I have a 37efi Briggs with 62 hours on it and was out running the other day and it started making almost like a spitting noise out of the exhaust around 4300-4400 rpm, I dropped down to 4000 rpm and it didn’t do it. I got it home and checked all fuel connections and they all seem fine, changed out the fuel filter and fuel water separator filter hoping it was fuel related, but it’s still doing it. I am not mechanically inclined at all so I didn’t check anything internally. I should note I hit two submerged stumps prior to this, I’m not sure if that could have caused it. I also checked the relays and put some rubber on top of them to create a snug fit in the cover because I heard they sometimes wiggle around in there, it seemed to have helped initially but then it went back to making the same sound. Picked up some new spark plugs today that I’ll throw in tomorrow but just wondering if anyone else has any idea what could be causing this. Any help would be greatly appreciated, thanks!

It could be a fuel related issue, tank vented?,try pumping the bulb if it helps, then i suspect the lift pump. Other possibilities, the harness is always suspect. Common harness fail points are at the relay box as u know, between the bottom of intake and the little metal sheild like to rub through the wires. The red power wire near starter likes to cook inside red rubber, lightly tug on wires to check that, if any stretch then u know the wire inside is smoked. Don’t overlook the obvious power and grounds . Other options are valves too tight and floating. A leakdown test would be nice. Spark plug boots arcing? Maybe intake gaskets got rocked by the stumps, check those. With the description its kinda tough to narrow down. Cam going flat another longshot.