost anything

 

[havasuboatman]

Re: Melted water pocket tube

What melts (or bubbles) the pieces you mention is the uncooled exhaust gasses. Happens really fast when you run a boat out of water with no hose hooked up. When the exhaust enters the drive, it is directed right onto those parts.