Engine hiccups or misfires

[Braddock]

I have a 1994 Suzuki 75 horsepower outboard. Right now it seems to take a while to get gas flowing through it so it'll start, but when it gets up and going it seems to run better as it gets hotter obviously. My problem is is that I can't quite get it up to power as fast as it needs to be or should be. It seems to misfire or hiccup a bit and doesn't get up to speed as much as it should and has a bit of a stutter in it as well. When I get the boat up on plane it hiccups at full speed still. I've changed out the fuel line and I have changed out the connectors to the tank and the boat motor. I've cleaned out and got the carburetors working properly. I don't know what the problem could be besides a clog somewhere or air getting into a hose through a leak somewhere in the engine. Any other suggestions?

[Solarman]

Firstly, is this a 2 stroke dt model motor, or df, 4 stroke?
It is helpful to give us full info up front.
Does the motor idle after first starting up? Is it easier to start after it's first started, or harder if you let it sit awhile?
Have you adjusted all carb air mixture screws identically, by the manual?
When you cleaned/ rebuilt carbs did you blow all the tiny holes in carb and jets out, with compressed air, after soaking well?

So help us help you, by giving a little more info in your post. Good luck.

[Braddock]

The 2 stroke starts better as you run it, but if it sits it becomes harder to start again. We cleaned out the Jets really well.

[Solarman]

Braddock does the motor idle when started?
The jets have small holes, but so does the carb body. Those small holes provide air or fuel for proper running.
A missfire may be caused by spark jumping from plug wire to ground.
A stutter if electrical could be related to the throttle position sensor, the gear counting coil, the coils/ plug wires/ or even plugs. If fuel related, it could be fuel pump not supplying steady fuel, or carbs still not clean.
Hard to start after sitting a little while could be related to fuel pump not pulling/pumping fuel well, air leaking into fuel line while pump is pulling fuel, and/or fuel falling back to tank after motor is off.

You still have not given much history on this motor? Sometimes knowing how the motor was running, how long it was not running, if you found anything in carbs, trash, or whatever can help identify problems you might have.

Good luck. Post back how its going when able to let us know what you know, or if you find anything.

[Braddock]

When I finally get the 1994 Suzuki DT 2 stroke outboard engine to start after choking it 3 times with a full bulb and reving it up 3 times and get the gas flowing then it will idle well. The carbs were set the same after cleaning and it idles well. I replaced the fuel hose but I did not replace the fitting from the hose to the engine. When we cleaned out the carbs we did find a bit of white residue probably from using regular gas with the previous owner. It had been sitting for a year and a half when I got it. He informed me that it runs smooth but it gets a bit jerky like it is misfiring. I took the boat out once and it wouldn't even get up on a plane. I would push the throttle forward and the engine would drag so bad that it wouldn't even get enough power to get the nose down. I called him and he said that he always had to unscrew the screw on the bottom carburator to let the fuel drain out and then put fresh gas in it by squeezing the bulb in order for it to work again. All of this happened after I replaced the hose, emptied the fuel filter, replaced the impeller, replaced the spark plugs, and put fresh fuel in the gas tank. When I got back after close inspection I did notice the fuel line going from the fuel filter into the block had a serious kink in it and was being pinched between a clamp and the block. I straightened that out and I was able to get the boat back on a plane again, but it just seems like there is air or water in place of pure fuel moving into the engine, or a clog somewhere in the fuel lines. Or it seems like there is a problem with the spark plugs firing every time even though they are brand new.

I don't know what else I can tell you but I think there has to be air getting into the engine somewhere. My next move may be to put a new fitting on the end of the hose. There is no fuel leaking from it but maybe air is getting in during the boats operation.

Let me know if there is anything else I can tell you.

[Solarman]

Ok Braddock, this little bit of history could suggest a problem with the fuel pump.
Before buying a fuel pump kit, take the fuel pump apart, carefully. Inspect the clear-discs in the lower section closely, do they have any cracks/ are they fragmented/ intact? These clear-discs are check valves, that make the fuel diaphragms move in and out, causing the fuel to pump. If these discs are broken/ cracked/ missing, two things will happen. First problem, fuel pump will not pump enough fuel, and second problem, those pieces of clear discs will lodge on the backside of the float valve needle seat restricting fuel into the float bowl at higher rpms.
There is another problem if those clear-discs are damaged, they do not sell replacements in the rebuild kits, you have to buy a new pump to get those discs.

Good luck, post back when able, to let us know what you find out about the fuel pump.

We'll check other items once this is done.

[Hoosmatroos]

The white residue in the carb can indicate a corrosion issue. When water enters and sits in the carb for a while, the bowl and inner parts can corrode. It looks like a white powder when dry. If that's the issue then there is only one solution, replace the carbs. You can clean it but it will come back in a short time. I will look for some pictures tonight as an example.

/found one example on the web:

[Braddock]

It was nowhere near that bad but it was that. I'll take a look at the fuel pump when I get a chance. Thanks for helping me out. I'll respond when I find out more.

[Hoosmatroos]

If it was like that (In the picture is really bad) then you have one problem. If you clean this out it helps for that moment but after a few days or weeks, depending how bad the corrosion is, it will return. I was never able to make it go away. Replace is the only option.

If someone knows how to repair this kind of damage in a way that the white stuff doesn't come back I'll be interested too.

[Solarman]

Generally, I've found it only returns if moisture is still in the fuel. I have never had a re-occurence if only fuel, and or fuel and oil is running through carbs. But you do have to brush it clean thoroughly.

Good luck. Post back how its going when able.