Rich @ idle = slow WOT?

[nola mike]

Took the boat out today, noticed it was smoking at idle, maybe running a bit rougher than usual. Opened it up and noticed it was slow, maybe 38 or so instead of 48. Rpms were 4300 with 2 aboard, usually 4500 with just me. In fact, speed was down over the entire rpm range. At idle, I noticed a bit of fuel leaking out of the venturis with the butterflies closed--I assume that's abnormal. So I took it back out at 4k rpms for 2 miles or so, and killed it and checked the plugs, which were black.
1. Does a few drops leaking at idle mean that I'm running rich across the board?
2. If I wasn't rich @ speed, should my plugs have cleaned up during my high speed run?
3. is a rich mixture enough to cause that dramatic loss of speed? It ran fine at higher rpms. I would have expected a loss of rpms as well.

What's the problem with the carb? Leaking needle valve/poor float adjustment? it's run fine all summer.

 

[dubs283]

Re: Rich @ idle = slow WOT?

could be time for a carb rebuild - the fouled plugs are indicative of a rich running condition

when you shut down, look down the carb and see if fuel is leaking down through the venturis - this is a sign of a carb problem

 

[Alpheus]

Re: Rich @ idle = slow WOT?

Check your fuel pressure. I know its sounds goofy but a fuel pump can increase its fuel pressure as it gets older.

If your fuel pressure checks out then its time for a carb rebuild. Your floats are getting heavy(fuel soaked) or your float needles are not sealing due to age...

 

[nola mike]

Re: Rich @ idle = slow WOT?

hmmm. ok, i'll check fuel pressure and compression next weekend. i got this (alledgedly) rebuilt carb on ebay to put in while i rebuilt mine. now i have some motivation to do it. real question is does a bit of leak at idle cause a loss of speed, but with the engine still able to rev properly? and is my engine only running rich at idle, or across the power band?

 

[JustJason]

Re: Rich @ idle = slow WOT?

You shouldn't see any fuel flowing at idle. All the fuel that does come's from the idle fuel discharge ports under the throttle blades. Time for a carb job.

 

[Alpheus]

Re: Rich @ idle = slow WOT?

What kind of carb is it???

 

[6meter]

Re: Rich @ idle = slow WOT?

Rich idle has nothing to do with WOT or anything above idle. Seperate circut inside carb.

 

[whitney]

Re: Rich @ idle = slow WOT?

Opened it up and noticed it was slow, maybe 38 or so instead of 48. Rpms were 4300 with 2 aboard, usually 4500 with just me. In fact, speed was down over the entire rpm range.

Something isn't adding up here. If what you say is true, you have soomething going on other than fuel problems. Same/similar RPM but 10 MPH slower means you have something wrong in the drive / prop.

Also to determine how the engine is running at higher rpm, do a "wot read". Run it at higher load long enough to possibly burn off any idle soot. Then throttle back and cut the motor right away. Let it cool off a bit and pull a plug.

 

[nola mike]

Re: Rich @ idle = slow WOT?

Also to determine how the engine is running at higher rpm, do a "wot read". Run it at higher load long enough to possibly burn off any idle soot. Then throttle back and cut the motor right away. Let it cool off a bit and pull a plug.

Yup, read my original post.
@alpheus: 2bbl mercarb
@6meter: problem is excess fuel through the main jets at idle (and maybe at speed).

again, i realize there's a prob at idle. just dont know if that translates to a rich mix at all speeds, and i dont know if that would be enough to kill my speed while allowing the rpms to climb normally.

 

[Aloysius]

Re: Rich @ idle = slow WOT?

Shouldn't slobber fuel at idle from the venturis. I don't see how a carburetor can be shipped sucesssfully without destroying the float level setting.

Time for a competent rebuild/readjustment.

 

[nola mike]

Re: Rich @ idle = slow WOT?

Ok, so it looks like the problems are unrelated. Cleaned the plugs and went on a 30 mile ride. Noticed that I wasn't porpoising when trimmed all the way up. Trimmed using the trailer switch and was doing 44 @ 4450 rpms with 2 aboard. Pulled plugs after that and they were clean. Still leaking fuel at idle though. So this week the plan is rebuild the carb and adjust the trim limit switch.

 

[Alpheus]

Re: Rich @ idle = slow WOT?

You still need to check fuel pressure. This forum is loaded with posts that deal with the same issue that you are having, they rebuild the carb with no fix. It very well could be the carb but a bad fuel pump will give you the very same problems on a rebuilt/new carb...

 

[Aloysius]

Re: Rich @ idle = slow WOT?

Good point alpheus.

 

[6meter]

Re: Rich @ idle = slow WOT?

Normal operating carbs have no fuel going through the main jets at idle, only through the idle circut controlled by the idle mixture screws. If its not this way you need as stated, a carb rebuild and check fuel pressure.

 

[krazykatz911]

Re: Rich @ idle = slow WOT?

Question, When I snap my throttle, and am looking down the carb, the second after the throttle is snapped, I see fuel squirt down on top of the throttle plates. Happens every time.

is this normal?