Johnson/Suzi 225 4 stroke running problem

[Tim M]

I have on the back of my rib a Johnson 225 4 stroke outboard (which is a rebadged suzi). It has run fine ever since we've had it, until recently. The problem started with it not running at high revs. Sometimes (normally after it had been running for a little while) it would stutter when you gave it more throttle, although pulling back on the throttle a bit would make it run ok again. This would normally happen at around 3000rpm. The problem has got worse, with it happening at lower revs. Now when you give it more throttle it just splutters a lot and goes down to idle speed and doesn't sound happy at all.

I have had SEA marine look at it, who thought it was the thermostat making the engine go into gaudian mode. A diagnostic check showed no errors at all - the engine "thinks" its ok. After the thermostat was tested it was concluded that that wasn't the problem. I then took the boat out of the water, and took it to Fairweather. Again, they hooked it up to a computer and it came back with no problems. It was still misbehaving though. Fairweather's only suggestion was that maybe the plugs needed chaning, so we did that, and still nothing. I have since replaced two fuel filters, and various other bits of "pluming" in the hope that that might cure it. It hasn't.

Has anyone got any suggestions. To recap the problem normally comes on after a little while of running. This seems to vary from a few minutes to maybe half an hour. The problem seems to be getting worse in that when the engine starts dying, it is revving less and less as the problem continues. As I said it's when you throttle forward, but it seems to improve when you throttle back - its almost like the engine is being flooded or something.

Any suggestions until the mechanic can have another look at it would be greatfully received!

[jwalker]

Tim, my first place of investigation would be the fuel filters but you say you've replaced them. Are you sure there isn't a wee one you've missed? It does sound like it could be fuel starvation. A blockage somewhere?.

[Tim M]

That's what I keep thinking but I don't see where it could be blocked. There is defiantly fuel getting to the engine, so that only leaves an "internal" blockage which I find hard to understand because we have two decent filters installed. It's so frustrating!

[codprawn]

Have you checked the tank breathers? Try taking the fuel cap off when the problem appears. Another possible cause is if you have a fuel computer the transducer may not be allowing enough fuel through. If you can connect up a totally seperate fuel tank straight top the engine for a bit.

Final thing I would do would be to replace the plugs - sometimes they break down under load.

[jwalker]

Originally Posted by Tim M

.. we have two decent filters installed.

Are these external filters? I don't know your engine so can't be specific but my Suzi had a fuel filter under the hood. It wasn't clear and looked a bit like a piece of larger diameter plastic pipe in the fuel line.

[jyasaki]

Originally Posted by jwalker

Are these external filters? I don't know your engine so can't be specific but my Suzi had a fuel filter under the hood. It wasn't clear and looked a bit like a piece of larger diameter plastic pipe in the fuel line.

There may also be another filter just prior to the fuel injection pump (if you have fuel injection.) It will probably be an in-line disposable type as well.


jky

[Millermob]

not anything to do with the primer bulb is it? blockages anywhere?

[Erin]

I had something very similar on my DF90. When it occured I could see the primer bulb being sucked in. It turned out there was some debris on the inlet fitting of the primary fuel filter (the one bolted to the transom). I had to take off the hose and fish out the lump of gunk, after which all was well.

Keith

[Tim M]

I have changed the plugs, but still no success.
I'm 99.9% sure we have checked all the filters - there is only one inside the engine which is a half size transom type filter/separator.
Codders, there is no fuel computer to worry about on this boat which rules that out.
Running off an external tank is the plan for tomorrow, as is replacing the priming bulb.....

[Nos4r2]

What's the fuel pump setup on that engine? Lift pump then injection pump or all-in-one?