Desperately need help from the 40 Merc guys

[BRzuki]

I've got a 2003 40 hp Mercury that is giving me fits. Its the 59 ci 3 cylinder 2 -stroke motor.
I've had the reed plate worked over, the reed stops are still in place, but have been bent out it looks like. All the gaskets are good on the front end. Timing is set for maximum advance (I've played with this and haven't gotten any noticeable difference in performance). Has good even compression on all three cylinders at 140 psi exactly. And here's the kicker...it runs great with the stock 40 hp carbs.

However, with the 60 hp carbs, the newer WME- 45 models, top speed and performance is right around 5/8th throttle. If i give it more throttle, I actually see a drop in rpms and speed not a gain like I would expect. I've ran two sets of these carbs with no change. I've went as far as to ship both sets of carbs to a friend who put them on his motor, which is exactly like mine, just 2 years newer, and they ran awesome.

I'm running #62 jets with 87 octane fuel with an oil mix of 50:1 and Chris Carson sport reeds.

I've been dealing with this issue for some time and don't know where to go from here. Very frustrated and need some help.

Thanks

[Bill Van Steenwyk]

At the risk of sounding over simplistic and possibly insulting you, unless your friends motor was just EXACTLY like yours (you mention potential reed/reed stop problems, max spark advance, etc. as the condition of your engine and also a different model year) and being tested on the same type, size and wgt of boat, with the same prop, at the same set up height and kickout, it is very hard to compare carbs run on one engine with another, or any other parts run on one engine to another, especially as you mention you had to ship them to him which would also indicate a different location for the test.

You have a lot of variables just in your short description of the problem.

You mention his motor is 2 years newer., although you think they are the same. Have you checked the mfgr specs to be absolutely sure the motors are in fact the same?

[XpressHJ]

Not trying to be an a**...

Rev limiter disconected? You didn't mention it...

[BRzuki]

Rev limiter has been disconnected

Bill,

My motor and the other motor that the carbs ran great on are the exact same motors. Both 59 cubic inch 3 cylinder 40 mercurys. Both are long shaft, electric start and are on the same size (1548) boats. The reed plates were also done by the same individual. Spark plugs are the same and timing has been adjusted the same. I'm running in Southeastern Missouri and my friend is in Lake Charles, LA. Elevation differences are minute.

The motor runs up to 6000 rpms with a 14p prop when the 40 carbs are on there...put the 60's on the motor and it will run up to around 5900, but when more throttle is applied, rpms and speed start going down.

[Bill Van Steenwyk]

"Normally" the first thing thought of when the throttle is opened from a partial opening and the motor slows down is fuel starvation, although there can be other causes such as a faulty electronic ignition if so equipped, problem with stator, etc. Are you sure you are getting plenty of fuel to and thru the carbs when installed on your engine? Have you tried pumping the bulb in the line from the tank to the carbs when it starts starving for fuel. If it picks up and goes while pumping the bulb, then you have pretty well solved the problem, at least as far as diagnosing the problem. Then you still have to fix the obstruction.

You might check for tank vent completely open, partial fuel line/hose/filter blockage or any other type obstruction/constriction, fuel pump if crankcase vacumn operated having check valve or diapahram problems, and also as I also live in Missouri also and we have usually only ethanol based fuel sold at gas stations and that is where you get your fuel, that can cause problems also by breaking loose any deposits that may have been in the fuel system if you have just started using it or the motor is used infrequently and ethanol laced gas sits in the fuel system for long periods of time between use.

There are lots of smart folks on this site and I am sure you will get lots of suggestions here, but another place to try is "scream and fly" which has a very good tech forum for problems like this.

Good Luck


Add: You might check and see if you have something blocking the inlet needle/seat assembly also. It only takes a very small piece of trash to cause a problem. I am not familiar with these carbs but a lot of carbs have a plug that can be removed in the close vicinity of the inlet needle and seat so as to remove it. Usually you can get it out with a small socket set and then "flush" the carb by pumping the bulb and letting the gas run right thru the carb into a container of some type, hopefully not around the campfire when doing this.

[BRzuki]

I'm not positive that it is not starving for fuel...I really never thought about that until now. I'm keeping fresh fuel (no older than a week from the pump) in at all times and always add a stabilizer. I will check my fuel delivery and make certain that is not the problem.

[fs5]

mate take the reed stops out and fit the washer style one that the 55/60hp motors run.
when you fitted the carbs did the carby gaskest fit nice not over hanging a bit?
do you have a pic of your reed setup?
140 psi is good mate ,my old girl only pumps about 112psi

i forgot to ask what jets are you running the 60 carbs?

[fs5]

i just seen reread your post .062 jets are to much mate.a stock 60 only runs .060 and most guys lean them down.
i'm running .056 in my mine ,with a nice light coffee colour plug .i've tried .060 .058 and .056 .the .060 jets felt like a slug up top.

[biggdave92]

BR, take it with a grain of salt, but I'm wish FS5 on this. I think you need to go with a smaller main jet. You ought to get a set of each size down to .056 and set what happens.

[BRzuki]

The next size down that I have are 58's so I'll give them a try. I also removed the in-line fuel filter between the carb and the pump. Just gotta wait until monday to get back to my boat and try all of this stuff.

[BRzuki]

Where can I get the other size jets at specifically the 56's?

[Fastjeff57]

I wouldn't leave that filter after the pump out or you'll really have carb problems!

Are you reading plug colors? That would tell you a lot.

Jeff

[BRzuki]

I'm running a water/fuel filter separator so I have no worries of getting trash in the carbs.

I ran the motor yesterday and tried pumping the bulb with no change in performance, the fuel filter removal didn't help so I ran it at WOT for a little bit, pulled the kill switch and checked my plugs. Top plug was almost completely black, middle, and bottom plug were tan, but darker than what I would prefer. Obviously the top cylinder is getting flooded. After making a call it was brought up that it might be my fuel pump since it is partly actuated by the top cylinder. I luckily found a fuel pump kit at a shop a mile away and rebuilt the pump. One diaphragm looked good while the other had rubber delaminating. I ran out of time to run it again except at the house on a hose. I'm hoping that was the problem and it is fixed now.

I also put .060 main jets in one set of carbs and .058 mains in another set. Will test tomorrow to see if my top end problem is fixed and if I need to lean out further.

Thanks for all of the help guys.

[Bill Van Steenwyk]

Since you have asked for help, I will make a few more comments.

Usually complete fuel filter removal would not be recommended, especially a filter that was your last line of protection between the fuel pump and carbs.

It is very easy to check blockages by blowing into the fuel line on the tank side of whatever filter you want to check if you have multiple ones in the system, by disconnecting the line to that filter and then blowing directly into the filter itself. If difficult to get your mouth on the end of the filter, put a piece of tubing on it for better access. The reason for doing it that way would be to eliminate the possibility of letting anything that has managed to get past any other filters you might have, and is just sitting in the lines, have a direct path to the carbs when the last line of defense is removed (the filter you just took out).

You mention a water separator/filter that will take care of preventing anything from getting to the carbs, after the filter removal you report. Unless that filter/separator is located between the carbs and the fuel pump, by removing the filter you describe, you now have a direct path for any crud or corruption to get into the inlet needle seat portion of the carbs.
The reason I mention this is most water separating filters I have seen mount on the transom of the boat just upstream of the tank. Even if you are using a small "spin on" type, mounted on the motor itself, by removing the filter between the pump and carbs you still have the path I mentioned previously. Remember that there are other types of trash that can find their way into a fuel system, not just what might be in the fuel tank or fuel that you put in the tank. Inner lining of the fuel line, parts of the pump diaphram, and other things can get to the carbs from several sources. It all does not have to come from the tank, or even from between the pump and carbs. It can just be sitting in the fuel line, waiting to be pushed into the carbs if not protected by a filter.

All that being said, the other tips you have gotten from other posters may very well have you on the right track, if you have two plugs completely black, ALTHOUGH they can be this way if you do not perform your plug check from WOT as pointed out and described in an earlier post. I have a 150EFI Merc V6, and my surface gap plugs are ALWAYS black, unless I perform a plug check the way described. They will be black and sooty every time if I just put the boat on the trailer normally, and then pull the plugs.

One thing you did not mention in your original post was the sound of the motor when you went from the part throttle operation to full throttle. In addition to slowing down (or just not going any faster) did the engine sound like it was "four cycling"? If you know what I mean by that term, there is not much mistaking where the problem lies. It would almost certainly be too rich as several posters describe. Four cycling can be most clearly described as when the motor is at WOT there is no doubt all cylinders are NOT firing EACH REVOLUTION of the crank. When "four cycling" it sounds as though the cylinders are only firing ever other time, hence the term "four cycling", as normally you would consider normal operation as "two cycling" and firing normally, 3 times every revolution, as that is the type motor it is. (3 cylinders, and two cycle)

Hope you solve the problem and be sure to let us know. Also if you are using ethanol laced fuel, be sure and use all the fuel filter protection available, as the ethanol in the fuel will "scrub" the fuel tank, acts as a solvent on some fuel line, (although most fuel line sold now is supposedly ethanol resistant) and then all that stuff gets carried into the engine.

Good luck

[BRzuki]

I did the WOT/kill switch plug check on the water and not on the trailer. The plugs were as described. Only the top plug was black. The middle and bottom plugs were tanned.

I'm not sure if it was four-cycling or not, but the motor makes a different noise, like its getting bogged down.

I'll put the inline fuel filter back on as this made no difference in performance from my testing.

Thanks again.

[fs5]

your top carb might have a crap in the needle and seat mate.my top cylinder is always leaner then the bottom 2.
i had some dramas a while back where ethinol blended fuel deteriorated my primer bulb ,as in it dissolved in the fuel and made it through the the screw on filter fitted to the motor and clogged up the needle and seat flooding the carbs.but it did it on all 3 though.
its easy enough to see,it looks like a dark cloud/sludge in the filter bowl as you prime it.i run a inline fuel filter aswell nowdays and i havn't had a drama since.maybe worth looking at.

any merc dealer can get you the .056 jets,there exspensive little buggers they cost me $15 each over here.

[Bill Van Steenwyk]

if your fuel system looks to be OK after the other checks and jet change.

You mention on another site that the top plug is black but the other two look to be OK.
You might check for steady fire on that cylinder, WHILE UNDER LOAD and WOT, with a timing light around the top plug wire. If you go to that trouble, check them all.
Faulty ignition to that one plug could cause a problem, especially if you have a separate coil for each plug. I had a coil wire slip almost out of a coil on my V-6 but could not tell it until I pulled on it because of the "boot" over the access for the wire into the coil. The wire had come almost all the way out and was at least an inch or more from the contact up in the coil but was not able to see it because of the boot.

[proprider01us]

I had the same thing happen to me at a race this past season on my 4cyl Merc. Didn't find the problem until someone grabbed the wire and pulled on it. Since then, I've run a nylon tie wrap around each end if the plug wire where it attaches to the coil boot and plug boot.


if your fuel system looks to be OK after the other checks and jet change.

You mention on another site that the top plug is black but the other two look to be OK.
You might check for steady fire on that cylinder, WHILE UNDER LOAD and WOT, with a timing light around the top plug wire. If you go to that trouble, check them all.
Faulty ignition to that one plug could cause a problem, especially if you have a separate coil for each plug. I had a coil wire slip almost out of a coil on my V-6 but could not tell it until I pulled on it because of the "boot" over the access for the wire into the coil. The wire had come almost all the way out and was at least an inch or more from the contact up in the coil but was not able to see it because of the boot.

[BRzuki]

Got a chance to run the motor this evening after putting a new fuel pump kit in. It ran like a scalded dog. 400 rpms and 3 mph gained. I ran the .060 jets and did a WOT electrical shut down plug check and I need to lean it out a little more, but .058 is as far as I'm going to go down. Don't want to lean it out too much for when I'm running it in temperatures 30 to 40 degrees cooler than I ran it today.

[Bill Van Steenwyk]

Congratulations on the improvement in the way the motor is running now versus when you first posted.

One question: In your latest post you mention you put the fuel pump kit in and also changed jets, going down to a 60 I think you said. Did you make BOTH these changes at the same time?? If so it is difficult to figure out just which one of the changes made the most difference and/or actually solved the problem.

Reason I am curious is picking up RPM and speed after a fuel pump kit would almost certainly mean too lean as I first suggested, while improvement with the smaller jets would tend to point towards too rich as the problem as one or two others that were trying to help suggested.

I am sure you are very happy that the motor seems to be fixed now or at least running much better, but it would also be nice to know which thing you did solved the problem.

One thing you always want to do, at least when testing to try to improve performance (maybe when not just trying to fix a problem) is only make one change at a time. That way you know whether you are hurting or helping whatever you are trying to fix.

Glad it is running better now and hopefully you learned something from the problem with the motor this time that will help you in the future. You will not only save some money, but there is much satisfaction in solving problems like this yourself.

ADD: Another possible solution to what may have improved the running of the motor is that there was some obstruction in the line PARTIALLY blocking fuel flow and it ran out unnoticed with fuel when you were removing/reinstalling fuel line during the process of trying to diagnose and fix the problem. Also possible that the problem was caused by a little of both things you changed. Sounds like based on others experience with this same motor you were maybe a little rich for optimum running from the start which is the way motors usually are from the factory, and then you had the fuel pump problem come along and compound the problem. Another reason to be sure and let us know if you made both the changes at once.

[BRzuki]

The diaphragm on the front side of the pump that is actuated by the top cylinder via vacuum hose was breaking down (delaminating) thus flooding the top cylinder at WOT. Fixed that issue and it ran great. The jetting is just to get it leaned out to where I feel comfortable with it.

[Bill Van Steenwyk]

So, if I understand you correctly, when you installed the fuel pump kit, the motor immediately came to life and ran like you were wanting it to when you posted the first time.

In other words it ran like you had hoped WITHOUT making the jet change, but after the pump kit. Then at that point you installed the smaller jets??

Not trying to pain about this, BUT, if the pump kit fixed the problem WITHOUT the jets, then it was probably too lean to start with, or at least the way the problem was described would point that way, and starving for fuel.

On the other hand, if the motor did not come to life until AFTER the leaner jets were installed, too rich. Unless a de-laminating diaphram can cause a too rich condition which was somewhat indicated by the condition of the plug in the top cylinder. I have no experience with these motors, other than a fuel pump that is not working correctly, usually does not pump a sufficient amount of fuel. Perhaps a Merc technician will chime in here with just exactly what happens with de-lamination of the diaphram, and how that affects these pumps.

The reason I am trying to figure out what you did that solved the problem, is in addition to helping you with your specific problem, this site, and the technical forum itself, is designed to also help others and at this point I am happy you do not have a problem anymore, but unsure exactly what solved it so we can all learn from your experience.

[mercguy]

So, if I understand you correctly, when you installed the fuel pump kit, the motor immediately came to life and ran like you were wanting it to when you posted the first time.

In other words it ran like you had hoped WITHOUT making the jet change, but after the pump kit. Then at that point you installed the smaller jets??

Not trying to pain about this, BUT, if the pump kit fixed the problem WITHOUT the jets, then it was probably too lean to start with, or at least the way the problem was described would point that way, and starving for fuel.

On the other hand, if the motor did not come to life until AFTER the leaner jets were installed, too rich. Unless a de-laminating diaphram can cause a too rich condition which was somewhat indicated by the condition of the plug in the top cylinder. I have no experience with these motors, other than a fuel pump that is not working correctly, usually does not pump a sufficient amount of fuel. Perhaps a Merc technician will chime in here with just exactly what happens with de-lamination of the diaphram, and how that affects these pumps.

The reason I am trying to figure out what you did that solved the problem, is in addition to helping you with your specific problem, this site, and the technical forum itself, is designed to also help others and at this point I am happy you do not have a problem anymore, but unsure exactly what solved it so we can all learn from your experience.

Bill, when any of these pulse operated fuel pumps have a diaphragm rupture/tear, etc, the excess fuel will flood the cylinder the pulse (not vacuum as stated) is drawn from..............Yamahas are very susceptive to this problem, Mercs too.............as you might know, Merc eliminated the rubber check valves in the fuel pumps and have been using a plastic disc, since the alcohol/ethanol fuels would make the rubber disc curl up...........any time I service a Merc and it still has the paint on the fuel pump diaphragms, etc....I install a new fuel pump kit............

[Bill Van Steenwyk]

Daren:

Thanks for giving us the benefit of your Merc tech experience. I was hoping you would see this thread and chime in.

Last year when I rebuilt the lift pump on my V-6 EFI I wondered why the check valves had changed in design, from what was in the pump to what was in the kit, and your explanation about the rubber material makes perfect sense now with the comment about ethanol.

Thanks for the clarification and I'm glad the OP solved his problem.

[mercguy]

Daren:

Thanks for giving us the benefit of your Merc tech experience. I was hoping you would see this thread and chime in.

Last year when I rebuilt the lift pump on my V-6 EFI I wondered why the check valves had changed in design, from what was in the pump to what was in the kit, and your explanation about the rubber material makes perfect sense now with the comment about ethanol.

Thanks for the clarification and I'm glad the OP solved his problem.

Bill, I do have to apologize for not calling you back last year on your issue. What did you find to be the problem/problems???

PS: I owe you one!

[Bill Van Steenwyk]

Daren:
See post #17 in this thread.

[MTECHMARINE]

This is tricky, twice I thought I had too lean on carbs but was really too rich. I agree with that theory, lean it down.:eek:

[lcp]

what ratio do u guy run with the mercury 40hp seapro....i heard 1.63 kind of hard looking for props......anyone run with 1.83?