Fixing Old Mercury 110 9.8HP Outboard Engine

Hey guys! Today I'm going to attempt to fix my mercury 9.8 HP outboard boat engine. I've already unseized the engine by letting the cylinders soak in two stroke oil for about a month and then I broke them loose by the flywheel. I'll be changing the spark plugs in this video and I will also be rebuilding the fuel pump for the motor. I also cleaned the carburetor on the engine. I changed the water pump impeller and gear oil off camera but I hope you enjoy this video! I'm super excited to use this motor in the summer. If you have any questions leave them in the comments bellow!

[@scottmacpherson2352]

I just fixed the same one I had carburetor problems cleaned it up new impeller working great now.

[@tom_sassen]

Nice!

[@Devo1987]

Do you have a manual by chance for this motor ? ​@@tom_sassen

[@donny2handz731]

I just got the same engine and I haven’t gone through it yet. I plan to this week but the person that sold it to me said they were having trouble getting it started but when they did, it would run OK but then bog out they said that they were having to spray gas into the carb throat so they assume That it’s a carb float hopefully in the next week or so I’ll get it taken apart great video btw

[@scottmacpherson2352]

It could be your fuel pump to more them likely if you put in a new carburetor kit..

[@PlayingWithFireOutdoors]

Just fired up my long leg, after 3 yrs hibernation! It just runs great, I will be using it on a 3.2 m inflatable.

[@tom_sassen]

Right on!

[@tom_sassen]

@@The_Professional_American I think it's 18" as well but not sure

[@johannespaakkinen8359]

Sup man, i have an identical outboard and I’m having some troubles with finding parts. So I have two questions. 1 where did you find the blue print for it? And 2 where did you find those spark plugs? Loved the video btw 👍😁

[@georgechavez8002]

Thanks for your video… mind posting the part number to the rebuilt kit used.

[@tom_sassen]

Thanks for watching! I don’t remember the part number but I’m pretty sure I show it somewhere in the videos

[@michaelstarr5861]

I just got a Thunderbolt. Holy bjeezus, it's fast. Before 1985 Carl K. from mercury under-rated his outboards so they would out-sell the other brands. Then the government changed the dyno testing regulations in '84 or '85. So the '9.8' Thunderbolt dynos at least 12 hp.

[@tom_sassen]

Oh yeah they sure rip

[@travelguy1564]

What about the 7.5 Thunderbolt? I have a 1975 model. How many horse would you say it is?

[@tom_sassen]

9.9 I'm pretty sure or 9.5@@travelguy1564

[@Meirele]

Loved it!

[@tom_sassen]

Thanks!

[@kwonsfamily6648]

Great job! I have same issue on carburetor so need parts. where did you order the parts? Thanks for sharing

[@tom_sassen]

I believe off Amazon!

[@mb_swimmer2988]

Hey I have the exact same engine and was wondering where did you buy the rebuild kit from

[@tom_sassen]

I got mine from a marina but you can buy off amazon

[@garysmith5795]

So a word of advice to you...NEVER EVER spray starting fluid of ANY brand into ANY 2 stroke engine EVER. That's the best way to wash out any cylinder oil and cause piston/cylinder wall scoring! Especially since you just loosened up that engine from being seized. Instead...mix up some oil/gas mix and use a spray bottle to shoot some into the card directly that way these is still lubricant going thru the motor. And if you think the plugs are too wet to fire, pull them out and spray some carb/parts cleaner on them and reinstall. You're way better off doing it this way... Just some friendly advice.

[@tom_sassen]

Thanks for the advice! I was recommended that after I made the video but I will start doing that now that I know. I was using carb cleaner instead of starting fluid but I will use 2 stroke gas mix next time thank you

[@PlayingWithFireOutdoors]

My Arctic cat 900 cc doesn't like to start cold and they don't have a primer. So to prime it I use my premixed Ethanol free, very definitely a good idea.

[@garysmith5795]

@@PlayingWithFireOutdoors Smart man! Your cylinder bores will thank you for it....

[@scottmacpherson2352]

I had my friend he sprayed it every time with starting spray. Engine didn't last long 😅

[@piotr5369]

Hello, did you put two of the same seals (valves) or one? If so, which one - black or light? Regards

[@tom_sassen]

I put both on if I remember correctly

[@piotr5369]

​@@tom_sassenLooking from the fuel pump side, which one comes first? The soft black one or the harder light one?

[@tom_sassen]

I don’t remember, if you watch the video closely I show a diagram of the fuel pump

[@piotr5369]

​@@tom_sassenWhere did you get the carburetor diagram from? 

[@tom_sassen]

Just online I think@@piotr5369

[@MarvsFixitShop]

Nice job

[@tom_sassen]

Thank you

[@piotr5369]

Hello, what is the maximum speed of this engine? Regards

[@tom_sassen]

Depends on the size of the boat. Probably like 20-30km|h

[@daddski1]

gasket number 6 and number 21 are needed as well as 20. if you look at the bottom center they have two nipples kinda. these actually help pump fuel into and stop fuel from backing out. ther number twenty is a pass through without the flappers. there are manuals online or find a merc or clymer manual. if the gaskets were there before thewn they need to stay there.

[@tom_sassen]

Yep! It pumps properly that way

[@piotr5369]

What year is this engine??

[@tom_sassen]

I believe it’s in the 80’s

[@markkmiecik9797]

Don't know if you noticed, but it's not pumping any water in the beginning.

[@tom_sassen]

Yeah it pumps good water now though. Changed the impeller

[@tom_sassen]

Let me know if you guys have any questions on fixing this motor!

[@jamessinclair3278]

Just bought one of these engines, been told it turns over an thats it, bought it blind and should be delivered early next week so I may be I touch 😂 nice vid tho ma man

[@MarvsFixitShop]

I’m working on a 20HP now and it’s really giving me issues

[@tom_sassen]

Nice!

[@Clayton_reagan22]

I’ve got one like it it was my great grandpa‘s I’m gonna see if I can’t get it running😂

[@tom_sassen]

Do it! It’s actually a lot easier to work on than I thought and you still can find parts for it

[@derekbeck6204]

I have the same engine and I am searching for a part or part number, hopefully someone can help. The smaller hose from the carburetor goes back into the engine through an elbow. The elbow is brass and I believe it is a 3/8" threaded male on one end and an 1/8" id hose barb on the other, and also has a built in screen. I broke the damaged hose barb completely off. Does anyone know where I can get that elbow?. Thanks

[@tom_sassen]

Did you look on boat parts . net?

[@JAllen-db2kv]

Are you sure you are supposed to stack those gaskets? I "think" they are showing 3 gasket options in that position for different situations. I don't think you are supposed to use all of them. I've never heard of stacking gaskets before.

[@tom_sassen]

I’m not sure either but they did it in other KZbin videos I’m pretty sure. And it runs pretty good so I’m guessing it’s ok but we’ll see what happens

[@daddski1]

youabsoolutely are supposed to stack fuel pump gaskets. been building these things for 54 years now... sadly was building this when it was new lol

[@virgilfoster5270]

🙄 Promo-SM

[@Doublejj55]

Um it’s a 2 stroke my man

[@tom_sassen]

Yes? Did I say it was a 4 stroke?

[@bradcoons6336]

I am looking for a replacement carb for my 9.8. The guy who owned it before me had over-tightened the mount bolts and cracked the base of the carb. Anybody know where I can get one? Mine is a 1973 Mercury 110, 9.8 hp.