Help... Don't know what's wrong with my 2002 merc 75hp

[kwhutto]

I have a 2002 merc 75hp on a fishing pontoon. Its docked at a marina. The last few times i have gone out, it has done the same thing. It idles well, then when i get outside the no wake i throttle up and it runs fine for a minute or two or 5 or so... Then it cuts back from 5k rpms to roughly 2k rpms. <br /><br />I had a mechanic come out twice and the first time he said he didnt see anything wrong with it, but checked all the plugs anyways. I came back out and tested it. Same thing. Then he came a second time and tuned it up and said it was fixed. I came out and tested it again and it did it again within 15 mins. Now he says it must be a statar which is more expensive he says...<br /><br />Once it cuts back like this, i can cut it off and recrank it and it will run well again for a while. Once it starts doing it, it is not just at full throttle either.. I can be going along at 2k rpms and it will just cut off.<br /><br />Does anyone have any idea what this is? I dont want to pay this guy a bunch of money if he is just throwing darts at the problem, which it seems like he is to me.<br /><br />Thanks.

 

[prolinews]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

check the fuel pump gas lines primer bulb etc sounds almost like it is stariving for fuel. I had one do that once had a pinched line .

 

[rabidfish]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

This is a staple of every good outboard(or inboard) mechanic. What I mean to say is it's a preliminary diagnostic step. <br /><br />Try hooking up a known good 6 gallon portable fuel tank. If the problem goes away, then you have a fuel delivery issue in the boat/tank/fuel lines, etc...<br /><br />If it doesn't, then the issue is with the engine.

 

[Silvertip]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

If you are using portable plastic tank(s), check them for plastic debris that wasn't cleaned out during the manufacturing process. I've seen where this has clogged the fuel pickup. Also check that the primer bulb is not being sucked flat when the engine begins to die as this is also a sign of a fuel pickup problem.

 

[P.V.]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

Yep, try a known good fuel tank and hose assy. Also, make sure that the vent is open on your orginal tank, or leave the cap loose!. If compression and spark is good, pull offending spark plug wires off when the motor is down on power, a real bi#*ch on a pontoon, huh?? If it's the fuel pump, squeezing the bulb will tell. Also, shooting fuel/carb cleaner into each venturi will tell you if it's running correctly or not!

 

[kwhutto]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

Another fact that I forgot to mention is that after i run it for a while like this, gas starts leaking somewhere down on the housing at a pretty rapid rate...

 

[Valv]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

I bet you have a broken/cracked fuel line inside motor or your carbs floats are stuck, and they let fuel overflow.<br />Starvation of fuel from bad line would be my guess.<br /><br />It's funny the mechanic didn't see any gas flowing on the side, I hope you didn't pay him much or nothing at all.

 

[DHPMARINE]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

kevin,glad you mentioned the rapid fuel leak.Did it happen when the mechanic was there?I think that is what is causing your problem.<br /><br />DHP

 

[2cycle]

Re: Help... Don't know what's wrong with my 2002 merc 75hp

If the fuel leak does not wind up to be the culprit, I would second what P.V. says re: the tank venting. My engine did the same thing and I pulled my hair out until I tried the portable tank test and found that my tank wasn't venting. <br /><br />Good luck!<br /><br />PS. I'm about 2.5 hrs north of you in SC - what lakes do you usually take the boat out on?