Re: Boat Sputters after I turn it off
 

Btw: Almost forgot: A lean fuel mixture can also cause an engine to run overly-hot, and result in dieseling.

Jim

Re: Boat Sputters after I turn it off
 

I've also noticed engines do it if the idle is set high to compensate for a lean condition to prevent stalling when you shift into gear.
I use Marvels Mystery Oil to help with the low octane gas in our area, seems to help quite a bit. I only use Stabil in the winter, but it couldn't hurt.

Re: Boat Sputters after I turn it off
 

I second the use of the Marvel Mystery Oil -- worked well in my Toyota Avalon with 270K miles, too.

My store was out of it recently and the guy at the marina put K100 into my fill-up. Has anyone had experience with that product, good or bad?

Re: Boat Sputters after I turn it off
 

So I changed out all 8 plugs, switched to 87 octane and poured in so combustion cleaner and it ran great until the end of the afternoon and it happened again.

I am in Colorado so 5500 elevation.

I noticed it seems to happen after pulling the tubes at a slower pace for a while.

I will try adjusting the idle a bit!

Marvel Mystery Oil is that something that goes in the gas tank or a type of oil when I change it?
Can you find it at the auto parts or marine?

Thanks Guys.

Re: Boat Sputters after I turn it off
 

Marvels is a detergent that can be used in the gas to replace lead & improve octane and can be added to oil to free lifters & clean the crankcase. It's sold in auto parts stores and most department stores.

How fast is your boat idling and what is the engine temperature when it does this? if allowed to continue it can damage the engine.

Re: Boat Sputters after I turn it off
 

I usually use the simple solutions.

1. Try higher octane gas.
2. Let the engine idle for a minute to pump cool water though after running at speed.
3. Shut if off in gear.

Re: Boat Sputters after I turn it off
 

When we are running full open it runs about 150 for temp. I am not sure what it idles at Ill check next weekend.

What should it idle at?

It ran a little better yesterday but but I didn't pull anyone at slow speed for an extended time.

Re: Boat Sputters after I turn it off
 

Just a thought, check your timing.

Re: Boat Sputters after I turn it off
 

How do you check the timing?

Is this the plug gap?

Re: Boat Sputters after I turn it off
 

I changed the plugs like I mentioned and added some combustion cleaner and upped the octane but I am not through that entire tank yet.

Could it take a few tanks of the cleaner and the higher octane before I notice anything.