Logo
FULL SITE MENU

1999 4.3 merc WOT misfire

A

aqualogic

New member
Need a little help troubleshooting. I have a 99 mercruiser 4.3 that I purchased 3 months ago. It seems to be misfiring when at wide open throttle. It make a very audible pop pop pop noise only at WOT. Sounds kind of like a rev limiter in a car. When I back off the throttle it clears right up. I have read other posts about this prob with mixed diagnosis. I know that the tach on the boat does not work so it is unplugged from behind the guage but still attached at the engine. If you plug the tach in the boat will not start at all. Could this be the culprit of my problem?? If I had to guess I would approx the RPM's to be around 3500-4000 when this popping occurs or any past 3/4 throttle. Thanks in advance for your help!
 
"[b]"Could this be the cul

""Could this be the culprit of my problem?? If I had to guess I would approx the RPM's to be around 3500-4000 when this popping occurs or any past 3/4 throttle."

Ayuh,... With the Tach, Unhooked, that Ain't the problem,...
I'd sooner think the fuel system is loaded up with Crap, causing a Lean condition at higher rpms..."
 
"If it's the rev limiter y

"If it's the rev limiter you are turning much more than 4000rpm. No way to be sure until you can get an accurate tach reading. Try to find a shop tach or photo tach to confirm. Don't recall exactly what the max rpm was on that year but probably around 4600 if carbed, 4800 or so if EFI. Limiter usually kicks in about 50-100 over the max rating."
 
"Bondo... Thanks for the advic

"Bondo... Thanks for the advice i bought a new filter and will be putting it on today. May be able to try going out tomorrow for a test run, weather permitting. Thanks again! Might you have any suggestions as to where I could find an oem or similiar tach for bayliners?"
 
"Any marine store or catalouge

"Any marine store or catalouge store or online store.

www.overtons.com is one source

Any I/O type tachometer will work, there usually is a dial on the back that will have settings for 4, 6 & 8 cylinders, just select 6."
 
The prices here at this site a

The prices here at this site are better then most.And they ship quick you could do worse and they stand behind everything they sell there.
 
"[b]"Bondo... Thanks for t

""Bondo... Thanks for the advice i bought a new filter and will be putting it on today. May be able to try going out tomorrow for a test run, weather permitting. Thanks again! <u>Might you have any suggestions as to where I could find an oem or similiar tach for bayliners?</u>"

Ayuh,... Right Here at <u>Marineengine</u> of course,..."
 
Ok.. Had a couple of very nice

Ok.. Had a couple of very nice days this week so I took the boat out for a test run. Seemed to be doing the same thing... I then thought that maybe I was in fact hitting the "limiter" so I changed the prop to a 14.5" X 21" which gave me a little more speed but still doing the pop pop pop noise at > 3/4 throttle. The top speed I can achieve before the noise with the 21" prop is 40. Any other suggestions as to what could remedy my problem? Thanks again guys!!
 
"[b]"I'd sooner think

""I'd sooner think the fuel system is loaded up with Crap, causing a Lean condition at higher rpms..."

Ayuh,... You still haven't told Us what the Induction system is,...
And,...
It Still sounds like it's goin' Lean, Starving for Fuel..."
 
Back
Top