Johnson/Suzi 225 4 stroke running problem

Tim M · 29 October 2007, 13:10

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 · 29 October 2007, 13:30

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 · 29 October 2007, 13:52

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 · 29 October 2007, 14:12

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 · 29 October 2007, 14:33

Quote:

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 · 29 October 2007, 16:47

Quote:

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 · 29 October 2007, 17:54

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

Erin · 29 October 2007, 18:57

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 · 29 October 2007, 21:08

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 · 30 October 2007, 00:48

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

OceanEco · 30 October 2007, 01:01

There are Two fuel filters under the cowling. The secondary filter is much smaller. How many hours do you have on the engine? Have you had any overheats?

Chris · 30 October 2007, 20:55

Tim,

deffo sounds fuel related, I am suprised that Fairweather could not fix the problem?

Chris

Quote:

Originally Posted by 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.....

Tim M · 01 November 2007, 14:19

Following the comments on here I concluded that it must be a fuel problem. On Tuesday I went down to the boat with the intention of checking every bit of the fuel system that I could, to hopefully reveal a problem. I worked from the tank, back, checking all the hoses, connections, breather etc etc. I eventually got to the engine, checked the internal filters (yes there are two - I discovered anther small one). I then got to this "thing" which (you can tell I'm not a mechanic) I think is the pump (see photo). Anyway, I noticed that whatever it is has a drain valve on the bottom, with a small hose coming off it, as well as a breather screw on the top. I assumed that this must be to drain the fuel off, so I gave it a go. It did indeed drain the fuel out, but what was most interesting was that when I drain it out there were some bits of debris in the fuel. I flushed fuel through it and then out several times, then blow back up the hose, followed by more flushing and more blowing.

We have used the boat a few times since, just running around the harbour, and so far it seems fine. I did take it for a short test run at speed, where again it was fine. I'm hoping and praying that this was the problem as it seems to be a nice quick fix should it happen again. The proof will be this weekend when we take the boat to Weymouth for the BUSA Nationals.

What I find odd though is that debris managed to find it's way in there. The trouble originally started around the same time that the main transom mounted filter/separator got damaged, so we bypassed it for a week or so until I got a new one. That would still have left the two internal filters, neither of which had anything significant in. Any thoughts?

peterb · 01 November 2007, 15:00

Pleased you got that sorted Tim. Having used your Rib - its a really good piece of kit. And the engine was awesome when I was on it back in the summer.

Nos4r2 · 01 November 2007, 18:16

What did the debris look like?

Tim M · 01 November 2007, 19:42

It was tiny little its of brown/dark coloured crap

Nos4r2 · 01 November 2007, 22:53

Quote:

Originally Posted by Tim M

It was tiny little its of brown/dark coloured crap

Odd. Was it rubbery at all?

blufin · 02 November 2007, 00:59

that's your vapour seperator. theres usually a filter gauze before the pump pickup inside the unit that might be worth checking/replacing if you found debris.