some one please help-its drivin me mad

[rnli rich]

recently i aquired a 7.5 1980 ac lightening,upon testing it i found the tell tale to be spouting very hot water, upon advice (from here) i have changed the gaskets on the water jacket (tell tale exit block).and checked the thermometer ,now its not pumping at all, i have checked for blockages and none are found, what i have found however is that if i blow down the tell tale whilst the engine is in a bucket only a few bubbles show,however if i blow down the tell tale and cover the exhaust hole on the leg the ammount of bubbles increases,
which means in my crazy thoughts that somewhere exhaust is getting in with water and as the pressure from the exhaust is more that the water pressure,the exhaust wins.
some one please help me get this baby pumping water as it should again

 

[Xcusme]

Re: some one please help-its drivin me mad

Rich,
You will be well advised to drop the lower unit and repair-replace the water pump. If the water pump cup and wear plate look good, replace the impeller. Complete water pump assemblies are available too. Make sure the test tank is deep enough to fully submerge the lower unit and midsection above the water pump.
A service manual will guide you through the steps necessary to get the cooling system working..

 

[rnli rich]

Re: some one please help-its drivin me mad

thanks for your reply,i will take a look at the impellor housing etc and have my clymer manual at hand and am scouring it with great interset, however, before i changed the exhaust jacket gaskets etc, she was pumping water,i havent touch the lower leg so assume it is in the same good condition that it was before i changed said gaskets, if i find the impellor housing etc to be ok what other causes could be affecting it , i have taken a good visual look at the head and found no cracks or other deformaties

when i run the engine it seems as if the exhaust fumes are coming from where the tell tale water exit is-what would cause this

many thanks again for all your advice

rich

www.appledorelifeboat.org.uk

 

[Xcusme]

Re: some one please help-its drivin me mad

Rich, The key here is that you said the "Tell tale was spouting very hot water". This can point to a weak water pump. I see that you have a thermostat too. I think that thermostat is set for 143 degrees. You said you checked the thermostat, how??
I'm assuming the exhaust cover gasket install was done right, with no internal or external leaks.
If you start the motor in a test bucket with the thermostat removed , you should get water gushing out of the thermostat hole. This verifies that water pump is working. Again, the water level has to be above the water pump for it to work properly.

As for your air tests on the tell tale. I would expect more air bubbles from the prop area when you pressurize the tell tale line while blocking the exhaust idle relief vent. Water and exhaust should exit the idle exhaust vent while running.

You didn't mention how the motor was running. Have you done any compression tests for a possible head gasket leak? Inspect the plugs for signs of water intrusion , i.e. steam cleaned plugs or droplets of water on the plugs. I've seen a bad head gasket pressurize the water jacket and stop the flow of cooling water.

EDIT:

One last thought:

Please keep to ONE thread. You've opened 5 threads on your motor and it's gets really hard to follow what you've previously asked and answered.
With one thread, folks can see what you've done and can help you to resolve the problems. Thanks for helping us to help you.

 

[rnli rich]

Re: some one please help-its drivin me mad

thanks for all your help; finally after working most of the past two weeks i finally got to have a good go at sorting the problems, i took the lower leg off and totally cleaned it up and checked it was pumping water-it does,and very well, i now have found what i think is the problem, it seems that i have a blockage right up the water intake pipe ( the pipe running from the water pump up into the engine block), i have tried blowing up the pipe and down the pipe(from the water jaket) and using pressurized (garden hose) water up the pipe and down the pipe without any luck.
could someone please advise me of what to do next, i really dont want to take the whole thing apart as it seems i have to do in my service book (seems beyond my skills) to get to the blockage, i think its a piece of instant gasket that is stuck up their as that is what i found blocking the water pump up,
any help would be greatly appreciated

 

[tmcalavy]

Re: some one please help-its drivin me mad

I'm not familiar with your outboard, but with the older OMC's you can drop the lower unit and pull the water tube out and replace if necessary. Most are simple copper tubes that fit into rubber grommets at both ends. Use less sealer next time. It's a good idea to change the water pump impeller once a year or every other year...if you like the motor and want it to get you back to the ramp/dock.