[jorge]

I'm having the same issue with sputters when turning the engine off, I also noticed that my speedometer stopped working and then started to work again??? any ideas on the speedometer, on the Sputters I'm going to try higher oct. gas, I have half a tank now should I re-fill with higher oct. now or wait for the tank to be empty? or close to it?

[Jbetschart]

I tried higher octane and it didn't make a difference so I settled on 87. I never put in 85.
I all added a few bottle of different additives to help clean things out. Like sea foam, Lucas oil over time. I also changed the plugs a few years ago and whatever the combo this year it has helped.
Good luck

S if you are using an 85 octane go ahead and mix it with a higher but if you are already using an 87 in think you are probably ok.

[mikeyt]

jorge: this thread is a couple of years old but if you do a site search for 'speedometer' or 'speedo' you will find numerous threads on that problem. For starters though i will suggest that it is likely the pickup hole in the front of the outdrive that became blocked and then cleared itself that caused your problem with the speedometer.

[mike699]

CHECK YOUR TIMING FIRST!! I had the same problem with my 5.0LX and ended up spending a lot on parts I didn't need when I could have fixed the problem by retarding my timing back to the correct 8 degrees BTDC. Checking the timing will require a timing light. You can buy one for $40 or borrow one from a friend. I'm not positive on the correct idle timing setting for your boat but I'm guessing it's around 8 degrees BTDC (before top dead center). Let me know if you have any other questions.

Mike

[rayzorback]

I had a 1996 Shabah with a 4.3 merc Alpha 1 outdrive. I had the dieseling problem too until a boat mechanic had me go up to 91 Octane. Never had a problem after that.

[grommett]

Although timing is a likely cause, it can also be caused by "coked" pistons (caused by running too rich) but in my case it was early signs of leaky exhaust manifolds. A very small amount of water was getting into the exhaust which would be blown straight out when the engine was running, but as soon as the engine was turned off the water got into the pistons and caused run-on. I didnt realise this at the time and the eventual result was hydro-lock and a broken starter motor! New manifolds sorted the problem.

[sterlib1971]

I have a 3.0 Mercruiser on my '03 SX8. I experienced the same thing. I started running high octane and it made a difference.

[95Z212]

My Z212's V8 does this sometimes after a hard ride or pulling skiers. I fixed it buy either letting it idle down a few seconds, and tossing in a bit of Sunoco 112 race fuel that I run in my motocross bike. Plus one gallon makes the thing smell great for a solid month I also run nothing but 93 with no ethanol. Thinking about switching to just racefuel next year.