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Where's Waldo?
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Discussion Starter #1
I'm going to run this up the flagpole here to see if there are ideas. My 2002 EFI Merc 4 stroke will not rev past about 3800 rpm while UNDER LOAD. It works fine in neutral. Max speed should be close to 40 mph and I'm lucky to get to 15 these days. Everyone and his brother has a different idea. Here's what I'm relatively sure it IS NOT...

The fuel - it is new and conditioned
The spark plugs - brand new and properly gapped
The Vapor Separator - it has been dismantled and cleaned.
The Fuel injectors - visually inspected Mercury cleaner used consistently.
The impeller - It pisses like a racehorse (a "Merc mechanic" said it might be overheating which was the dumbest answer I've heard yet.)

A friend said that his did that and it was one of he power pacs. That is possible but I cannot figure out how to test them and they would seem to affect starting and idling as well. It starts instantly and runs well at low speed and in neutral. They cost $140.00 each and are easily swapped out but I'd like to be more sure.

Another post I found online suggested the linkage but it seems to be doing what it's supposed to when observed "dry."

I am left without an answer and a slow boat. I suppose it could be the main computer board but that's a $1K piece that I don't want to replace on a whim.

Anyone else seen this? Any definitive solutions?

Sorry for the length of this. I would appreciate any thoughts out there.

Thanks,

MC
 

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With any engine you need fuel, fire and compression, what is spec on fuel pressure ? Check that, what is compression spec check that, coils you will need an ohm meter and you will need to know what they ohm at to check them, you can also ohm the injectors but that won't tell you if the are dirty and need cleaned, after checking all of that and all checks good, you may need to see a tech...
 

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Im guessing a coil and a compression check would be in order, Im no expert but it sound like some engine probs I have had in the past

Salmonid
 

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Premium Member
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Take it to a certified Mercury service shop, pay for an hours labor, and have them hook it up to the computer. They'll be able to tell you what's wrong in about ten seconds.
 

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Where's Waldo?
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Discussion Starter #6
Looks like that's what I'll have to do. The nearest one is 40 minutes away which is not that bad if they can actually solve it.

Thanks,

MC
 

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Does it hav a self check built into our dash? If no lights go fuel pressure. Plugged filter,bad pump or injector. Being it starts right is a good sign of ignition and fuel BUT low fuel will show @ open throttle being the pump cant keep up. You need a gauge from your auto store.
 
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If you have never replaced the fuel lines replace them. You might have a crack line and when it needs fuel it is sucking air thur a crack. This new gas are bad on old fuel lines. 2 cents. Ps seen this in my last motor 140 buck for fuel lines and labor sucked.
 

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AKA Dnavarroj
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1,364 Posts
I had the same problem on my 60 hp. I found the bad coil after testing it. Then came to find out mercury had a recall on it. My mecury dealer, didn't even tell me! Had to do the foot work myself. I replaced all the coil packs myself. Mecury gave me all new ones. Ran like a champ. No problem. Good luck.
 

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Where's Waldo?
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1,130 Posts
Discussion Starter #12
I had the same problem on my 60 hp. I found the bad coil after testing it. Then came to find out mercury had a recall on it. My mecury dealer, didn't even tell me! Had to do the foot work myself. I replaced all the coil packs myself. Mecury gave me all new ones. Ran like a champ. No problem. Good luck.

Now that one is interesting as the hours on the engine are still pretty low. How did you track that down? I have the serial number, of course, but I'm not finding anything searching the Mercury Marine site. I know they are easy to swap out, just didn't want to fork out $300.00 on a "possibility." I would have taken it to a shop by now but now my Jeep is in the shop with a tranny problem. Ugh, another hole in the ol' budget.

Thanks,

MC
 

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Bikes and fishing
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31 Posts
My 90 4strock was doing that it was the computor module. It was sending the wrong info to the motor. Merc paid for it. That was a couple of years ago.

Now my motor has a miss in it and I took it to Vic's today in Kent.
 

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AKA Dnavarroj
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1,364 Posts
i FOUND IT ON THE WEB THE RECALL. i GOOGLED IT AND BY ACCIDENT I FOUND THE RECALL. mercury gave me all new coils. good luck. it wasnt easy. delware marine took care of it for me.

Now that one is interesting as the hours on the engine are still pretty low. How did you track that down? I have the serial number, of course, but I'm not finding anything searching the Mercury Marine site. I know they are easy to swap out, just didn't want to fork out $300.00 on a "possibility." I would have taken it to a shop by now but now my Jeep is in the shop with a tranny problem. Ugh, another hole in the ol' budget.

Thanks,

MC
 

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Where's Waldo?
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1,130 Posts
Discussion Starter #15
So, I pretty much lucked out on this one. I was SURE it was in the electronics but turned out to be clogged injectors. I have taken care of them but bought it used after 9 years of mostly sitting around. I went to Stamper's in Miamisburg when I had the chance. They were able to clean the injectors instead of automatically replacing them. It was ready to go in two days for way less than I had feared. I took it out the day after I picked it up and it runs like a scalded dog. Better than ever in the three years I've had it.

Thanks for the suggestions from everyone. The best advice was to take it to a certified Merc guy who could cut through all the BS and just fix it.

MC
 
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