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I just dealt with a similar issue, not sure if it’s the same case as yours but worth a look.
https://forums.iboats.com/threads/mercruiser-4-3l-stumbles-at-3000rpm.778484/
Thought it was a timing sensor assembly, turned out to be wires coming out of alternator shorting out on the manifold...
What’s funny is I should have recognized it as electrical in nature must sooner. Not only that, I found it by dumb luck and not any sort of real diagnostic method.
After researching this, seems like it’s a very common issue.
Well another update.
Boat ran fine for about 30 minutes after replacing that ignition sensor. Then it crapped out again, same exact symptoms. While idling back to the dock, I happened to notice the battery voltage gauge flickering almost in synchrony with the rpm gauge. Still thought it was a...
SOLVED
Just wanted to update all of you on the resolution to this issue.
This ended up being a bad Ignition Sensor Assembly (part no 87-892150k2).
Thanks for all the incite to the issue.
Another possibly I just thought about after hours of youtube.
Any thoughts on it being a bad ignition coil? I glanced at the ignition coil thats in there now. It does have a slight film of oil on it, could be from anything I suppose over the years but is it possible the ignition coil has gone bad?
No I didnt, its just me so Im not sure how to increase the throttle at the helm and also look at whats happening in the carb.
As for as the muffs question goes: I dont live on a lake and the boat doesnt live in the water. The issue started last night with the boat on the water. Tonight, I was...
I can order the pressure gauge for $22, or I see that an OEM fuel pump is like $150, or $25 for some Chinese knockoff. I wonder if I just get the Chinese one for the same price as the inline fuel gauge. It should run for at least long enough for me to confirm or rule out the pump issue. That way...
You were correct,at first it was only underway and only at 3000rpm. But now things have changed and it happens anytime except at idle, which it seems to run fine.
Also, I dont think I have a mechanical fuel pump if thats what you were referring to, its part number 861155A3.
I personally...
Tonight was with muffs on. I ran it out of the water(muffs), and thats when it stumbled to climb rpm's with any amount of throttle.
Last night was on the water. It seems strange to me that this would be a carb issue as it ran fine on the water for over 30 minutes. It was then all of a sudden...
I cleaned the filter/screen in the carb, there wasn’t much in their.
However, when I tried running it tonight it idled perfectly fine, but giving it any throttle it immediately bogged down and then stumbled its way up to rpm’s. So when throttle was increased, the rpm’s would eventually increase...
I just want to clarify something.
When I said i replaced the fuel filter, I was referring to the fuel filter/water separator (looks just like an oil filter). However, after some research I now see that there is a fuel filter/screen that is in the fuel line, where the fuel line connects to the...
Iv never actually cleaned the carb, never thought I had a reason to honestly. Iv seen sea foam videos of them just spraying seafoam into the carb while the engine is running, followed by shutting down the engine and letting it soak for 15 minutes, followed by starting the engine and running it...
The fuel was premium ethanol-free fuel, filled last year at winterization (October). Iv always filled the tank full before winter storage, never had an issue like this.
Fuel filter was changed during winterization (October).
Iv never actually cleaned the carb, never thought I had a reason to...
2004 Mercruiser 4.3L
Thunderbolt V
Alpha 1 Gen 2
Engine S/N: 0m670495
Crownline 180BR
I took the boat out of storage today. It ran perfectly fine for about 30 minutes at varying rpms along our ride. After the first stop, we took off again and I normally like to cruise at about 3000rpm/22mph...
Can you fill me in more on this part (timing and adjusting idle rpm).
Iv searched through the owners manual and it doesn’t get into timing/idle speed. And I can’t find anything in the adults only section other than how to find tdc, nothing on the actual adjustment.
I’m more concerned with the...
