Turning off engine...gets engine knock.

[pcoliver]

Hi..just bought a used 2003 176 BR. Nice boat. First time out in it today the engine knocks after I turn off the key and lasts for about 5 secs and finally turns off. I remember this happening in cars some time ago and was related to wrong or bad gas. Just wondering if there are any other sources of this problem besides bad gas. If it is bad gas anyone have rec on fuel additive?

Thanks

 

[txdyna65]

I searched and found a few threads on this topic. This one seemed to explain it best though.


http://clubsearay.com/forum/showthread.php?t=11101&highlight=dieseling

 

[pcoliver]

I searched and found a few threads on this topic. This one seemed to explain it best though.


http://clubsearay.com/forum/showthread.php?t=11101&highlight=dieseling

Thanks for the link. I actually bought some sea foam today so I'll try that tomorrow. I emailed the old owner of the boat and he said he used 93 octane all the time. I put in 87 today so I might jump to 89 first and in combination with the sea foam see if it helps and go from there.

 

[First Born]

Check your other post that mentioned this, think you may be turning the key after just putting in Neutral, like when you go to pick up a skier. I will try and find you a link explaining it.


edit: Just noticed the link above referenced the same thing

 

[pcoliver]

Check your other post that mentioned this, think you may be turning the key after just putting in Neutral, like when you go to pick up a skier. I will try and find you a link explaining it.


edit: Just noticed the link above referenced the same thing

Well I put in 89 octane and used the 5 -10 sec rule and didn't have problems. Thanks for the help!

 

[Zeppi]

I've had this problem when pulling a tube. I normally shut the engine off when pulling up to the person in the water. I've been a bit un easy pulling up to someone with the engine 1/2 runnng (even if it is in nutral). I guess I'm also miffed that a boat that is 2months old and has 50hrs on it is running this poorly. BTW I always run the blower motor.

 

[comsnark]

I've had this problem when pulling a tube. I normally shut the engine off when pulling up to the person in the water. I've been a bit un easy pulling up to someone with the engine 1/2 runnng (even if it is in nutral). I guess I'm also miffed that a boat that is 2months old and has 50hrs on it is running this poorly. BTW I always run the blower motor.

I too turn off my engines when approaching someone in the water (unless there is a compelling SAFETY reason to keep them running).

My friends and I had chartered a BlowBoat in the Carribean a few years back. It took us a few days to realize that one of the engines simply was NEVER in neutral. Made mooring really painful. With outdrives. . .one needs to be doubly careful. When I put the swim ladder down, I have on occassion pulled up the drives to trailer position so that swimmers remain aware where the props are located. They can be a hazard even with the engines off (sharp edges!)

 

[First Born]

When we are pulling skiers / boarders /or tube, I always explain the pick up procedure. How I am going to come back to you on my side so that you will see me and I will see you. How when you are done and ready to get back in the boat do not proceed to the boat until I say you are clear. I never turn the boat off while the person is going for another run but of course do when they plan to get back in the boat. Again we are talking about 5 seconds of letting it run in neutral prior to allowing them to approach the swim platform. Honestly the other option is to have them wait the 5 seconds of the thing dieseling prior to me feeling safe about them approaching the boat.

Wesley

 

[PlayDate]

Wesley has the right approach. After a hard run, unspent fuel is still in the manifold and higher than normal combustion chamber temperatures cause the engine to continue combustion the unspent fuel until it is exhausted.

Giving it a few seconds to clear itself reduces the chances of "dieseling". The higher grade fuel has a more precise combustion point which also reduces the problem. It happens on both carb and efi engines.

-John

 

[Dirtguy]

It's not "unspent fuel." It's the vaporized fuel and the chamber is still hot enough to ignite the mixture.

Higher octane makes it harder to ignite but has slightly more btu's.

The idea of waiting to shut off the engine after a hard run and letting it cool is a very sound one. It won't diesel because the chamber cools enough to not self ignite.

If you look in the manual, it does state what octane to use.

Letting it idle also acts like a blower since it draws the air through the carb where the vapor comes from, and pumps it out.

dg

 

[pcoliver]

If you look in the manual, it does state what octane to use.

dg

My manual only says use at least 87 Octane. If I can use that due to gas prices I will. 89 seemed to work better but I was also diligent about keeping it in neutral for 5 secs. Just didn't want to have to go to 93 octane.

Thanks,
Patrick

 

[First Born]

87 should be fine. Try it and let us know!!! :thumbsup:

 

[Dirtguy]

87 should be fine. But there are circumstances that could cause a slight increase in compression. Carbon deposits are a possibility. Add a slight over advanced condition and there you have it.

dg