1975 Mercury 20hp Carburetor rebuild Will it run again or not? Let's dig in and see if we can fix

In this episode we have a dirty carburetor and possibly other issues. This is my story on the 20 hp Mercury.
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DEWALT 20V Max Cordless Drill Combo Kit, 2-Tool
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Engine Cylinder Compression Tester Kit
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Autolite Box of 4 Genuine 403 Copper Resistor Spark Plugs
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Quicksilver 866340Q03 Oil Filter amzn.to/3kWEPyq
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Video equipment used
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email me at
[e-mail]
mail me at
RMD Creations
PO Box 387
Wellman, IA 52356

[@Casen85]

Gotta be honest you helped me a lot with my mercury.

[@Notanotherfishingchannel19]

Oh and to add to that last comment--I would love to see this thing run under pressure in the water. Can’t wait to see the next video.

[@Michaelsbackyardmarina]

I ran it in a video, hope you saw it, thanks for watching

[@chrisb8127]

Great video as always! Ill be watching your 9.5 Johnson videos again and again! I have a Johnson 9.5 sea horse model #9R-73B that came with the boat a friend of family gave me. Its my first boat to restore \ build! All these videos help! It sat in the woods for about 10 years so everything needs to be rebuilt or replaced! The kill switch and the wires to coils are all rotten and broken, needs carb and fuel pump rebuild and the lower is leaking oil. And to top it off a carpenter bee got inside through the pee port and tore almost all the foam from the hood of motor and built a nest down inside the motor! I've never worked on an outboard before so I know this is gonna be a real fun job for me or somebody else if I feel like I can't do it myself here in the future! Wish I knew someone around my area like youself to help me out with this project!

[@Michaelsbackyardmarina]

There are tons of videos out there to help you move your project forward.

[@timconklin8489]

Great job can’t wait to see it running fully Thanks Tim

[@Michaelsbackyardmarina]

You and me both!

[@ricksnowden8408]

Restoring 73 20hp as we watch, great tip for the kill switch!!

[@Michaelsbackyardmarina]

Thanks and Thanks for watching

[@jrmrencso8716]

Good video Michael, I always assemble carbs with petroleum jelly, that way a dry screw won't tear a gasket or rubber diaphragm.

[@Michaelsbackyardmarina]

I like that tip. Thanks for watching

[@DocVogli]

Great Video, helped me a lot! One question i still have, did you put in the fuel pump both of that thiny gaskets? I mean that black and that "yellow" one. Because i have put from the carb site: 1. Thick gasket 2. Yellow gasket 3. Black gasket. And Motor is running...🤔 Thanks and regards from Finland Volker

[@anthonylatronica5108]

Nice job Mike

[@Michaelsbackyardmarina]

Thank you and thanks for watching

[@averagemodeler]

The video i have been waiting for. This will help so much on my motor.

[@Michaelsbackyardmarina]

Glad I could help

[@chriseisele9969]

Michael great work cant wait to see the mercury run in tank Chris from OHIO

[@Michaelsbackyardmarina]

The tank and then the water for sure will be fun.

[@codylambert8331]

I've got a 1975 Mercury model 110 9.8 good spark good compression rebuilt the carb it does a couple times then died. It's leaking fuel out the throat of the carb, did a pressure check and there's air leaking out the float needle, would that cause the leaking if the float needle doesn't close?

[@Notanotherfishingchannel19]

Love the video!! I have the exact same motor I’ve been messing with for over a year now and I have to stay on the primer bulb every so often. I’m assuming I have an air leak somewhere causing the mechanical pump to not have enough pressure to fill the bowl, or I possibly didn’t set the float to the correct height. I’m just taking it slow working on it but this video was so helpful I appreciate the time you took on it! I’m new to working on outboards so this video is my biggest learning experience yet. Thank you.

[@Michaelsbackyardmarina]

Awesome, thanks for watching

[@ludvigdahlberg6982]

Hi! I just picked up one of those old 20 hp mercs. I checked the spark with my tester and there was nothing. Then i took the plugs out and tested against the block. Still no spark. Then the first thing i did was to check your channel. when i checked my plugs i had the normal plug with a litle hook where the spark has to jup a litle gap. I see that your plug just have a dot in the middle. I wonder if that is why i have no spark. What plugs do you run and where can i order them? Hopfully that is the issue. Sorry if I am bad at english im watching al the way from Sweden. Love your videos by the way.

[@randythomas2512]

michel you do great videos

[@Michaelsbackyardmarina]

Glad you like them! Thank you so much for watching

[@johnmccrea8106]

Great job !!!

[@Michaelsbackyardmarina]

Thank you! Cheers! and thanks for watching

[@gustavhogberg6171]

So, the Butterfly Valve, how did you put it back? I am struggeling here 😩

[@richardcranium5839]

when you had the other carb i remembered something. i was always under the impression that the differences between a 9.9 and a 15 was the carb throttle plate size. sometimes it is but sometimes like i found on my 4 stroke is its the actual casting thats in the middle of the throat that makes the venturi. the 15 is about 1/8 inch bigger diameter is all.

[@Michaelsbackyardmarina]

Yes sir. Thanks for watching and being a regular commenter.

[@JamesWhite-tg4kw]

You just put the gasket numbers out there in our face but you don't know if it's the right ones lmfao 🤣

[@billrae4198]

I have the same motor- 74" pushes my 500lb 14' smoker craft @ 25 mph w/just me in it { I weigh 190} and gear- I did the same-rebuilt carb and resealed lower- bearing carrierO-ring gasget and prop shaft seals and I built a jack plate to dial in the cavitaion plate to skim the surface on plane- W/ 9x9 prop which seems to be just right rpm

[@Michaelsbackyardmarina]

Good to know. I can't wait to see what it does on my test boat.

[@dfoote22]

i tried clear fuel lines last year and it helped me see that i was getting air in the line from the fuel tank fitting, however, the clear fuel line didn't last a whole year. Over the winter i keep my outboard in the basement and when i got it out this spring the clear lines were hard as a rock and seeping air at almost every fitting. I wont use them again.

[@Michaelsbackyardmarina]

Were they fuel rated?

[@andrewwalizer8525]

Where can I get a new float at for mine?

[@macsorfi5815]

Michael I have the same 20 hp Mercury 1975…. question…. Tried to replace the impeller and the low unit still locked after a loose Two bolts. What else I need to loose?…. can you do a step by step youtube video about it?…

[@Michaelsbackyardmarina]

do a quick you tube search on Mercury 20hp water pump replacement, I'm sure you will see what you are missing. Thanks for watching

[@richardcranium5839]

i got tired of tough carb jets because the wedge shaped screwdrivers just dont fit right. briggs and stratton part numbers 19061 and 19062 have fit everything so far. also some of the bits that are in exchangeable but sets are round cut and have a nice square tip instead of a wedge.

[@Michaelsbackyardmarina]

Thanks for the tip, much appreciated. Thanks for watching

[@brendanklostermann4]

I’m not super familiar with carb engines or marine engines in general. But how would I go about adjusting my carb on this motor? I rebuilt it and it runs but it’s not happy, I’m assuming my tune is off

[@Michaelsbackyardmarina]

If I remember correct, there is only one air mixture screw on that carb, about 1 1/2 turns from bottomed out is a good starting point. thanks for watching

[@dougreno1151]

BA2E804 carb does not have a spring under the long needle,is that correct?thanks

[@Michaelsbackyardmarina]

That I am not sure of, thanks for asking and watching

[@robprepp]

My filter basket broke 😢 removing the carb

[@karvtek]

7:43 did you ever get that screw out? I can’t get mine out on my 9.8hp. Carbs are close to identical.

[@Michaelsbackyardmarina]

I did not, but the motor runs pretty good other than a strange sound I can not identify.

[@karvtek]

@@Michaelsbackyardmarina I guess I’ll leave it. I’m waiting on gaskets and compression tester. It won’t kick even if I put fuel in the carb.

[@supercrew63]

just did the w/p impellor and carb rebuild on my 77 35 johnson and seem to have a warm water leak under the hood runs perfect can't see where its coming from. any ideas

[@Michaelsbackyardmarina]

follow the pee tube. They can get brittle and crack and leak. Thanks for watching

[@Bryan-cr5kd]

I have a 25 hp merc im having problems with. Took the carb apart and the butterfly valve is jammed about 25% open. Any advice on getting it back in and moving freely? I have removed it now and am soaking everything in some parts cleaner

[@Michaelsbackyardmarina]

soak it like your are doing and take it easy is the only advice I have.

[@robertmindrup5315]

Light heat will break that jet loose & tap the scewdriver.

[@hammer9856]

Add a fourth thing to your list of what you have to have for an engine to run... Compression, spark, fuel.... and AIR.

[@Michaelsbackyardmarina]

LOL yep you need air. Thanks for watching

[@richardcranium5839]

tip when blowing out a computer hold the fans so they dont rotate. its too easy to overspeed them and trash the bearings. ask me how i know.

[@Michaelsbackyardmarina]

I'm with you on that. Thanks for the tips and watching

[@ozdatman]

So what I've learned from this video series is, if your going to buy an older motor get a Johnson.

[@Michaelsbackyardmarina]

Absolutely, thanks for watching

[@ricksnowden8408]

If the truth was known these old motors probably put a minimum of 30hp to the prop!!

[@Michaelsbackyardmarina]

I can't wait to see how fast it will push the 14' Sea Nymph. Thanks for watching