1988 Aphla One V-6 Overheated

[gunpacker]

Hey Guys,
Just found this site & joined.
I have a 1988 23 ft. walk-around w/ aphla one v-6 and I'm having overheating problems.
Took it out last month and after about a 1/4 mile down river it started overheating, steam from out of the water, temp gauge was max. out. I shut her down and let it cool. I have a trolling motor on it so I was able to get back to the docks using that. Talked to my marine repair shop & he said that it showed like the inpeller so I had him put a new kit in it and he teast run it. said everything was working fine.
This last weekend take it to the river again & I'll be damned if it did do the same thing again, made about to the same spot as last month. This time no steam, but it was red lined on the gauge & I pulled the engine cover and you could see that the gasket between the manifold & the thermastat housing was sizzling so hot you could have fried bacon on it. So let it set all afternoon to cool down. thought ok I could fire it up and make it back to the docks. Well it made it within about 100 yds of the docks when the radiator cap blow & the motor couched a couple times and died. It blow steam & water all over the place. So, my question is thermastat, water pump or inpeller again or just replace all the three? do you think just off the top of your head that any damage has been done to the motor.. Oh, forgot to tell you this is a closed coolant system.

Thanks guys,,

 

[rod_stewart]

It sounds like your heat exchanger is not getting cooling water, or may be completely plugged off.

Here is my overheating guidelines just for reference:
It is mainly for raw water cooled applications, but much is the same for closed cooling systems.

[h=1]Overheating Problems (Alpha Drive Leg)
[/h]Be sure you have enough water going to the muffs, don’t be shy with the water. There should always be excess water spraying out the sides of the muffs, thereby indicating that there is more water than the pump can pump. Do not rev the engine up while on muffs; you could suck the hose flat and cut off water flow entirely. Not good. 1500 RPM is the recommended maximum.

By the way, you cannot overpressure your cooling system running on a hose with conventional muffs, as some sources would suggest. The spring in the muffs acts like an overpressure relief valve and limits the pressure at the pump suction to about 1.5 psig, or about 40 inches WC. There is no way this will hurt anything.

To check pump flow, temporarily unhook the water inlet hose (coming from the drive leg) at the T’stat housing and hold the end in a bucket, and time the water flow while a helper briefly idles the engine at 1000 RPM.

An I-4 (1.94 drive) water pump should put out 3.5 gallons a minute at 1000 RPM.
A V-6 (1.81 drive) water pump should put out 4 gallons a minute at 1000 RPM.
A V-8 (1.47 drive) water pump should put out 5 gallons a minute at 1000 RPM.
All should be able to fill a standard 2 gallon plastic bucket in 30 seconds or less.
If not, something is not right.
If there are apparent air bubbles in the water, the pump is sucking air. This indicates a damaged impeller.

Here is a list of the usual overheating suspects:
-pump impeller and/or housing bad; insufficient water flow. Service pump.
-leaky impeller or housing allowing air to be sucked into water stream
-leaking water pump to water pipe coupler; coupler not fully sealed
-faulty water pocket or water pocket seal
-foreign object in inlet hose or T’stat housing (such as impeller pieces)
-kinked hose between drive leg and transom assembly
-collapsed, blocked or kinked hose, blocked PS or oil cooler, etc
-T'stat stuck, partially plugged, or missing
-bad circulation pump or belt
-plugged exhaust manifolds or risers
-plugged check balls in T fitting lines to risers (where equipped)
-salt and/or corrosion encrustation or other blockage in block, heads, manifolds, risers, hoses, or heat exchanger (if equipped)
-dirty or leaking heat exchanger (where equipped). Flush/brush out the tubes.
-bad exhaust flapper causing higher pressure in one riser than the other causing unbalanced discharge water flow.


The very first thing I would do is check water flow at the hose that enters the heat exchanger raw water side.


Rod