Melted plastic guide tube between Alpha one halfs

Happy holidays all just finished fall striper season here in the Northeast. Finished the year with only one keeper, but what a nice fish. 50 inches 49 lbs! Anyhow pulled drive and split for inspection. First thing I saw was the 4 metal plates for exhaust flapper valves. Then I noticed white plastic guide tube all melted. My theory is flapper valves failed, fell to bottom and restricted exhaust water flow making exhaust too hot. Any one agree. Or am I on the wrong track. Thanks

What drive? Alpha 1 gen 1 or 2

WHat condition is the impeller? When was it last replaced?

Gen 2 SEI factory new spring 2013. haven't looked at impellor yet. Never saw any abnormal eng temps

First thing to ask is why did all the flappers come off?

If they see to much heat that can happen......

If only one or one half had come down then maybe your reasoning would be ok.

My thought is that maybe a lack of water exiting the elbows .......or maybe a lack of water flow at higher speeds.

HArd to say if your over all temps did not get higher than 170-180............

The newer gen 2 water pump impellers are pretty good and don't have the same failures as the gen 1 did......

But seeing as you have it apart why not look at the impeller and see if maybe it was damaged when sucking something up?

Was there steam?

yup will look at impellor tonight. Always seems to be steam, thought that was kind of normal. never see more than 160 degrees except one time a hose came off front of engine, temp got to top of guage. The thing is I caught it quick immediately shut down got hose on. Don't think it was up there more than 30 seconds. been running 160 ever since.

rl65028 said:

My theory is flapper valves failed, fell to bottom and restricted exhaust water flow making exhaust too hot. Any one agree. Or am I on the wrong track.

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I will agree with your theory in that the exhaust gases were too hot!

The A drive seawater pump is in the lower drive unit.
The tube coupler that you describe would carry the sea water up into the upper gear unit and eventually to the engine.

Lack of cooling water (spelled possible impeller pump failure) most likely caused dry exhaust heat!
Dry Exhaust Heat most likely damaged more than the parts that you have seen thus far!

I would suggest beginning at the seawater pump.
Examine and replace any parts forward from there, including the loop hose that runs from the Gimbal Bell to the Transom Housing unit.
Keep going until you are satisfied that all components are good.

Now remove your exhaust elbows and elbow-to-Y-pipe couplers, and inspect things from that point AFT.


.

The plastic tube is a guide for the copper water tube the connetcs the upper to the lower.
The gen II cooper tube has a bend in it and it is not easy to align.....


Also look at the upper where that copper tube goes to make sure there is nothing going on there.
Possible pinch...

Without knowing your cooling system layout/motor....i can comment on that.
But if a lack of water flows thru the elbows at idle or before the thermostat opens this could cook everything down stream.

So until you let us know what motor and year and serial number....cant do much from here..

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kghost said:

The plastic tube is a guide for the copper water tube the connetcs the upper to the lower.
The gen II cooper tube has a bend in it and it is not easy to align.....
I had forgotten about the bend, but I'm thinking that my comment would be the same.

Also look at the upper where that copper tube goes to make sure there is nothing going on there.
Possible pinch...
Good point!

Without knowing your cooling system layout/motor.... i can comment on that.
But if a lack of water flows thru the elbows at idle or before the thermostat opens this could cook everything down stream.
Stat open or not open.... the amount of seawater that is by-passing engine cooling demands would appear to be insufficient enough to have caused the hot exhaust gas damage to the plastic tube parts and the back flow prevention flappers.

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If you were up on plane, running, when the overheat happened, that's long enough for the reduced water flow to induce lots of damage....

except one time a hose came off front of engine, temp got to top of guage. The thing is I caught it quick immediately shut down got hose on.

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Ayuh,.... I'm with makomark, that's probably long enough to Smoke all the rubber, 'n plastic parts in the exhaust stream,....

The temp Gauge, don't even have to get Hot, so long as the water flow stopped, the exhaust temps would go from a wet 160° or so,...
To a very Dry, 1200°,....

SEI reports impellor was pretty normal. Im going with makomark theory. My other thought is clogged power steering cooler. Does anyone think that could do it? Any one know how to check it? Oh and KGhost asked what configuration: 5.7 with standard cooling system. Factory new engine from michigan motorz this year. Also the boat is re engined from a 4.3 to the 5.7. The drive was under warrenty from sei. They went through it fixed it up. Had them change ratio 1.84 to a 1.47

If you have a standard cooling (no heat exchanger) then there is one water hose coming from the transom that feeds the thermostat housing (fresh water supply). Somewhere along that hose is the power steering cooler. The incoming water hose connect to it. It is about the size of a standard 2 d cell flash light so to speak. Only a couple of hose clamps hold the hose ends on. remove both hose ends and flush with hose water towards the transom or back towards outdrive and see if anything comes out.

If all is good on the water pump impeller then I would also agree that the high/moderate speed run with the water hose falling off could have scalled your plastic tube.......

Thank You Kgost. That is exactly the configuration I have