Merc 110 starts and runs then dies after 30 seconds

Hi all,

This is my first post as my brother and I just bought a 1975 Jon Boat. We bought it for $400 it needs new paint and seats and carpet but other than that it seems pretty solid!

It came with 2 outboards, a 6hp evinrude and a Merc 110. as well as a trolling motor.

Couple questions, can both of these engines run off the same gas and oil mix? I have read 50:1 is the ratio? Also what is the best brand of oil?

The engine has been sitting for over a year and while this is our first boat I am mechanically inclined, at this point I am thinking of changing the impeller and lower unit oil and checking the spark plugs and cleaning the carb and hitting it with a can of seafoam.

Please counsel me if any of this a bad idea lol. Also when changing out the oil in the lower unit I have watch a couple videos and it shows them filling it from the bottom till it comes out the top, is there some reason behind this? Why can you just plug the bottom and fill from the top? Also what is a good gear oil?

Sorry for all the questions! All help is much appreciated!

Also if you guys can help with the year and where to find parts for the engine that would be great!

Post the serial numbers of both. Fill leg from bottom to avoid air filled voids. 50/1 will be good for both although I have a 2hp Evinrude that is 100/1. All your ideas are good although it is possible neither the impeller or oil need changing. Doesn't hurt to look though. I use Lucas SAE80W-90 Heavy Duty gear oil in my legs.https://www.leeroysramblings.com/ will give you lots of good info on your motors.

IMO any outboard brand of 2 stroke oil will be fine, they will run off the same tank but I don't think the same hose hook-up will work, the connection is different I'm quite sure.

Crazyboat said:

IMO any outboard brand of 2 stroke oil will be fine, they will run off the same tank but I don't think the same hose hook-up will work, the connection is different I'm quite sure.

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Yes, the connection is different but you can get round that by using two hoses with the same connector to the tank on one end and the brand specific connector on the other.

ok so my brother and I got the motor running, fogged the cylinders replaced the spark plugs, and got it running after a little fooling around with it. Here are the only 2 things it does, if it's in neutral it will idle for only about 10 seconds. When we put it in drive and were able to open the throttle more we could get it to run for a good 30 seconds to a minute but then it dies. If we squeeze the pump ball on the tank line you can see some gas drips from the line in the motor. I am guessing it is a bad fuel line/fuel pump problem. Would you guys agree? Also I looked up the serial number and it is a 1967 model year.

I checked the fuel Filter and did a quick cleaning it didn't look clogged at all. Any recomendations on where to get a fuel pump and line kit for this motor? I have never really done much on a carb engine before but I am sure with a manual or video I could figure it out.

You can get all new fuel lines, connectors, and bulbs at Walmart. It seems to me that you have a fuel delivery problem, most likely too little fuel. Was the bubble firm when the motor was running?

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Yes the bubble is firm and if we squeeze it while running it will give to much gas and die

mavrick300 said:

Yes the bubble is firm and if we squeeze it while running it will give to much gas and die

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Sounds like it could be a carburetor problem. If you pump the primer bulb and it dies due to too much fuel your float may not be working just right. Clean the carburetor.

I do not know the specifics on this engine but it could be a ruptured or punctured diaphragm in the fuel pump also.

If you see any gas leaks it means the pump will lose vacuum and not draw the fuel from the tank - it is a common issue and an easy fix - replace the lines and tighten all fittings. The bulb should get hard and stay hard while the motor is off


clean your carbs as well - you can start by just removing the bowl and making sure there is no debris in there and wiping it out really good - check the seals and replace if brittle or cracked

basically, the fuel needs to get to the pump and then the carb with no air leaks from the first fitting on the tank forward

Not directly related to your listed problem, but also check the condition of the wiring as that age Merc ( and most anything else) might have bad insulation and need replacing. The 20 hp I inherited from my uncle looked like it just came off the showroom floor, but all the wiring was rotted (1971 model).