Stalling 89' OMC 4.3

[OMARiverRat]

Good morning everybody. I hope that one of you experts can shed some light on a problem I'm having. The subject is a 1989 Four Winns 190 Freedom w/ OMC Cobra 4.3 V6. After 2 1/2 years of sitting, the boat starts up, idles, and revs extremely smooth. However anything under load above 2800rpm +/- is out of the question. A quick spin around the lake yesterday proved this. The boat will plane, however at WOT the engine sputters and spits. A couple of times I could hear a backfire out of the carburetor. Any idea what could cause this?<br /><br />Here's what I know about the boat. It is not mine (not yet) and I want to make sure this is a simple fix before purchasing. It did sit 2 1/2 years w/ approx. 1/4 tank of gas. The owner topped it off w/ premium & added a can of heet to the tank. The carburetor was rebuilt by the owner (I wouldn't rule out a schotty rebuild job on the carb). Plug wires seem to be original, but I'm not sure about the plugs. The fuel/water separator has been recently replaced.<br /><br />Like I said she purrs like a kitten at idle. While cruising around the lake the temp gauge would not go above 100 degrees (Seems awful cold to me). <br /><br />Thanks for your help guys, and I look forward to hearing your replies.

 

[Don S]

Re: Stalling 89' OMC 4.3

Running at 100° probably means they pulled the thermostat out, maybe did that to mask an overheat problem. I would sure get one installed so it runs around 160 to 180.<br />Was the engine ever tuned up? New plugs, points, condeser, cap and rotor. Timing checked etc?<br />Below is a list of some of the possibilities of low WOT rpm.<br /><br />

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

Don -<br /><br />Thank you for the response. One thing I forgot to mention is that while on plane & cruising @ approx. 2500 rpm, moving the outdrive trim up or down caused almost what felt like a "surge" in the engine RPMs. Could this be some type of electrical problem? I'm not famiilar with OMCs. Does this year of OMC have an electronic ignition, or points & condensor?<br /><br />Thanks again

 

[Don S]

Re: Stalling 89' OMC 4.3

They had points ignition in 89.<br /><br />IF you had the drive all the way down, you were probably plowing the bow of the boat down. It needs to be trimmed up some to bring the bow up, which will also bring the rpm and speed up.

 

[Lou C]

Re: Stalling 89' OMC 4.3

Before you buy, make sure you can get OMC service where you are, many shops do not work on them. Mine had a similar problem, it actually was even worse, turned out to be a dirty carb and bad anti siphon valve. The valve is on the top of the gas tank. It prevents gas from siphoning into the bilge if there is a gas leak in the line from the tank to the fuel pump. <br />Re the stumble when trimming, there was a technical service bulletin about that, a good Johnson/Evinrude dealer may still have it. I'd check the batt cables and connections first, since the trim pump draws so much current it may be dropping it low enough to cause the ignition to cut out.<br />BTW, if this boat has carpet over wood floors, check them VERY carefully. Mine rotted out under the rear seat, needs a new floor, whole lotta work, but then it is 18 years old.<br />re the thermostat, I have had the same problem, when they get crudded up they won't close all the way and it runs too cold. I usually have to replace mine every 2 seasons or so. It should run right at 160 if everything is working well. Be aware that the one piece manifolds are very hard to find right now, a couple of places are making conversion kits. You are in a freswater area, so they may be OK still.

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

Thank you both for the good advice. I'm going to run out there tonight and do a compression check on each cylinder.<br /><br />I spoke w/ a local OMC technician and he didn't seem to think the "Surge" when trimming up and down was a problem. Apparently the OMC trim motors draw quite a bit of juice. I'm sure he was exxagerating when he said the motor is equivilant to that of a small block chevy starter. <br /><br />As for the thermostat - I've run into this problem before on my Crownline due to the silty Missouri River water. If only all mechanical problems were as easy to fix/replace as a thermostat. But then again, what fun would that be..........right??<br /><br />There appears to be a removable access cover at the aft side of the gas tank. I'll see if I can remove this and get a visual of the anti-siphon valve. At the same time I'll check the fuel tank vent tube. <br /><br />I've been browsing through some other threads in which boaters are having problems similar to mine, and another thing I'd like to check is the points in the distributor. This boat sat for 2 1/2 years so they may not be advancing properly. Could this possibly be the culprit? <br /><br />I'll post results of the compression check & anti-siphon valve tomorrow.<br /><br />Thanks again!

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

The compression test checked out good. 150,150,150,145,155,150. Knowing this, and considering the price on the boat I think I'm going to pick it up and call it a "project". I picked up the points & condensor ($17) yesterday which is where I think I'll start. I'll keep everyone posted w/ my progress. Thanks again to everyone for the help.

 

[THE BEEF]

Re: Stalling 89' OMC 4.3

RAT:<br />Im confused .When you talk about the trim motors are you talking about a mechanical<br />trim like my 800 stringer? I thought OMC Cobra<br />trimmed with hydraulic cylinders at the drive.<br />The 800 stringer does use a healthy motor.<br />On mine I have a jackscrew in the front center mount<br />which raises and lowers the engine and drive together for the trim.<br />THE BEEF

 

[Boatin Bob]

Re: Stalling 89' OMC 4.3

Even though the Cobra uses hydraulics there is still hefty motor on the pump, has a 50amp fuse! Like Lou says check ALL battery cable connections, both ends.

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

Beef - I'm talking about the hydraulic trim pump. I haven't looked into this yet but I will do so shortly. <br /><br />As for everything else: Pulled the fuel/water separator off again, dumped it in a clear pail and found it was about 70% full of water. At the same time I checked the points - they're brand new & adjusted correctly. Checked the timing, and its ok as well. Took it to the lake, and she's still stalling @ approx. 2500rpm. <br /><br />The carb is being rebuilt as we speak. I checked the clear hose that connects the the fuel pump in search of a leaking diaphram, but no such luck. I'll keep updating you on my progress.

 

[Don S]

Re: Stalling 89' OMC 4.3

With that much water in the filter, there may still be some in the fuel tank and now it back in your filter, Might want to give it another check.<br /><br />One other thing you might try. Put a dwell meter on the points and run the engine. Run it up to where it would normally stall out and see if the dwell changes.

 

[KaGee]

Re: Stalling 89' OMC 4.3

Did you check out the advance weights in the distributor?

 

[lilmandavis]

Re: Stalling 89' OMC 4.3

i found out that the trim motor on my cobra drew some amps when my alt died. cruisin at plane tryin to get home. trimmed it up a bit, and it was like someone yanked the coil wire right off almost threw me up to the dash. but the steering wheel was in the way. when i hit the trim it killed the motor for a sec. i didnt hit the trim switch again till we got juice, lol ribs still hurt

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

Don - I pumped a few gallons of gas directly from the fuel tank, and all I got was good, straight gasoline. I also double-checked the fuel/water separator and it appears to be fine now. <br /><br />KaGee - I have not checked this. Does anybody have any documentation showing how to check the weights? I'm not familar w/ this procedure.<br /><br />Davis - This was my first thought also - the alternator is going bad. However at idle & cruising speed she's putting out around 14.5v!<br /><br />I took her to the local boat ramp last night, backed her in and tried a load test. She made it up to 3,800 rpm before she wanted to launch over the front of the trailer and into the bed of my pick-up truck. Before I couldn't get her over 2500 rpm. I haven't taken her out on the water yet, but I plan on doing so either tonight or tomorrow. I'll post my results.<br /><br />Thank you all for the help!

 

[KaGee]

Re: Stalling 89' OMC 4.3

To inspect your advance weights, you have to remove the rotor and the points mounting plate. The weights need to be free of corrosion and pivot freely. On rare occasion do the springs go bad. Mostly it just gets all crudy in there and the weights cannot move. When that happens, your timing cannot advance, causing your symptoms. IMO, this inspection should be done every Fall or Spring.<br /><br />EDIT NOTE: Be careful running your boat on the ramp like that. I know someone who tied up a motor doing it. The ramp was steep enough that the front end of the motor starved for oil.

 

[I/O WALDO]

Re: Stalling 89' OMC 4.3

Sounds lean,bettcha the(correctly done)carb rebuild fixes it if the fuel supply is good.(I/e anti-siphon,pump,filter,pick-up)

 

[OMARiverRat]

Re: Stalling 89' OMC 4.3

Here's the latest.<br /><br />New Fuel pump, freshly rebuilt carburetor. Took it to a local lake yesterday, she ran like a dream for the first 5 minutes. Once she heated up she began to cough & sputter at about 3,000 rpms. When I'd back off the throttle she'd cruise smoothly. <br /><br />Since she's only doing this after she's hot, could this be an ignition coil? The coil appears to be the original.

 

[Gary H NC]

Re: Stalling 89' OMC 4.3

I know this may sound strange but my 4.3 did the same thing.ran good untill it warmed up then would lose power at anything over 2600 rpms..<br />ended up replacing head gaskets and intake gaskets.Has run great since...strange but true..

 

[halffast]

Re: Stalling 89' OMC 4.3

Gary,<br /><br />Not strange at all. I've had one vehicle with a vacuum leak at the intake manifold and another with a leak at the carb base. Both ran fine until warm. Both stumbled/lost power above 2000 rpm.<br /><br />I suspect that OMARiverRat has the same problem. In my cases, the leaks were there hot or cold but the symptoms only showed up when the engines were (very) hot.<br /><br />The easiest way to test for this ON A VEHICLE is to use an unlit propane torch to feed propane to suspect areas with the engine idling. Any leak will suck in propane and the added fuel should make the engine run faster. HOWEVER,<br /><br />THIS IS DANGEROUS on a boat. Propane is heavier than air and could settle in the bilge where any spark could be disastrous.<br /><br />Hopefully another poster can suggest a better (safer) testing method.<br /><br />Bob

 

[I/O WALDO]

Re: Stalling 89' OMC 4.3

Spray a little carb.cleaner on the suspected areas and U will get the same,safer diagnostic results! (Wood seem that an engine,under low-vacuum,high load conditions wood knott be affected by a minor vacuum leak,especially if it idles oh-tay!)