Merc 3.7L A1 runs fine, dies when shifted to neutral, wont start

RetiredOperator

Recruit
Joined
May 9, 2021
Messages
2
First post, First Boat, First Headache with said boat and I cannot find a thread covering my issue so Im posting one. I have a Mid 90s Merc 3.7L, it cold starts great, Idles fine and ill be out on lake for 15-30min, when Throttle back to neutral (gently or abruptly), to engage reverse (or even to just idle), she dies. Then she wont start for 10-15min. Once it sits a bit she starts back up and runs awesome. Then it happens again. I will say while trying to start it, I noticed there was no fuel in carb and since I was by myself on the lake it was tough to check spark but I didnt see any. But that may be because I was doing 200 things at once I dunno. Ive tried to replicate the issue with the boat on Muffs but just like at Mechanics shop, she runs great. Everything ignition wise is new/top of line stuff, fuel pump, lines, (actual fuel) etc is all brand new. Mechanic installed the neutral-reverse interrupter switch to see if that would help. It did not.
Im at my wits end guys, I am no ASE certified mechanic, but Im not retarded either. This motor is so simple but its kicking my ass, any help would be appreciated! Thank you guys!🙄🤮🇺🇸
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,447
If the shift interrupt is activating it signals a new lower shift cable is needed
Start the motor and shift into fwd, neut, and reverse, switch activates,means corrosion or bad cable.
 

RetiredOperator

Recruit
Joined
May 9, 2021
Messages
2
Like I said it only does it once its been out on the lake running. Cant get it to do it at home on Muffs and neither can the mechanic. But soon as its under load for 20min it does it. Then after it sits, it starts back up no problem.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Check vent and vent line to the fuel tank?
Sounds like you're going to have to go out with a bunch of diagnostic gear and do a bit of old fashion troubleshooting.
I'd start by installing a fuel pump pressure gauge and fitting in the fuel line before you go and have it siting (securely) on the engine.
Also take a 'remote starter switch' and a timing light.

First thing to do is work if it's a fuel problem or ignition problem.

Chris....
 
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