Help with a 1977 55hp evinrude boat engine stalling?

Question

I recently bought a boat with a 1977 55hp Evinrude engine on it. The boat had set for 7 years with gas in the tank. I’m new to 2 cycle engines but I understand combustion engines and imagine it couldn’t be to much more difficult then a car engine. So I changed the fuel tank, bought a new battery and got it started. I didn’t change the fuel line but I did change the primer bulb. It ran good for a while in the yard with the hose hooked up to it so I decided to put it on the lake. It ran solid for about 15 min. then it bogged down and died. The fuel filter looked good when I first pulled it off and after running it on the lake it looked a little gummed up, I guess there was still a little old fuel in the line. So I cleaned the fuel filter like the owner’s manual told me to and put it back on but the boat still doesn’t run right. Now it will only run with the choke on. If I try to take the choke off it immediately dies. It tries to start with the choke off but it will not run. The engine came with a warm up lever on it and with that turned on with the choke the engine runs well but like I said as soon as I turn the choke off it dies. Any suggestions? Could it be clogged jets in the carb even though it ran fine for 15 minutes or so? Or could it all be just the fuel line? I’ve made sure it doesn’t have any kinks in it but I’ve heard the can internally collapse. Andy help will be appreciated.

Answer 1

First, get rid of that old fuel -- your 2-stroke is more sensitive to fuel quality than a modern engine with ECM to compensate for stuff like that.

Those carbs are surprisingly simple devices, and need to be rebuilt after sitting that long.

Like the other guy said, if it runs with choke engaged that pretty much rules out everything except gummed up hi-speed jets.  If fuel wasn't getting to the carbs the choke wouldn't help.

Remove carbs, disassemble, soak overnight in carb cleaner, blow out all passages with compressed air (or aerosol carb cleaner), reassemble with new carb kits, reinstall, link & sync, adjust slow speed mixture screws.

You can get carb kits & service manual at http://www.iboats.com - highly recommend the factory service manual, have one for my '79 - saved me literally $thousands over the last 5 years.

Replace the water pump impeller -- after sitting so long the vanes will take on a "set", and be much less effective.  Or worse it's started to dry rot -- you don't want pieces of impeller blocking your water jacket.

Change the gear oil, any water in there you'll need to do the lower unit seals.

Run it on fresh 87 octane gasoline & tcw3 certified oil, and Champion QL77JC4 plugs gapped at .030

Answer 2

follow the lines from the tank all the way into the engine and even into the carb and check/clean them. If it runs with choke than that means that it will run with fuel being directly injected into the engine (bypassing the carbs) so you may need to clean or maybe even rebuild your carbs. The fact that it was running fine in your yard tells me that something was probably left over in the line and during the launching/running process it shook loose or got clogged in the line.