Troubleshooting a 6 HP outboard

[DaveC426913]

I just had my outboard serviced end of last season. When I got it a year ago, it would tend to start up on first pull.

Here's what I want to understand:

It will not run below medium-high speed. If I go one degree below medium, the motor will slow and eventually stall. At the same time, at medium-high speed, if I kick it into neutral, it immediately races.

So the upshot is there is a very narrow range of throttle, below which I cannot go lest it die, but it is too high to run routinely (jamming in and out of D and N like this will surely shorten its life).

I need to leave the engine be while I throw dock lines and such, and I need to be able to throw it into neutral without spending 30 seconds re-adjusting the throttle.

I tried fiddling with the fuel richness, didn't seem to do much.

It is putting me in a very dangerous situation. Some boat (mine or someone else's), or a dock or a crew is going to get injured.

 

[turbo]

Is it a 2-stoke? Most small outboards are, but I want to get this out of the way.

Where any modifications made during the service that might have changed the performance? Carbeurated small engines can be really sensitive to small changes, especially 2-strokes.

 

[DaveC426913]

Where any modifications made during the service that might have changed the performance? Carbeurated small engines can be really sensitive to small changes, especially 2-strokes.

2-stroke, yes.

It always had this problem. The servicing did not change it.

 

[Q_Goest]

So end of last year, you had it serviced and it worked great. Now you start it up at the beginning of the summer and you have problems.

Did you put gas http://www.thefarm.org/charities/i4at/surv/sta-bil.htm" in it when you put it away last year?

 

[stewartcs]

Yep...most likely that the fuel is bad. Happens most of the time when you don't drain the gas and lay it up for a while.

Drain the gas and then flush it. Put new gas in and you should be good to go. You can put STA-BIL or a similar product in with some new gas and try to cycle it through to flush it. Worked on my blower this year.

CS

 

[turbo]

I use Sta-bil in every single can of gas or diesel that I buy for home use/storage. That, and a proper appreciation for mix ratios can solve many (if not most) performance issues pretty well.

I'm thinking that Dave might have gone through this, and is confronting a change that is unrelated to fuel/lubricant issues. Still don't know, though.

 

[DaveC426913]

So end of last year, you had it serviced and it worked great. Now you start it up at the beginning of the summer and you have problems.

I do not seem to be making myself clear. I probably should not have complicated it by mentioing the servicing at all, but I knew that would have been the first suggestion.

It was like this when I got it, it is like this this year. The end-of-year service changed nothing.

I am not simply saying the motor works poorly, I'm saying that the throttle is on a hair-trigger. I think that's pretty common.


OK, having said all that, I'm going to give you the answers. You guys are the experts.

Did you put gas http://www.thefarm.org/charities/i4at/surv/sta-bil.htm" in it when you put it away last year?

No. I should have but I didn't.

I siphoned off the old gas and refilled it. (I confess I did not clean out the tank, it could very well have gunk in the bottom. Worse, any water will separate and sink.)



All this being said, with your advice, I may get the engine to start on the first pull and run better, true, but I doubt my throttle will be any less hair trigger, leaving me with the problem I'm posting about.

 

[DaveC426913]

That, and a proper appreciation for mix ratios can solve many (if not most) performance issues pretty well.

Really? So I shouldn't be loosey-goosey with the gas-oil ratio?

I'm thinking that Dave might have gone through this, and is confronting a change that is unrelated to fuel/lubricant issues. Still don't know, though.

I'm not really that knowledgeable about engines, just trying to diagnose cause and effect.

 

[Ranger Mike]

sounds to me like you got an intake vacuum leak. make sure the carb to intake gasket is ok..tighten carb bolts. check for loose bolts on the engine. one hot rod trick to check for intake leak is to squirt oil on the intake manifold..if idle speed changes, you found the leak. vac leaks make throttle very twitchy. if no leaks are found i think a carb rebuild is in order. over time the internal parts varnish up and air bleed passages get plugged up. these too will impact response as a plugged air bleed passage means venturi will not properly work to draw in fuel air mix..

 

[turbo]

Ranger Mike has a good idea there. The carb should mount to the engine sealed with a gasket that may have dried out or shrunk. Get the motor running and spray aerosol carb-cleaner around where that gasket is. If the motor steadies down, you have found the problem. Then you don't have to rebuild the carb - just remove it, clean the surfaces, install a new gasket and bolt it back on.

Edit: Forgot about configuration - if it's a twin, there might be a Y-shaped intake manifold, in which case there may be as many as 3 gaskets to spray looking for a leak.