1982 Mercury 9.8 Coolant Passage Blockage

[scout-j-m]

I picked up the subject motor late last summer for really cheap. Figured I'd fix it or strip it and sell the good parts. Luckily it had great compression but the CDI box was shot. I waited probably 3-4 months for the by far cheapest one online to get back in stock and got it installed and now have excellent spark. I lightly cleaned the carb and replaced the impeller and the little 9.8 fired right up. However, nothing came from the pisser nor any other exhaust location above the water line in the barrel I ran it in. Got my IR thermometer and restarted it and the temp on head was getting crazy hot so I shut it down and pulled the lower unit. Submerged the lower in a bucket and put the driveshaft in the chuck of my drill and was able to verify that the water pump was working great. I blew compressed air both up the water tube and back into the pisser fitting on the block/head. When blown into the head the air was exiting the exhaust through the leg but when blown up the water tube it felt and sounded almost completely plugged. I assume there is a rubber grommet of some sorts where the water tube meets the powerhead. I also assume I have to pull the powerhead to replace. Am I on the right path here? Is it relatively easy to pull the powerhead on these model motors? It looks pretty simple but this is my first time working on this model.

 

[racerone]

There is a plastic washer at the TOP of the water tube.----I have seen countless of these melted and blocking flow to the motor.-----Factory replacement is a better material.-----Powerhead is easy to remove to inspect this

 

[scout-j-m]

There is a plastic washer at the TOP of the water tube.----I have seen countless of these melted and blocking flow to the motor.-----Factory replacement is a better material.-----Powerhead is easy to remove to inspect this

Thanks! I noticed the replacement washer almost looks like a fibrous, high temperature resistant material so good to hear it's an improvement. I'll get the washer, seal, and powerhead gasket ordered.

 

[Sea Rider]

If that motor was used in salt water, better remove the entire powerhead form base and remove the exhaust cover if having one and the cylinder head to mechanically clean all water passages, take advantage to decarbon piston heads along exhaust chamber. as well. Will need to order new base, exhaust Cover and cylinder head gaskets. Install a new thermostat and gasket.

This is what will find if the motor has been running on salt water...





Happy Boating

 

[scout-j-m]

If that motor was used in salt water, better remove the entire powerhead form base and remove the exhaust cover if having one and the cylinder head to mechanically clean all water passages, take advantage to decarbon piston heads along exhaust chamber. as well. Will need to order new base, exhaust Cover and cylinder head gaskets. Install a new thermostat and gasket.

This is what will find if the motor has been running on salt water...





Happy Boating

I don't think it has, but once I pull the powerhead I'll check it out and see.

 

[racerone]

???----Searaider,---- there is no cylinder head on this motor !!----There likely was no thermostat either when it left the factory.

 

[scout-j-m]

???----Searaider,---- there is no cylinder head on this motor !!----There likely was no thermostat either when it left the factory.

Good point. This one does not have a thermostat and has no head like you mention.

This brings up another question...since the powerhead water inlet is almost totally blocked due to melting and I have not ran it but a couple times in a barrel, it means it was overheated by a previous owner. Since there is no head what are the side effects of an overheat aside from seizure? It has always turned over smooth and has 120 psi on both cylinders. Could the melted water tube washer be the only damage done?

 

[racerone]

At this point have verified that this washer is damaged ?----And was water 6 or 8" above the pump in your test bucket ??

 

[Sea Rider]

Oops, so it's the closed sealed cylinder model. Better remove the powerhead from its base and mechanically clean all water passages located under the powerhead, check the water connector, grommet whichever that connects to the lower powerhead if needs to be replaced.

Happy Boating

 

[scout-j-m]

At this point have verified that this washer is damaged ?----And was water 6 or 8" above the pump in your test bucket ??

Yes, I had the water level to the point that the water tube adapter was just out of the water when I turned it with a drill and it worked well. When I tried the motor with the lower attached, I used a cut off 55 gal drum which had the water level about 12" above the water pump and 18" above the water inlet on the cav plate.

I will pull the powerhead tonight to make sure that the water tube washer is the issue. I'll post a pic of it for added clarity.

 

[Sea Rider]

If impeller is in excellent working condition, bolt back the lower leg, connect a power drill on drive shaft and check if water pees out well on pan, if so, the powerhead is clogged...

Happy Boating

 

[racerone]

Searaider----Post # 1 states that impeller was replaced.-------Did you read posts #2 and #3 on the next steps that were planned ??

 

[scout-j-m]

 

[scout-j-m]

The water tube washer was indeed melted. It was pretty much totally blocked.

I scraped most of the power head gasket off and put on some gasket remover to soak overnight. Once I get the surfaces cleaned I will blow air through the block passages to ensure there are no other obstructions before reinstalling the power head. This will give me a good chance to clean everything up as its really nasty in the lower cowling.

 

[racerone]

Fixin motors is childs play is it not !

 

[Sea Rider]

So no salt formations found ?

Happy Boating

 

[Faztbullet]

The picture show no build ups......don't thnk its near saltwater.

 

[scout-j-m]

So no salt formations found ?

Happy Boating

Nope. All just unburnt fuel/oil residue. I'm about 6 hours from the coast so I typically don't have to deal with corrosion issues...although I have on a few occasions.

 

[scout-j-m]

Totally forgot to update this.

I used a degreaser and cleaned up the lower cowling the best I could. I then reinstalled the powerhead with the new water grommet and a new gasket. Took a bit to get it started but when I did it was pumping water excellent and running nice and cool.

Discovered a few more issues, primarily that the coils are arcing and seem to be damaged. Spark is still strong though after I wrapped in electrical tape. Since the CDI was also bad I'm wondering if the motor overheated a few times and the heat damaged those components. I paid $100 for the motor which included a fair shape 6 gallon tank, paid $150 for a new CDI, and then about $40 in other small parts including a carb kit. Don't think I can justify buying new coils as I cant see this motor being worth too much more than $300 in my neck of the woods.

Appreciate the help guys.

 

[racerone]

Everybody looks at the economics in a different way.----That motor may well be better built than a new one today.-----If you need to spend time effort to find a few parts is easier than finding $3000 for a new motor.