Vintage Mercury 9.8 HP needs help

[Blue Kayak]

I have an old (maybe 1966) Mercury 110, 9.8 HP, 2 stroke. It had not been run in 20 years, and this summer I got to thinking it might be a good motor for the Minnesota River.

I had it checked out by a Mercury dealer. They checked the compression, replaced the impeller, and lubed the lower unit. I asked them to clean the carb, but they said it was fine. They ran it for a couple of hours at low speed with no problems.

The first three times I took it out there were no problems, other than being a little hard to start. The last time I took it out, it died on me while going at about 3/4 speed. After that it has been very hard to start. When it does start it idles fine in neutral. However, when I shift to forward it goes a short distance and then kills.

I thought perhaps some line had wrapped around the prop, but the prop spins easily in neutral and I don't see any line hanging from the prop.

I hope some of you more experienced boaters have some ideas.

Thanks,

[eurolarva]

What have you been mixing the gas with 50 to 1? With a motor that old it probably should be 24 to 1 for the first couple of gallons. I would look at the fuel pump. After that many years the diaphram is probably all dried up. I would also test spark in each cylinder and then recheck the carb. If the diaphram in the fuel pump broke down chances are a lot of it is in the float bowl of the carburator.

[Valv]

I agree with eurolarva, I cannot believe a mechanic didn't do all he said, knowing it wasn't ran in 20 years. God only knows what could be going wrong.

Also check all the fuel lines, fuel connector, etc. after that many years they are probably "cooked" and will disintegrate very easily, plugging your carb.

[Blue Kayak]

Thanks Eurolarva and Valv. It looks like I have some work to do. Valv -- I've been enjoying that depth finder you sold me.

[hydro]

Check the fuel system for a restriction. Look closely at your tank and see if there's rust inside. It will plug everything up and you will see the problem when the engine demands fuel as in open throttle load situations.

The fact that the dealer had it running well and now the problem shows up indicates that something changed once you had it on the boat. Dirty fuel is a prime suspect.

[Blue Kayak]

Thanks for the tip Hydro. I did put a new line and bulb on the old tank. The dealer looked at the tank and said it was okay. But, it was kind of a quick look. I'll drain the gas and look more carefully.