www.iFourWinns.com

I am hoping someone can help me out in diagnosign a problem. The Four Winns I have is a beautiful boat, no bottm paint, and in great condition. For the past 2 seasons, I have had a problem with idle quality on the engine. The idle is lumpy. I have changed dist. cap, rotor, plugs, wires and checked the timing. Also had the injectors cleaned and re-calibrated last year. The boat runs good off idle, but shakes when idling. This problem has only surfaced last season. Also, there is a black film on parts of the outdrive, which looks like a rich exhaust, as well as the hull area around the drive. It has a Throttle Body injection setup.

I am wondering what the problem might be. I thought possibly the fuel pump (the one in the back of the engine) but not sure if that would signify a lean versus rich condition if not working properly. Again, it is definitely running rich. I am hoping it has nothing to do with the module.


Any thoughts are appreciated!

Bill

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1998 Horizon 240
5.7GSi

Engine mounts properly torqued? Is there a 'sweet spot' up or down from the RPM you're targeting for idle? What fuel are you using?

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2007 Horizon 200
4.3L GXi/ SX 225 HP

Jim-

Thanks for the input. Mounts are solid and properly torques. Never had them off. As soon as I come slightly off idle, smooths right out. Fuel is same as I have been using...93 Octane.

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1998 Horizon 240
5.7GSi

My guess would be a bad sensor, but I can't get you any closer than that. Do you have a shop manual that you can look up sensor troubleshooting?

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Mike
2005 Four Winns 230/240
VP 5.7GXi/DP
1998 F-150 XLT
Boat Pic

If the black flm is indicative of a rich mixture at idle, it can mean either too much fuel or not enough air at idle. I don't know about the TBI internals on the VP engine, but I do know that on many fuel injected car engines there is an auxillary air bypass circuit that works at idle. At idle, if the throttle plate(s) are closed, this bypass allows air to enter the inlet manifold, bypassing the closed throttle plate orifice. This allows the throttle plates to be fully closed at idle and gives a much more accurate airflow than having the plates cranked slightly open. Sometimes the bypass is adjustable by an external screw, but very often that screw adjustment is "factory set" and is under a plug to comply with emmision requirements/ stop people fiddling with it. It might be worth looking for a blanked off hole on the TBI On some earlier FI setups and some carbs this bypass circuit is absent, the primary throttle plate has a small hole in it to allow air to pass through at idle.

If you do find such a plugged hole in the TBI body with a screw underneath it and decide to try adjusting it, I'd recommend you make a very careful note of the starting positions before you adjust anything, so you can get back to where you were to begin with!

Regards,

Graham

THanks for the responses guys.

Mike: which sensor are you speaking of? I will have to check that out.

Gaham: I believe you are speaking of an adle anjustment screw called an IVAC valve. I have checked that out as well and determined it is in working order. Got the procedure from my shop manual.

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1998 Horizon 240
5.7GSi

Just for "shits and giggles", remove, clean and reseat the main engine harness. I had a Vista 248 that was acting strange and it turned out after much troubleshooting to be that harness connection. Removed, cleaned and reattached...ran like a new engine.

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Jvalich
http://www.badcock.com

'04 FW 288 Vista "Mental Floss"

I'm not up to speed in regards to the evolution of sensors on marine engines, so I don't know which ones you have or don't have on a '98. But on the newer MPI engines, they have O2 sensors and most of the other things just like cars have, and if they go bad they can easily cause the symptoms you're describing.

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Mike
2005 Four Winns 230/240
VP 5.7GXi/DP
1998 F-150 XLT
Boat Pic

Thanks guys....I will check out both. Never thought about the harness or knew there might be an O2 sensor. It's a 1998....I have got to check out the manual again.

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1998 Horizon 240
5.7GSi