Need your help! Engine bogging while accelerating
 

Hey guys I have a 1994 wellcraft scarab 22 with a 350 merc small block. I already posted about this before and appreciate that feedback. While planning out you can feel/hear the engine hesitate then Pick back up. I already replaced the fuel filter. Seemed better for sure but still some hesitation. The last couple times I have noticed when I really throttle down I can hear/feel telhe hesitation at higher speeds/rpm but if I am just cruising it runs perfectly. Really want to get this engine running properly as I just bought the boat recently. It was sitting for a little while before I bought it. All in all it runs fine but I would be much happier if it planned out easily and ran solid at high speed.

Appreciate your help.

-Tim

Have the carb rebuilt. Cheap and given the age of the boat it wouldn't hurt anyway. If you have all the old fuel out and a new filter then most likely it is an accelerator pump issue. A full tune-up should be on your to-do list as well if you cannot verify age of parts. Cap, rotor, wires, plugs.

Thank you for the quick response that's what I figured. From you experience how much is a full tune typically going to cost me?

Thanks,

Tim

i wouldn't worry about the tune-up at the moment. I always do my own wrenching so for me the cost is parts only and it is fairly inexpensive.

So for now my main priority should be to rebuild the carb? You think that's probably the issue?

Could be fuel.
Could be plugs and/or cap and rotor and/or wires
Could be carb's choke staying closed or varnish/e10 crud in carb

Can you do any work on your own ?

I have people who can help me for sure so yes I prefer to not pay the marina. What do you suggest I do to start? I will do as much as I can.

-Tim

If carbureted, Ck choke to see if fully opening. Should be within 2 minutes or so after engine is started.

Since you have to take off flame arrestor to do this, bring flame arrestor in and scrub out fins with water and dawn diswahing liquid. No one cleans these for some reason and they should.

Look at ignition wires. If Merc, the last two #'s are the year made. Q94 will be 1994. Q16 will be 2016 and etc,etc

Unscrew cap and take a look inside. Be careful, the hold down screws will fall out when cap turned over, so remove them before you do so.

Pull one or two spark plugs. Take a look to see if worn. As a heads up, most spark plug sockets won't clear the factory exhaust manifolds. You'll need a very thin wall deep socket vs a normal spark plug socket. Plugs are normally 5/8".

How long has boat sat ?

Excellent thanks for all of that its a huge help. My understanding is it was "sitting" the last couple seasons. The owner did run the boat here and there just not as much as years prior. It's in great shape but it definitely needs some engine love haha.

If you do not have thru hull exhaust (like many small blocks), then check to see if your flappers are intact in the top of the Y pipe. These flappers when they break loose will normally find their way into the drive, but sometimes will stay lodged in the Y pipe...where ever the flappers end up, they obstruct the exhaust flow and will cause a hesitation UNDER LOAD and shave off varying amounts of top speed. This is something that often gets overlooked on older boats and has confounded many a mechanic.

When you say changed the fuel filter do you meen the water separator on the bottom from the the motor. If so then there is also a fuel filter in the carb behind the inlet fuel line. This will cause a hesitation or stall out when at full throttle. If you only replaced the fuel separator I would replace the fuel filter in the carb first. It's cheap and may fix it so you can do all of the other tune up/ carb rebuilt at a more convient time.

Steel fuel lines and old gas = corrosion, which will get collected at the carb inlet filter. Done many of these last few years.

To the OP. Is the gas 2 yrs old ? If so, I would get rid of it or burn it at idle speeds only...doh.

I don't believe in the snake oil in the bottle but a bottle of Chevron Techron can do a bunch of good in a fuel system.

X2 well 3 actually.

You could have some sediment type contaminants in the fuel tank from old gas 'sitting' too long. My brother ran into this issue and when he would be getting on plane the sediment would sometimes restrict the pick-up screen at the rear of the fuel tank and restrict flow causing a bog. If he eased it on plane it would cruise just fine. Took a while to figure this one out! I recommend running on a small remote tank and see if it improves.

Appreciate the response, the boat DOES have thru hull exhaust. Does that change anything in regards to you response? Should I look for something different or specific?

If it has thru hull exhaust, then it will only have your issue with the exhaust in the silent mode.

That's correct I only replaced the water separator fuel filter...seems like carb worm is the patter here. Thanks for your help

All the fluids including the gas were replaced by my dad and I upon purchase for that very reason. Seems like some carb work is a must. The boats great and in excellent shape for a 95 just want it running tip top shape.

Appreciate that and definitely sounds similar. The funny thing is mine is better planning out when I give more throttle rather than less then just pull back. I think it's just needs a carb rebuild and maybe a little tune up.

Zip tie the choke wide open after you warm the motor up and go for a ride

Ok will do. What will this do? Should I be looking for anything specific during the ride?

If the spring is week or broken. You can pull it shut with vacuum as RPMs come up.