Help: 4 Stroke 15hp, been stored now wont idle down.

[Don Peacock]

Hi all, first post here.<br /><br />I took the boat out yesterday and everything worked fine except the 15hp Merc 4 stroke wouldn't idle below 1220rpm. Its been stored for 18months. My first thought is to pull the carb and use a couple cans of carb cleaner.<br /><br />If this was a 2 stroke, I'd already be up to my elbows in it, but since this is my first 4 stroke, I thought I'd ask here first. This engine was new in 2000 and probably has 200-300 hours with nothing but oil changes.<br /><br />BTW: The engine starts easily and runs smooth from 1220 rpm up to WOT. Gasoline is fresh.<br /><br />Thanks,<br />Don

 

[T_I_M]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

One of the first things to check is if the throttle plate on the carb is returning to fully closed , remove the cowl and check that all linkages are operating smoothly and not sticking.Another thing is some of those carbs had a accelerator pump at the base of the carb under the bowl, it maybe hung up in a partly open position.

 

[Don Peacock]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

Originally posted by T_I_M:<br /> One of the first things to check is if the throttle plate on the carb is returning to fully closed , remove the cowl and check that all linkages are operating smoothly and not sticking.Another thing is some of those carbs had a accelerator pump at the base of the carb under the bowl, it maybe hung up in a partly open position.

Thanks, I started it up in the front yard (with hose running water for cooling) and moved the linkages by hand. I think it wasn't closing all the way. By moving it by hand, I was able to get it to idle down to around 950 rpm. I think it used to idle down lower than that but I'll run it a few weekends and see if it loosens up before I do anything to it.<br /><br />Thanks again,<br />Don

 

[gss036]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

Add a can of Seafoam to your gas tank. Give the gas a little cleaning boost.

 

[T_I_M]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

4 strokes have a higher idle then 2 stokes, 950 +/- 50 rpm in neutral and 850 +/- 50 in gear.Get a goog quality spray lube a start working the linkage before you use it on your boat , nothing like a stuck throtle to ruin your day and boat.

 

[Don Peacock]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

Originally posted by gss036:<br /> Add a can of Seafoam to your gas tank. Give the gas a little cleaning boost.

Will the SeaFoam be OK for the I/O as well? As they use the same gas tank (80 Gal tank). The I/O is a Mercruiser 5.7L EFI.<br /><br />Thanks,<br />Don

 

[gss036]

Re: Help: 4 Stroke 15hp, been stored now wont idle down.

Yes, it will work just fine. I use SeaFoam to decarb older car engines. If you have a small gas can, you would not have to use so much SeaFoam to do the initial cleaning. Actually if you are running that big of a tank, go to Costco and get a box of the Chevron Techron fuel injector additive and use that. I use it all the time in my wife & daughter's vehicles, it seem to keep the check engine lights off by keeping the oxygen sensors clean and the other sensors clean. Ford seems to have several different sensors on thier engines.