1987 Evinrude 175 surging

[rolander]

The engine surges at wide open throttle. It gains power then dies off, feels just like it's picking up a cylinder or getting a burst of fuel.

I have had this problem for some time already. It is not fuel. I have cleaned carbs twice, reed valves are fine, fuel bubble is good. I also tried without the fuel bubble. No change. Fuel filter is clear and also even tried a different fuel tank. No change.

I have tried a couple of different control boxes thinking maybe something in the wiring was bad. No change. I also have tried new plugs and swapping all the coil packs around with a known good one also no change.

What do you guys think? I have not tried plug wires yet. Anything else I could be missing?

Thanks

[highcountry]

Only at full throttle, no skips or tach movement at other speeds? If you have the motor off for a little time do you have to re-pump the bulb or is it soft, it could be drawing a little air at the motor connector.

[rolander]

Only at full throttle will it surge like that. Running half throttle of 3/4 there is no surging. If I am idling the motor it will run just fine, however every now and then it will chug and want to die. Sometimes it recovers and keeps running other times it sneezes and dies.

After sitting I do not have to pump the fuel bulb. I have never let it sit for more then a couple of hours while fishing before restarting.

[highcountry]

The sneezing sounds more like an idle jet adjustment. You may be right about plugs and wires, hope someone else jumps in with some ideas.

[highcountry]

found this on iboats forum?Boat is up and running again !! Ran it on a seperate gas tank, ran great, pulled pick up tube, was clean and all intact, checked fuel check valve and found valve wasnt opening all the way and caused the engine to starve for fuel at full throttle, replace check valve and all is good to go.
Thanks everyone for your advice.

[rolander]

Yea I did some searching on the form as well. In fact I posted about this problem on Iboats last year.

I did take it out over the weekend and it does seem to surge at 3/4 throttle too.

I already eliminated my check valve. I tossed it into the garbage. There is no restrictions on the fuel side anymore.

[highcountry]

I'll bet you have a coil that is breaking down.

[leachbn]

I have run into this problem in the past and found the fuel line was the wrong size. The bigger engines require a 1/2 in fuel line. That means the line, the pump and any/all connectors. Hope this helps.

BOB

[rolander]

Originally posted by leachbn View Post

I have run into this problem in the past and found the fuel line was the wrong size. The bigger engines require a 1/2 in fuel line. That means the line, the pump and any/all connectors. Hope this helps.

BOB

Thanks, but I don't think it's fuel. I have had this motor on two boats now and the same problem on each of them. Plus if it were running out of fuel because of smaller gas lines or bad fuel pump wouldn't it sputter and spit like things that run out of fuel? This is a surge, no sputtering no spitting nothing, just like it gains power then loses it.

To me that screams electrical??

But I think I will pull up the floor and replace all the lines and connectors anyways just to eliminate this being a problem.