performance issue

[tautog_33]

Thanks Blue for the good advice! I do plan on buying the manual it must have something to do with the linkage because the motor was reach WOT rpm's just last week in a real tight 2-3 ft chop.

[gofastsandman]

Originally Posted by Blue_Heron

Do yourself a favor and buy the Mercury Factory Service Manual, not one of the after market manuals. I've had both and there's no comparison. You can probably find one on ebay. You'll need your engine's serial number in order to get the right manual.

The throttle cable adjustment is at the motor end of the cable. To check if it's a throttle adjustment problem, remove the cowl, and then remove the front air box cover. With the air box cover off, you'll be able to see the carb butterflies. With the engine off, push your throttle all the way forward. If the butterflies aren't wide open, that's your problem. It could be a simple matter of adjusting the throttle linkage, or the throttle cam could have slipped out of adjustment.

The manual will tell you how to fix either problem. Or you can check it out and post questions here.
Dave

Pull hard on the new cable away from the motah and center it in the "adjustment window".
This will allow for strech. You may have to come back and micro manage it.

Cheers,
GFS

[NoBones]

On a V6 it could be a coil dropping out, stator or trigger...
It's hard to tell when you are running if you are dropping a cyclinder.
Also your bottom carb may have trash in it as it is the first to get
junk in it..

Do a spark check first, then head for the fuel system.
Old fuel line will break down with the crap we have for gas now.
The liner in some fuel lines just breaks apart and clogs everything!!

Just my 2¢ worth...

[DonV]

I'm with Ken on this one....go straight to the carbs. There are very tiny jets and fuel pathways in the carb that can get clogged up very easily, especially the high speed jets and it's then a "no go" on high RPM.

[Bigshrimpin]

I suspect your compression gauge is off . . . A healthy 2.0L merc is generally 115 - 120psi. B/c all the cylinders are even and the motor starts easily and runs . . . sounds like a bad compression gauge.

A bad stator will cause the motor to run rough/misfire above 2500 - 3000 rpm (high speed coil). A bad switch boxes will cause one side of the motor not to fire.

A bad trigger can cause one or more cylinders not to fire, but they almost never fail (unless it's the sheathing on one of the wires).

Coils can fail . . . check grounds and make sure plug wires are snug.

If you have the idle stabilizer connected . . . you might consider removing it. Read why on screamandfly.com. Also . . . oil injection is problematic on these motors (2.0, 2.4 and 2.5L mercs). Merc makes a plug you can buy specifically for folks that want to remove the oil injection.

If you are concerned about high speed jets on the carbs being clogged . . . you can pull the cowling and the air box cover off the carbs and have someone else drive. Get on a plane (faster the better) and look down the throats of the carbs . . . you will see a nice fan spray of fuel. If one differs significantly from the other 5 . . . you likely have some crud blocking the high speed jet. If the spray is very different on one cylinder . . . back off and drive home at low speed and pull apart the carb with the issue (you may want to do all of them).

Is there a strong smell of fuel or any noticeable fuel leak? when you remove the cowling?

Did the motor get HOT? Are there any wires that look like they melted?

a bad fuel pump usually causes surging at higher speeds . . . if you pump the bulb while running it will usually overcome problems with low fuel pressure or a weak pump . . . then you know you need to rebuild it.


online merc manuals
http://1manual.com/Mercury%20manuals/intro.html

unfortunately they don't have anything back to 1988 . . . just 1992 and newer. There will be some relevant information in that manual.
http://1manual.com/Mercury%20manuals...52r3/cover.pdf

[tautog_33]

Thanks Big for the feedback. I had the cowling off yesterday after the engine was running for a while it wasn't hot I could keep my hand on the heads for at least five seconds or so. I also don't recall strong fuel smell. I did get the compression tester from autozone as as a rental. The carbs are starting to sound like the problem. I might also get an ohm meter to check the coils and stator, but I think they are fine since I'm getting spark to all cylinders. Unless it's not getting spark on one or two cylinders when I'm running unfortunately I don't think ther is a way to check for spark while underway. The motor has a pretty good holes of when I floor it from a dead stop. I wanted to try to give it more throttle with the cowling off yesterday, but I had my 6 year old with me couldnt trust him driving at those speeds. I will take your advice and look into the carbs next time out. I'll keep posting with the results. Thanks again!

[Bigshrimpin]

You can check the spark at idle with an inline spark tester . . . If it's good at a idle then your most likely good at high rpm. Does the motor bog at high RPM?


These are not likely your issue . . . but worth checking.



This is a bad trigger . . . see exposed wire.



junk coil.

**********************************

[tautog_33]

Thanks for the pics Big those will really help me out. The motor does not surge or bog down at high rpm. I can throw the shift handle down all the way from a stand still and get on plane in about 6 seconds with the motor trimmed up I am not running tabs yet. I want aware that a 1988 manual was unavailable. Is it worth it to buy one of the aftermarket manuals? Thanks big.

[Fr. Frank]

Get the Mercury manual. It is both more detailed, and more comprehensive.

[Bigshrimpin]

I'm not sure where you live in MA, but you are welcome to use (photocopy) mine of you want. They show up on ebay frequently.