Merc up and dies...65hp 1971

Hi all,
Wondered if anyone has seen this before. 1971 Mercury 650 that had fits last year starting...that's how I acquired it very cheap from my father in law. I replaced the trigger, used, but it runs. Have been out a few times just fine. Went out last week with my daughter and the motor fell on it's face and quit after 14 miles. Finally figured out that fuel was the problem and if I pumped until I had a forearm the size of Popeye we could get back the 14 miles to home.

Picked up a diaphragm kit and installed. Back in the water today and 1/2 a mile at 3/4 throttle it died again. Not a slow death like running out of fuel, more like you shut the key off quick.

Pump ball but no start. Give it 5 minutes or so and it'd start and run. Back to shore so wife could pee and back out we went. Ran just above idle for better than an hour with not so much as a hiccup.

Seems if it was electrical, like a bad trigger, it would have acted up again due to heat. It's almost got to be fuel related now but why wouldn't it die slowly rather than just shutdown abruptly.

Has anyone seen this before? If I could lift the motor I swear I'd have sent it overboard by now. :lol:

Thank you for any help. If I can help any of you I'll certainly tell you everything I know about boat motors...shouldn't take much more than 3 or 4 minutes lol.

Bob

Sounds like ethanol is your problem. You should probably check your fuel lines and carburetor to see if ethanol has built up on the inside of them. Ethanol is really bad for an outboard. I cleaned and filtered my entire fuel system and got pieces of ethanol out the size of fingernails. I only use high octane gas with marine sta-bil every time without fail, no recent problems.

Ethanol free gas since the carbs were cleaned. I'm almost wondering if it got vapor locked. Checked the vent tonight when I got home and duhhhhh.....never was opened yesterday. Gonna give it a whirl tomorrow.

I thought it was rather odd, it ran so much better since the fuel pump rebuild for about 8 minutes or so. Closed vent would pretty much explain it. Between that and the first time out of the year forgetting the plug I feel like a real brain surgeon.

Well hopefully you don't make those mistakes again.