# 1975?? Mercury 200-20hp



## baseball_guy_99 (Apr 15, 2011)

As mentioned in my rebuild thread, my uncle gave me an older mercury 20hp motor. Well since the boat rebuild is done I decided I would like to tackle this bad boy and get it running again. It was originally a tiller handle but was converted to controls.

The only serial number I can find is on the front of the motor where the steering bar would be. The number is 4103884. From what I can conclude that would make it a 1975?

If anyone can give me any information on this motor that would be wonderful. Like replacement parts or maybe a manual 


I will get some pictures up ASAP.


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## baseball_guy_99 (Apr 15, 2011)

Here are some pics...i can get more upon request.


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## baseball_guy_99 (Apr 18, 2011)

So I got to do alot of tinkering on it today.

Pulled the top off that houses the recoil starter and greased it up really good. Now the rope will recoil on its own.

I pulled the spark plugs out and turned the flywheel by hand. It's not locked up!!! It was a little hard turning so I made up a mixture of sea foam/gas/oil. squirted some in and turned it several times. This loosened up the pistons a whole lot. 

I then checked to see if the spark plugs were getting spark...they were. So I squirted a little more of the mixture in and gave her a tug...nothing. Pulled the choke out a bit and pulled...still nothing. So I pushed the choke back in and gave another tug...it fired!!! (I quickly shut it off)

I went and got the water hose and the muffs to see if she would start and run. I squirted a bit more of the mixture in and it started up and ran for about 5 seconds but I noticed it was not peeing water so I shut if off (new water pump will be put on).

I then tackled the carb. I pulled it off and disassembled it. Boy was it varnished like no other! So I took the bowl and soaked it in some carb cleaner, that took the varnish right out of the bowl. The float is still in good condition so I cleaned it up a bit. I took the jet out and sprayed some carb cleaner down it and some down the throat of the carb. I then hooked up the air compressor and sprayed everything out.


My next task will be to change the water pump and the lower unit oil. So far the only think i can think that it needs is a tiller handle. So if anyone knows what years are compatible with this please let me know. Also if the 9.8 110 (I think they are 110 models) are compatible.

Thanks in advance,
Donnie


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## crazymanme2 (Apr 19, 2011)

Did you pull a compression test :?: 

I have 2 of that vintage motor.Both a 1979.I know that Merc has a couple different electronics set ups for the mid 1970's,but I think most of the external parts are the same.

I'm not sure if the 110 is compatible.


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## baseball_guy_99 (Apr 21, 2011)

I didn't do a compression test, but it seems to have good compression. Is there any way to tell without getting an actual compression tester...I'm workin on a budget here (so unless that tool is like $5 then I'm SOL)

More updates...

I went to my dad's house to get the repair manual for this thing and he gave me some lower unit oil that he had left over (yay money saved there!)

So after cleaning up from the storm last night, I decided to tear into the lower unit. I'm glad I had the manual because without it, I would probably still be sitting there staring at the motor trying to figure out how to take the lower unit off. I pulled the lower unit off and it was full of mud daubers nests! So I got them all cleaned out.

I then changed the lower unit oil. The old stuff that came out seemed pretty clean. No water and no metal shavings. So i drained it out and put the new oil in.

Next came the water pump. I opened it up and surprise, surprise...more nests. I took the old impeller off because it was pretty worn down and 1 of the splines was cracked. I cleaned up the inside of the water pump and put new gaskets and the new impeller in. Got it all back together and got the lower unit back on the motor......I then realized I forgot a bolt. So I had to take it all back apart to put the bolt where it needed to go. Got it all put back together right this time. 

Then I reassembled the top of the motor and put the carb back on. I replaced some fuel line and the fuel connectors.



Now for the test...I put the muffs on the motor and turned the water on, climbed in the boat and gave some tugs. It wouldn't start. So i grabbed my mixture of stuff and squirted some down into the cylinders. Climbed back into the boat and gave it a tug...started and ran for about 2 seconds. So now I will go through and rebuild the fuel pump. I bought a gasket kit for the fuel pump and carb. That will be my morning project.


Sorry for no more picture updates, I just got wrapped up in things and forgot to get my camera.



I put of budget of $150 on this project. So far I have spent $55

Fuel pump and carb kit-----18
Impeller and gaskets-------22
Fuel line-------------------2
Fuel Connectors-----------9
Hose Clamps---------------4


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## crazymanme2 (Apr 21, 2011)

There are auto parts stores by me that will let you use a compression tester.Maybe have to leave a deposit that will be fully refunded when tester is brought back.

It sounds like your on the right track.

I like to know what compression is so I don't spend money on a motor that needs rebuilding.Not saying your does.


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## baseball_guy_99 (Apr 22, 2011)

It's all good in the neighborhood!!!


I pulled the carb and fuel pump off this morning. I gave the carb another thorough cleaning in case some debris had made its way into it.

Then I tackled the fuel pump...pulled it apart and I can imagine why it would not pump any fuel...The cork gasket that goes between the inlet piece and the main body of the fuel pump was just disintegrated and all gummed up in the filter. I got it all cleaned out and replaced that gasket with a new one. Then I pulled the diaphragm and gaskets out of the fuel pump and they were hard as a rock. I cleaned off the metal parts of the fuel pump because they were caked with varnish and little pieces of the gaskets. Then I reassembled the fuel pump.

I put the whole thing back together and replaced the fuel line and water line for the tell tale. 

I then hooked up the garden hose and pull the rope...it started up on the 2nd pull and stayed running!!!! It had a good healthy stream of water coming out of the pee hole. I opened up the throttle a little and it had no hesitation what soever.

So now all that's left to do is get a tiller arm for it!!


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## baseball_guy_99 (Apr 22, 2011)

https://www.youtube.com/watch?v=C_XefqbQpH8


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## dwgarner (Apr 10, 2012)

Where did you get your parts from? I have an identical motor and have not found the kits cheaper than like $60.

Thanks,
Danny


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## baseball_guy_99 (Apr 10, 2012)

I don't remember exactly where I bought them from. It was either eBay or boats.net.


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## Gramps50 (Apr 10, 2012)

I have the same motor except that it's a 1971. Mine was on my boat when I bought it. The wiring was old and the installation was falling off so I rewired it. Now I'm rebuilding the water pump and replacing the shift shaft seal. 

I searched around and found a parts list which I found out today actually came from Mercury Marine as it was the same one the parts man at the dealer was using. I have a service manual that that covers serveral different motors, its better than nothing. Most of what I have I downloaded for free and a couple I paid a small fee to download. Don't remember where I found them, not much help I know.


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## spacks013 (Apr 27, 2012)

Nice motor. I have a '73, looks to be the same. Don't buy the Clymer (sp?) book on this thing, it sucks. For a motor that seems pretty common, there is not a lot of info out there. Did you find a tiller for it? I have seen a few on ebay lately. I would suggest, if I may, that you keep the prop in the garage or indoors in the winter if you live in a cold climate. I have spun a few out, seems like the freeze/thaw thing may have an effect on them.


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## baseball_guy_99 (Apr 27, 2012)

I did find a tiller on eBay...in total I put $135 in the motor and I sold it last fall for $600


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