www.iFourWinns.com

I have a 1993 Fourwinns 190 horizon with the ford 302 cobra efi/ OMC drive. Boat has been running GREAT. i start hearing a fluctuation in the idle jumping up and down. boat runs smooth at higher RPMS but at idle it surges up and down gradually surging higher and higher and eventually smoothing out for a moment and then surges again. i've tried the MAP sensor, IAC valve, TPS sensor, replacing the battery, cleaned the air filter, replaced the anti syphon valve not long ago, sprayed out the throttle body, fuel pump pressure is at 30 something psi. i haven't been able to find a vacum leak but i'm still looking. i'm so confused because it runs great at anything other than idle. any suggestions would be appreciated. thanks.

my next thought was possible the alternator? the electrical system isn't getting enough voltage? i looked at the gauge and its reading just above 12-13.

any input or suggestions would be appreciated

I really doubt that the voltage is the issue. (dash gauges are also not know for extreme accuracy) You might check for a vaccuum leak somewhere on the intake side. There are several methods for checking --- google intake air leak -- and you should find some. Most involve spraying different things around the intake and seeing if the engine reacts.

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DaleG -- West Palm Beach FL
2003 240Horizon -- 5.7Gi -Duoprop

If you are only getting a true 12-13 volts out of the alternator that is not good. The alternator should be outputting 14-15 volts.
An idle surge could be attributed to low voltage if the alternator is not charging and the battery begins to discharge. This has occurred several times on my racecar and both times it was because the alternator was not outputting the full 14+ volts.
I agree with the previous post as well. Check for vacuum leaks. You can do this by running the engine at 2000 rpms or so and using a can of carb cleaner give each hose and connection a squirt. If the rpms change when you squirt there is a leak.
Good luck and let us know what you find
Rob

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Anything Worth Doing Is Worth Overdoing
2001 Horizon 180

I posted this a couple of years ago and still working on the same problem with no solution. One mechanic blamed the ethanol in gas and suggested ValveTec additive. That didn't work either.
This will be the fourth season with this problem.

OMC 5.0L EFI Idle surge problem
I have an 1993 OMC 5.0L EFI 200 HP I/O that is garage kept when not in use. The boat has been trouble free until this perplexing problem.

The boat starts up and runs great and idles well and runs perfectly under load and operates at normal temps. (needle is in the middle of the guage. Never had overheating issue.)
When the motor is shut off after running at normal operating temps, everything is normal. I'll let it sit for at least 2 minutes and when I start it again while it's warm, the idle will surge until it eventually dies.
The computer is trying to compensate for the surging. Surge will go up to 1700 RPM, it does eventually die. If I start it up and put it into gear, it will run fine until I put it back into neutral. It will then go into the idle surge cycle.
If I let the motor cool for a few hours or overnight, the boat starts up idles perfectly again. If I shut it off and let it sit, and try again, the idle surge cycle continues. Gas is fresh and changed over a few times, tried STP gas treatment too.
I even drained the boat gas tank into the family car. Car ran fine.

I brought it into the shop and did a full tune up, and hooked it up to the computer with no error codes.
I changed out the IAC valve, temp sensor,water sensor and high pressure fuel pump, impellar. I even connected up a 5 gallon tank to isolate boat gas tank to eliminate that variable. Same surge.

All filters have been changed and even drained the gas tank to ensure it's water free. I thought about attacking the risers to see if they are clear and blockage free.

This just in: search Mustang EFI idle surge and a number of forums comes up. I'm working throgh them now.

Still sounds like a sensor (or a sensor connection) to me, but I stopped doing any real work on engines when they added computers to them, so I may be off in left field. You also might be onto something with the risers, especially if they're original.

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

All the sensors on my 5.0 L EFI motor were changed out. I now have my own stash of spare parts.
The mustang forums have blogging about this "surge demon" for years. Ford had a recall on the issue in 1994 and had a fix using the part in the link below. I've had this surge for five seasons now and 4 separate boat shops and countless of boat mechanics. I talked to a couple of Ford mechanics in the past two weeks and they recall this surge from that era motor. Stupid me, why didn't I search the Mustang blogs in the first place. Everypart on the OMC block has Ford Mustang DNA. I documented my problem on iboats.com and the feedback became a wild goose chase.

I'm now going through this checklist to see if I overlooked a sensor.
http://www.stangnet.com/mustang-forums/ ... klist.html

For $50 bucks it's worth a try as nothing else has worked. The part is on it's way.

http://k-mansparts.com/items/performanc ... detail.htm

Any chance of a bad connection at a sensor?

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

Do the basics FIRST..... pull your arrestor and see if the Throttle-bodys clean, I'll bet it's not. Have any belt squeaks from time to time?? The belt dust will get past the arrestor and dirty-up the T/B and the TPS sensor. My 93 5.0 had the "loping" idle too. The T/B was a mess so was the TPS. Cleaned it with Sensor-Safe cleaner while running on the muffs, lope gone..............

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Jimbo
Na. Ga.

2000 170 Horizon LS
4.3GL

Continued from my May 7th post. Here's the result. I have a solution for my Fourwinns.

The part was easy to install. While the IAC was off, I cleaned the noise supression filter that is fitted inside the adaptor. (I clean this filter every year with carb cleaner as air passes through it.) The motor makes an awfully loud sucking sound if that's not in place so the name of the part says it all.

I put everything back together and started it up. Idle when cold was 900 RPM and 700 when warm. I let it run in the driveway for a good 20 minutes so it was warmed up nicely. Shut it off for few minutes. Started it up and let it run 5 minutes. NO SURGE YAHOO!!!!!!.
I repeated the cycle a few times at various times. NO SURGE. OH THANK YOU K-Man and the Mustang Forums.

I started to play with the set screws on the plate and was able to hear the surge demon coming when I closed one of the set screws completely. I backed it off until the engine ran smooth. RPM was between 700-800.

When the Chicago winter finally breaks after Memorial Day, I'll get it in the water as the final test. At this very moment, I'm thrilled to have a solution. No more Idle Surge.


http://k-mansparts.com/items/performanc ... detail.htm[/quote]

That's great information, I bet that others would love to know the solution to the problem....
BTW if you have a dog clutch Cobra (93 should be) then the idle needs to be lower, like 550-600 in gear in the water. If you can get it as low as 600 on the water hose in neutral, it will probably be just right in the water. The lowest possible smooth idle on these drives really helps with getting them to shift smoothly.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Thanks for the info on the idle, it's great information. The long winter has erased my memory of where the idle falls. The motor always runs a bit differently on the water rather than earmuffs on the trailer.
Once I put some load on the motor, I 'll check the idle and try and get it in that 600 range using the set screws and just above the surge demon.