Logo
FULL SITE MENU

Engine sputters and dies after crossing larger wake

M

mharvey

Member
I have a '96 Larson 194 SEI, 4.3 LX Merc, Thunderbolt Ign, 4 barrel carb, Alpha outdrive - Previous owner stated water in fuel caused some engine stops but my experience has been a sputter and stop after a larger wake. Then the throttle has to be pumped 8-10 times, or more, for a restart.
I have : drained/dried fuel tank
replaced fuel filter - found no water in merc. filter
checked elec. connection plug at back of engine
Spark wires, ignition wiring seems tight
Otherwise engine runs great, pulling skiers or cruising, all day long if no big jolt.

I was wondering if small amount of water was trapped in carb bowls and shaken into delivery with the jarring of the boat?? The sputter is immediately after wake crossing. When pumping throttle to restart, I am getting good streams of something, gas or water, into the carb. but it will not start until I pump what seems way too much fuel into the carb. and my imagination lets me think the liquid does not have a strong fuel odor. I have been reluctant to use a fuel drying additive, I do not want it in my tank, but I would put it in the filter bowl?

Any help is appreciated.
 
...experience has been a sputter and stop after a larger wake.
Click to expand...

I'm betting it is a momentary loss of ignition because of the "sputter". Make sure the shift interrupt switch is working properly and not loose causing it to shut off the ignition when crossing a wake. If that checks out you can perform a wire wriggle test while the engine idles. Shake the ignition 12 volt and ground wires up/down and side-to-side. Run your thumb and finger along the length of each wire and move it around while doing so. Start with the coil leads and move on to the TB ignition wires.

With the engine off remove, inspect and reconnect each wire connection in the ignition circuit. Pull off the distributor cap and inspect it carefully for any hairline cracks. Remove the rotor and check the optic trigger under it for any rust or corrosion. If you find any be suspicious.
 
Also pull the kill switch and reset it a few times.

The wires on the back of the key switch might need to be cleaned.

Remove the cables off the battery and clean the lugs, they might look clean but clean them anyway.

With the battery cables off follow the neg cable to the main ground remove and clean that one.

The main barrel plug, open it and inspect the insides, clean if green.

The starter cables need cleaning.

All done with the battery disconnected.

Now you should have all clean connections.

Run the boat.

If it happens again, at that moment with a spare spark plug pull a plug wire insert the spare plug hold it to the block and crank the motor, do you have spark ?

If yes then it's a fuel issue, post back and we will go from there.

Lets see first if it's a ignition issue or fuel issue.
 
Thanks for the input, both are leaning towards electrical. I might alter my "sputter" to include a hesitation and hard surge, then backfire? through the breather several times then die. Sorry it is not very technical, but also why would it not restart easily if it was electrical? I will begin the checks. Thanks.
 
...why would it not restart easily if it was electrical?
Click to expand...

Probably flooded from the sputter; as the engine dies it still inhales fuel.

...to include a hesitation and hard surge, then backfire?
Click to expand...

Backfire could be cross firing plugs caused by leaking plug wires, carbon tracking in the distributor, failing coil.
 
Temporarily hook up a auxilliary fuel tank(a 6 gallon outboard tank works well) to determine if the problem is fuel or ignition related.
 
Update, hydrolocked motor at lake this past weekend, pulled exhaust risers and the flappers were good but the riser to manifold gaskets were bad and allowing water into exhaust system and engine cylinders. This did not happen quickly, so I guess that has been my problem all along, as the exhaust pressure got lower than the water pressure, in goes the water. Now I cannot believe something is not bent in the motor, can anyone help with how to check or what to look for at startup after the repair and water removal from the cylinders?
 
Now I cannot believe something is not bent in the motor...
Click to expand...
That's not always the case. The water stops the engine. I assume you pulled the spark plugs and cranked the engine to blow out the water and changed the engine oil+filter. You'll need to do it a few times until the oil is no longer creamy if the engine injested alot of water when it locked. You didn't overheat the starter trying to crank the engine w/water in the cylinders did you?
 
No, the starter planetary broke while trying to crank the motor after it died while skiing. That was my clue to the hydrolock. I did drain the cylinders, fixed starter, replaced gaskets, and have not started it yet. The starter planetary has saved me before, so I am hoping for the best. I did notice one flapper stayed "closed" and the other side hung partially open, I thought that could be normal but both were pliable and moved OK. I did have water on both sides of the engine. Oil looks fine.
 
Ground out the coil HV lead w/key switch OFF. Pull the spark plugs out, put a strap wrench on the crank pulley and see if it will roll over.
 
I should have said this, but to get the water out I hand spun the prop while in gear, with the plugs out, and the engine turns over seemingly normal. Maybe I should not be using the prop? I think I am ready to start it and see what happens since I did not hear anything terrible when I spun it.
 
I would oil up the cylinders, put the plugs in, and crank it over with the helm kill switch off. That way the ignition is dead and it can't start.
If this checks out, then try starting it up.
Did you replace the risers and gaskets?

Rod
 
I replaced just the gaskets. Is there any reason to replace risers? Is anyone concerned about the shutter hanging open, I just do not want more water. I have had enough. The engine started up and ran good, smooth and quiet, now if I can just keep it that way.
 
A hung shutter should be replaced for sure.
Their purpose in life is to prevent backswells from running up the Y pipe and over the elbows when you stop suddenly.
As long as the gasket surfaces on the riser and manifolds are OK (smooth, no pitting) you should be good.
A definitive test would be to pressure test the water side of the manifolds as well, but they would have to come off the engine.

Rod
 
OK, this shutter operates freely, but it does not spring up closed on its own. It remains about 1/3 open. I think water coming up would push it closed, but the other side stayed closed on its own spring tension. These are the rubber shutters with a rod through the middle.
 
You just salvaged your engine from possible destruction. Is it worth it to you to have an "iffy" shutter fail and ruin the engine? Your call. I would replace them both. Cheap insurance to me.
 
That's the standard Merc type shutter, and if it was me, I would replace them both.
Here's the thing: When these deteriorate badly, they can fall apart and lose metal parts down into the exhaust Y and your outdrive. This can create problems if they get hung up in the water pump, drive shaft, or prop.
Your call, but don't say you weren't warned.

Rod
 
Ok, message heard. Thanks for all the input. I checked and these existing shutters were installed in 2003 but I will move toward another replacement since it is falling open.
 
Back
Top