3.0 pops through carb while under slow speed

[bshattuck87]

Hey everyone, I've got a 3.0 Mercruiser in my '88 Bayliner 1950. While under slow speeds (around 7 mph) or so, after about 5 minutes of cruising like that it will randomly 'pop' through the carb or spark arrestor. It does it randomly and not every time. Also, when it does do it, it will 'pop' once and not continuously.

Brenton

 

[EMC 1810SS]

Re: 3.0 pops through carb while under slow speed

For it to pop thru the carb, that means that the the cylinder is firing and that intake valve is not fully closed (or sealing).

Probable Causes:

(A) ignition timing
(B) valve timing
(C) sticky intake valve
(D) burned intake valve
(E) broken intake valve spring
(F) faulty plug wires
(G) other.

 

[bshattuck87]

Re: 3.0 pops through carb while under slow speed

See what I'm thinking from that list would be option (F) faulty plug wires. This is why...

The PO put a new distribuitor cap on along with wires and plugs. The wire really weren't made for that motor. They were just some that worked in length. I can't remember which side at the moment, but either the plug side or distribuitor side one of them has a loose connection on all 4 wires because like I stated above, they weren't really made for the boat. One side of the wires fit like a glove, but the other side is slightly loose. I'll start with some correct wires first. Heck, while I'm at it I might as well put on a new cap, wires, and plugs just to ensure nothing else is incorrect. Thanks for that info.

Brenton

 

[90stingray]

Re: 3.0 pops through carb while under slow speed

What does your water seperator filter look like? Timing good? Engine harness connector clean and tight? Just some thoughts... in addition to the above suggestions.

 

[Bondo]

Re: 3.0 pops through carb while under slow speed

For it to pop thru the carb, that means that the the cylinder is firing and that intake valve is not fully closed (or sealing).

Probable Causes:

(A) ignition timing
(B) valve timing
(C) sticky intake valve
(D) burned intake valve
(E) broken intake valve spring
(F) faulty plug wires
(G) other.

Ayuh,... The 1st thing I'd be looking at is the fuel Filters, 'n Carb...

Popping through the carb is a symptom of a Lean condition...