www.iFourWinns.com

Hello all,

Finally got to see how fast my 225 Sundowner 351 OMC would run today after fixing the dropped plug wire - and the newly refurbished propeller that my repair shop tweaked for me...I am thrilled to say that we are running at approx 46 mph and 4700 rpm (it was fast enough to scare my wife and she made me slow down....)

However, towards the end of last weekend, we started having intermittent power issues, like surging as we finished up the day. When it died, it was rough to start, but then idled fined. Had it back out again today to replace the carpeting on my bunks and see if the dropped plug wire was the issue - and it was fantastic...

EXCEPT, the engine would, as you ease up to WOT (3000 - 4000) start surging, and initially, it was only at high end rpms but now it is doing it lower, like in the 2500 range as well, and when I discuss surging, I mean it will come up to speed and plane, and then just cut out almost a 1/3 of the rpms and kind of surge back and forth, almost to the point of sputtering out, unless I bring it back down to idle. Before I go take this to a mechanic and spend big bucks, I would like an opinion on what the issue here is. I am thinking fuel filter or fuel pump is failing, not getting gas to the carb. Otherwise the carb could be fouled/gunked up, or even in need of rebuild/replace. Is the lack of air displacement in the tiny engine compartment the cause? It ran exceptionally well with the engine deck seat off.....Any advice??? I am pulling my hair out, I just want to be able to boat this summer without being bit by the gremlins...

Guess I am on my own on this one? Pretty frustrated, cant really enjoy the boat at 90 degrees and max 3 mph....any advice other than starting with the plugs, wires, distributor, coil?

Also, I noticed today I have what looks to be an ecm unit on the port side running to the distributor as well not sure what that is since i am wholey unfamiliar with OMC/marine engine components.

Am I looking at am ignition issue, carb rebuild, or fuel pump/filter/separator/line replacement?

Look for the simple things first before you start picking a fight with the ECM..!!

Sure sounds like a fuel issue to me... change the fuel filter first (and get a spare while you are at it) - sounds like it's either picking up water or crap from your tank. If that doesn't do it, take the gas cap off just in case you are getting a blockage in the tank vent (anti siphon valve). If it ain't these, then you may have quite a bit of water in your tank that needs dumping or maybe the fuel pump is worth checking out or replacing.

Appears a number of people are seeing the same issues which is probably why no repsonse. I have responded to about 4 of these scenarios in the last 3 weeks...

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Alec

2006 Horizon 190
VP 4.3GL/SX, Sunsport

A big +1 on the fuel.

Try the filters first, then water, then pump.

If it's anything on the ignition side, it would most likely be popping, banging and or back firing.
In a very rare case, it could be the coil.

Since you have a 351 Ford, I am assuming it's an older unit with points. yes?

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1992 Baja 38 Special Twin 502 Mags

03 Stingray 3.0
88 261 Liberator 460 King Cobras
95 Bayliner 1850 3.0
77 Fiber Form 20ft 350/385hp
70 Wescraft 1800 SS 455 Jet

Lead, Follow, or get the Hell out of the Way!

looked at the filters, havent found anything yet, have a service tech looking at it now too, still surging after the carb rebuild and clean up, now the symptoms include difficulty starting after it dies. will eventually start up after a few tries, the mechanic now believes in the electrical...

I still have a hunch its the fuel pump or a clog in a line somewhere, outside of that, I would guess something in the ignitiion system causing it to lose spark, but gas is getting to the carb as it runs great on the muffs but surges under load...2nd week its been down now, hopefully we find something the following week...

Could water in the gas cause this? I would think water in the gas would cause this problem all the time, plus just did a full tank, with seafoam...is there a filter in the tank that could have clogged at the pickup?

Usually I would make sure the ignition system is OK before troubleshooting fuel...meaning that the plugs have to be not worn...gapped properly and not fouled...if a points ignition...the gap and dwell (really old school stuff from my early driveway mechanic days) have to be set right, base timing and timing advance must be OK...cap, rotor and wires should be checked too...

then for the fuel system...before even looking at the carb...the filters...vent for the gas tank...and the anti siphon valve (a spring loaded valve on the gas tank supply line to the fuel pump) can corrode and stick and cause fuel starvation (this happened to my boat)....it's 18 years old so there is a lot to check...

mine also ran fine on the muffs but could not plane out the boat....the anti siphon valve was the main culprit...carb needed rebuilding too...this was when it was about 15 years old....

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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

Well, all filters, pumps, valves have checked out functioning, new carburetor, okay on the pugs and wires, now we are down to ECM...that is likely the culprit.

If not the ECM, I have read about a faulty kill switch or shift module...something about a short or something. Anyway, any thoughts?>

my 5.8 surges a bit at low and idle RPM's....... nothing like you've described, once I rev up above 2500RPM I'm alright. I'm being told the issue with mine is a minor vaccume leak. going to do a lot of trouble shooting this weekend.... electrical, air flow, fuel system, ect....

this is my first inboard and I'm mechanically retarded to begin with but if I don't attemp I'll never learn.

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I treat my children well because I want the good diapers when I'm old....

4 kids, 2 dogs, 2 horses, 4 acres, an amazing wife, a boat and no time....

It's easier to beg for forgiveness than to ask for permission.

Okay here is where we are now...

New Holley Carb, new electronic fuel pump. No stalling any more or erratic surging. plugs, etc all check out, but have not tested coil, distributor, or ecu.

Boat was out today, ran great wot, planed out, and then after about 4 minutes, the mechanic/tech both witnessed it drop immediately from 4800 RPM to 2500 RPM and stay there, no matter the throttle demand. Mechanic describes this as "safe mode" where the engine will not go above 2500 rpms.

They are putting something on the distributor and a new coil pack on this week, but I am reading about oil pressure and temperature issues would lead to this, but they did not mention any overheating, and the gauge appears to read normal...

What would cause this safe mode persistence??? Summer has managed to slide right on by...and we have been out one solid day this year, what a BUMMER!!!

Just wanted to update everyone...turned out to be a combination of new carb, new electronic fuel pump, and new distributor. Runs like a champ now!!! Now on to update broken gauges, depth finder, speakers, etc etc etc...

had it out twice this weekend, it was a BLAST and easy enough on gas in calm waters too...

Good to hear you managed to find the problem. Always an issue with older motors - carby gaskets dry out, seals in pumps and I guess something in the distributor in your case...

Glad you have been enjoying it!

_________________


Alec

2006 Horizon 190
VP 4.3GL/SX, Sunsport