Is this an overheat problem? (Dieseling problem solved)

[seilings]

Hi Guys,
I have been reading iBoats forum for quit a while and getting lot of useful information.
Thanks to all your contribution and I love this forum.

Now I am having some problem on my engine.
My boat is 2006 Maxum, I/O, and it has an MCM 4.3L 262cid Engine with Alpha One stern drive.
I has only 62 hours on the boat and Engine.
It runs great and had no problem at all, until two days ago I notice some thing weird:

If I have run the boat around for long time, let say 10 minutes in 3000 rpm, and when I shut off the engine, it won't stop immediately, I can hear it still running for 2 - 3 seconds, and like choking and then die. And I check the exhaust elbow, both sides were hot, can't keep my finger on for more than 2 seconds.
But if I let the engine idle for couple of minutes before I shut it off, then the engine stop right away.

The temperature always stays at 175 and never exceed that.
Engine starts great, runs smooth.

Is there any problem for this or is it a sign that something is going wrong now.

Thanks for all your thoughts!

 

[Bt Doctur]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

poor fuel, incorrect timing, hi engine temp will cause "dieseling". carbon buildup will too but with the low hours its doubtful.

 

[seilings]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

poor fuel, incorrect timing, hi engine temp will cause "dieseling". carbon buildup will too but with the low hours its doubtful.

Thank you Bt Doctur,

 

[Bondo]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Hi Guys,
I have been reading iBoats forum for quit a while and getting lot of useful information.
Thanks to all your contribution and I love this forum.

Now I am having some problem on my engine.
My boat is 2006 Maxum, I/O, and it has an MCM 4.3L 262cid Engine with Alpha One stern drive.
I has only 62 hours on the boat and Engine.
It runs great and had no problem at all, until two days ago I notice some thing weird:

If I have run the boat around for long time, let say 10 minutes in 3000 rpm, and when I shut off the engine, it won't stop immediately, I can hear it still running for 2 - 3 seconds, and like choking and then die. And I check the exhaust elbow, both sides were hot, can't keep my finger on for more than 2 seconds.
But if I let the engine idle for couple of minutes before I shut it off, then the engine stop right away.

The temperature always stays at 175 and never exceed that.
Engine starts great, runs smooth.

Is there any problem for this or is it a sign that something is going wrong now.

Thanks for all your thoughts!

Ayuh,.... Welcome Aboard,.... How long ago was yer motor/ drive Serviced,..??

Probably a Tune Up will fix it, or atleast point ya in the right direction,....

Desielin' is a Really Bad issue, that can easily Ruin yer motor,...

If yer not a wrench turner, get it into a Shop, Now,...

 

[seilings]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Ayuh,.... Welcome Aboard,.... How long ago was yer motor/ drive Serviced,..??

Probably a Tune Up will fix it, or atleast point ya in the right direction,....

Desielin' is a Really Bad issue, that can easily Ruin yer motor,...

If yer not a wrench turner, get it into a Shop, Now,...

I bought my boat last August, it is a 2006 Maxum, previous owner told me they had a mechanical guy came to their house to do winterize and service. So I think it didn't get service in couple of years.
I did winterize myself last winter, and at beginning of this season, the boat runs great. until recently it shows this weird dieseling. Hope to find out whether I can do the tune up or have to spend $ to dealer.
Thank you for your opinion.

 

[thumpar]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

You should normally let the engine idle for a minute or 2 before shutting it off.

 

[lirex3]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Sounds like it is a timing issue or possible bad gas, I only run 93 octane in my boat. Timing can make the motor run hotter.

 

[seilings]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

You should normally let the engine idle for a minute or 2 before shutting it off.

Yes, let it idle does help, thanks

 

[seilings]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Sounds like it is a timing issue or possible bad gas, I only run 93 octane in my boat. Timing can make the motor run hotter.

the Manuel says it use gas 87. All the gas station around my area have 87,89,91 with ethanol, only Chevron says their 94 doesn''t contain ethanol, maybe I should use that next time, but is it OK to use 94 ?

 

[thumpar]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Higher octane is not bad for an engine, only for the pocket book.

 

[seilings]

Re: Is this an overheat problem?

Re: Is this an overheat problem?

Just an update:

I replace the impeller, and looks it is still in a perfect shape, the rubber still soft. No pill off or any visible damage.

When the engine warms up and runs at idle, the riser is somewhat warm to touch (Not like before, even after high speed cruise, it would become cold very soon when down to idle speed).
Maybe the thermostat is the last thing I am going to check.
I notice the idle speed is around 1000 doesn't matter on muffs or in water, so I adjust the idle screw to make it run at 650 as manual spec. Also I bought a SeaForm engine treatment and will pouring into the gas tank, hope that would help too.
Will update later after put it into ocean this weekend.

 

[seilings]

Re: Is this an overheat problem? (Dieseling problem solved)

Final update:

Problem solved.

Gave almost 10 hours to my boat in water, and the dieseling problem never happens.
It is even better now after long run over 4000 rpm, and before I shut off the engine, I still let it idle for half minute, and the temperature drop from little over 175 to less than 175, and no more dieseling. I am so happy.

I also notice when using muffs on drive way, both sides of pee hole have steady stream of water (on idle speed around 700), before it was like splash water, so it is quite a difference and obvious the the new impeller is sucking up much more water.

Lesson learned, dieseling may indicates high engine temperature and it may indicates impeller problem.