Author Topic: 1999 merc. 40 hp 4 stroke problems  (Read 1176 times)

npauls

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1999 merc. 40 hp 4 stroke problems
« on: May 22, 2011, 11:32:39 PM »
Hey guys/gals

I have been having problems with my boat motor lately and thought maybe I could get some advise on here in what to look at trying to fix first. I don't really have any extra coin due to a back injury and being on disability so I am trying to see if I can fix it myself first. I doubt I will be able to so I will probably end up taking it in to a marine shop but it may be something easy that I have overlooked.

Tonight was the 3rd trip of the season in the boat. The first trip was just to make sure everything was running good but I only launched it in a lake with a 10km speed limit so I didn't open it up at all. The 2nd trip of the season was on the walleye opener at chin lake with my old man and it started up 2nd try without any problems at all. We took a run down to the east end and hit the highest speed I have seen in this boat since owning it without any problems at all. When I decided to go check out another spot after being anchored for an hour or so I noticed that my motor would get up to about half the speed that I normally can get it to and would cut out and start chugging. It was still spitting water fine and the gas line was free and clear with no kinks or anything in it. So when I got home I decided to put fresh gas, a can of sea foam, and new plugs in it.

I launched it tonight at keho for the 3rd trip of the year with a buddy and had a bit harder time starting it tonight but it only took 4-5 times and it was running good. We took a rip out northwest of the launch and shut it down to do a bit of lindy rigging around a drop out while back trolling. After not having alot of luck there we decided to go check the inlet canal for a bit. Well the same thing happened tonight as the other night at chin. We would get to about half speed and it would start cutting out and chugging so I checked the gas line again and it was fine. I shut the motor down and let it sit for a minute and started it back up. We got on plane and up to full speed in no time but while running to the inlet canal it started chugging at full speed. After back trolling around the inlet for awhile we decided we would see how the boat did running to the other end of the lake at the outlet and it chugged going full speed all the way down the lake. I shut it down again and backtrolled around the outlet for awhile and then decided to fire up the main motor and troll some cranks for some snot rockets for awhile. So we are working our way around the dam area and the motor completely cuts out a few times and then when we get it running and keep it running we noticed that the water isn't spraying so good out of the back anymore. I decided to put it in neutral to see what would happen and it would spit a good stream for a bit and then not so good for a few seconds. Then hit the neutral button and revd the motor up a bit and it would spray perfect the whole time the revs were up. But as soon as we started trolling cranks again it would sputter and shut off or have barely any water spray out.

Sorry for the long story but I wanted people to know exactly what I have had happening and was wondering if anyone has any idea what this could be and if it may be an easy fix or if I will have to take it to a marine shop and pay some big coin to get it fixed up?

Thanks in advance for any help.

Nate
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Paul

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #1 on: May 23, 2011, 10:50:09 AM »
Was the gas fresh from the pump?

Could be a few things, fuel filter or maybe the fuel pump is gunked up. I would pull the fuel filter and fuel pump and have a look. Also check your fuel tank for silt or chunks that may be plugging the fuel intake.

It really sounds like a fuel system issue to me.

npauls

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #2 on: May 23, 2011, 02:00:07 PM »
I am not much of a mechanic so I will have to see if I can get someone to look it over for me. I just can't afford to put money into it right now but had alot of plans for this summer in the boat. Hopefully it is something cheap and pretty easy to fix.
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lad

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #3 on: May 23, 2011, 07:32:00 PM »
I agree with it being a fuel problem. Make sure the tank is vented properly so it does not end up not being able to lift the fuel out of the tank. I would also make sure all the lines between the tank and the engine are sealing at every connection and there is not any cracks, pinholes etc. If it starts sucking air instead of fuel your exact symptoms will show up. If it is not vented properly, same issue.

npauls

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #4 on: May 23, 2011, 07:54:32 PM »
The tank is an in floor tank and I have never had a problem before this season. I did put new gas in the boat when I changed the plugs and added a can of seafoam. How should I go about checking the gas lines for pin holes? I just don't get why it would be fine when I put it away for winter but then have some problems at the beginning of the season.

Thanks for the help so far and I will see if I can get it figured out. Hopefully it is something simple like that and not anything to expensive. I will be out of town fishing the Travers tourney this coming week and weekend so I probably won't be able to get to it until next week.


Nate
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mooseknuckle

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #5 on: May 25, 2011, 02:51:01 PM »
check out iboats boating forum. You can pretty much narrow down your issues to one thread and get an answer to your problem. I had the same issue only on a 2 stroke. some guys there narroweed it down to the stator (no spark) and guess what I replaced the stator went out the next day and got 40mph @ 5400 rpm and have never looked back. Untill the next piece broke of course. ahhhhh boats. much like a women some times.
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mooseknuckle

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Re: 1999 merc. 40 hp 4 stroke problems
« Reply #6 on: May 25, 2011, 03:06:30 PM »
Sorry here is a link to the place you want to go.

http://forums.iboats.com/forumdisplay.php?f=25
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