performance issue
 

Hi everyone i took the seacraft 20 sf out today the sea conditions were 2-3 chop. I could not get the engine to turn more than 4000 rpm. I took it out last week in more or less the same sea conditions and was cruising 4200 no problem with a WOT of 5200. I cant figure out why such a decrease in performance. The only thing I've done different from last time is i added 20 gallons of fuel with 4 OZ of marine STA-BIL and one more person. Could the fuel filter be clogged? Thanks in advance for any advice! Mercury 135 HP 1988.

Start by checking spark, compression, and linkage (make sure it's not binding on something) before ripping apart the fuel system. Sounds like your only running on 5 cylinders. Is the motor running rough at WOT? surging?

If you really suspect fuel system problems, the easiest way to check is run it on a 3 gal can of pre-mix fuel. If it runs fine then you know its up stream from your connection. If it still runs bad, then more digging, like BIG suggested.

I posted on THT - I think its down a cylinder about the right RPM

tautog did you get your SC a short time ago? Did it maybe sit for a long time?

Thanks guys for the quick responses the thing i forgot to mention was i moved the battery under the console and moved the shift and throttle cables a little bit. I also suspected it not running on all cylinders. Ill check spark today and linkage. I just purchased the boat recently it was my second time out. The previous owner had $1200 worth of work done just before i purchased that included new fuel lines carb cleaning, water pump, and thermostats. It also has new fuel tank done this year.

performance update
 

Hi guys the motor is getting spark on all six cylinders.
The compression test with all plugs removed and a cold motor were
#2 85
#4 85
#6 85

#1 85
#3 80
#5 85
I then took boat out in the bay and tested compression in one cylinder with all plugs still in the compression was between 95 and 100 on cylinder #2. I can't understand why I was getting 5200 rpm last weekend and then such a huge drop in rpm's. I'm sure the compression was the same last week. Could a failing fuel pump be the cause? Again Thanks everyone for you're help.

Did it sputter or have trouble starting or just fail to reach rpm?
You mentioned moving the throttle cables - could they been moved or adjusted enough restrict full range of their movement, say not open enough or be able to "floor it" on the gas? If your butterflies are restricting air flow you wont reach your rpms.

Hi Mcgilli thanks for responding to my thread. What I meant by moving the linkage cables was I slid some of the slack under the floor to make room for more storage. I opened the cowling when I was out on the wAter today and adjust the throttle a little bit I was able to get another 200 rpm's. The engine cranks up no problem no sputtering at all. Also when I moved the battery I swapped the engines power cables with the ones that were going the battery to the console when the battery was located in the stern. The cables from the motor were not long enough to reach console anyway both cables seem to be the same gauge. I just figured I threw that out there also. Does anyone know if there is any adjust on the shifter handle itself? It seems I have to push shifter handle pretty far forward before I get any response from motor. I'll probably pick up a service manual to find out how to adjust linkage. Thanks again!!

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

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.

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

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...;)

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.

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

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!

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?
http://lh4.googleusercontent.com/pub...zUc29JL_AOPzcg

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

http://www.wellcraftv20.com/gallery/...58/trigger.jpg

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

http://www.wellcraftv20.com/gallery/...8/P1010125.jpg

junk coil.

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

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.

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

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.

I just got home and unbolted airbox I pushed shifter handle all the way forward the butterflies on all carbs open about 1/4-1/2" only I then manually moved the linkage and they open all the way. McGillicuddy and Blue_heron you guys were right about the carbs butterflies. So I must of did something to the linkage when I slid the cables around under the console. Now I need to find a way to adjust this. I really appreciate everyones help it's nice to have guys who enjoy helping out a fellow seacraft owner. I will work on adjusting the cable and keep everyone posted after the next sea trial. Thanks again Tautog!

Hi Big i sent u a PM. Thanks.

That don't sound right. If something came loose, or the cable broke inside the sheath, maybe... But if that's the case, you should be able to verify it with a simple test.

The throttle cable inside the motor attaches to the throttle control lever. It is the lower of two levers with a common pivot point. The upper lever controls timing advance. If you can move the throttle control lever without moving the remote control, something is broke or something came loose at the other end. Try it both ways; see if you can move the throttle control lever on the motor without moving the remote control, then try holding the throttle control lever while your six year old moves the remote control. If there's any slop, the problem is probably in the cable or in the remote control. This should be done with the engine off. Especially the part with the six year old.

If there isn't any slop, it may be that the set screw on the throttle cam roller loosened up when you were running WOT in 2'-3' chop. There is a linkage from the throttle control arm to the throttle cam. The throttle cam has a tic mark on it. The cam roller on the bottom carb's linkage is supposed to engage the cam at the tic mark. If it doesn't engage at the tic mark, loosen the set screw a little more, adjust the roller so it hits the cam at the tic mark, and tighten the set screw.

Of course this is all wild speculation on my part since I haven't even seen the motor. You do need the factory service manual, or more pics and guidance from Tim (Bigshrimpin). He's the resident Merc guru. I just made a lucky guess, so I'm sticking my neck out.
Dave

WTG, Glad you found a logical explanation. Blue Heron is right on - Bigshrimpin is a motor-geek. Notice the logic he presented in his assessment. Catches a lot of fish, too:cool:

The fuel issue didn't seem right because you had mentioned all the fuel work done so recently.

The throttle cable could have been stretched (maybe in moving) and thus toast, or possibly a connection or screw came loose as Blue Heron noted. Nice to have a little helper around to move the throttle for you;). Good luck and let us know what you find. See you back at 5200 rpm in no time. PS manual on ebay out of NM for 19.95 or make offer ...

Hi McGillicuddy is the manual your'e referring to the one published by Clymer

Sorry about the last post i know now which one to look for Thanks.

something as simple as a bind in the cable can limit cable movement

Hi everyone had some free time today to investigate my controls. I found that the linkage was binding up on the plastic mounting block on the console. I was able to shave some of it down no more friction there. I also checked cables on the motor end, found that i have one inch of play on the bottom cable and half inch on the top cable. I was able to adjust it enough to get my carbs to open fully, but i cannot get them to open up full in reverse. I ran motor on muffs the idle is right where it should be and it shifts fine both directions. I will sea trial tomorrow to see if this works. I will keep posting my results. Thanks again guys!

Wowwwwwww. That's a ton, is the plastic cable end or adjusting collar or collar mount wallowed out? You need cables.

I didn't see any other worn areas. The linkage on the console end dug a groove into the plastic mounting block and the console too. All this tension must of stretched out the cable. The carbs were definitely being restricted. I do plan on getting new cables.

performance issue resolved
 

Hello again, i splashed the 20 sf for a sea trial today to test my throttle adjustment. The motor is able to get to WOT!! I was able to reach 5300 RPM engine trimmed up with two people and 1/4 tank of fuel in calm sea conditions. I ran the motor at WOT for about four minutes with no issues. I recorded the information on Navionics Mobile APP. Here are the printed results. Many thanks to all who responded. Blue_ Heron you were right about the carbs not being open all the way thanks again!!


Hello,
Check out the track made with Navionics USA!

Sea trial

Start Time: 10/27/11 11:28 AM
End Time: 10/27/11 11:35 AM

Active track info:

Distance: 2.0 mi
Total time: 0h 06'
Average Speed: 17.7 mph
Max Speed: 41.2 mph

Click on the attached .kmz file to see it in Google Earth!

Enjoy Navionics... Anytime, Anywhere..
The Navionics Mobile Team

Way to follow through 'Tog. 40+ is nice:cool:

Glad to see you've got your problem solved. Gilly deserves the credit for suggesting the carbs weren't opening up all the way. I just explained how to check it.
Dave