94 250 TXRS problems

[Capt. Mark]

I have several problems with this engine. 1st problem was oil pump would overflow oil tank on engine. replaced float switch didn't help, disconnected oil pump and pre mix. No big deal. Then started a hesitation problem when throttling up from idle. Then became hard to start after sitting a week or so. Getting harder to start as time goes on. Engine seems to be missing but all plugs are firing. Example of problem for a day on the water goes as follows. Start the boat on the driveway at home the day before, launch, idle a little ways go to throttle up and it takes off fine, slow down for any reason and throttle up again and it surges 2 or 3 times and then takes off fine. Run 20 miles offshore fish 30 minutes to an hour hard to start. Now for the work preformed. Cleaned carbs, replaced fuel pumps, replaced fuel water filter, replaced fuel lines from engine fuel pumpsall the way to the tank, new fuel tank( not because of problems )Replaced head gaskets, exhaust gasket, water jacket gaskets. Can this be an electrical problem and not fuel?


Thanks
Capt. Mark

[Capt. Mark]

Yes. All carbs were rebuilt. I was thinking I have an issue with the stator or CDI unit itself. It is driving me nuts.

[Capt. Mark]

What should i look at next? I think i've done everything i can do to the fuel system. What about the fuel regulator, could this be the problem?

[jb123]

sounds like one or more carbs still clogged

[99yam40]

Use a fuel pressure/ vacuum gauge to make sure there is not a fuel delivery problem when you are having the problem. Pump pressure, sucking air, restriction in lines, etc.
A timing light on the different plug wires will show if any spark is going away and if the CDI is moving the timing around when the problem shows up.
I always think it is better to test things first to find a problem and then fix what needs fixing

If all is good it maybe back to the carbs again. Have you looked at the plugs again to see what they have to tell you?
Do you think it is a lack of fuel or too much at certain times or in certain cylinders.
Hole in pump diagram will effect certain cylinders, float adjustments or trash in needle and seat will affect different cylinders also and may cause a too rich mix causing hard start.
Just a few thoughts from a fellow boater.

[Capt. Mark]

I will take all the advice I can get. I am greatful for all suggestions. Fuel pumps are 1 year old, not rebuils but new. Fuel tank was replaced because of age and holes in the side and replaced fuel lines from tank to filter.Also replaced fill line and vent with new tank. Installed a new Racor filter with clear bottom to inspect fuel for water and trash and haven't seen either.Carbs were rebuilt 2 weeks after pump replacment. Checked the screen on the pickup tube inside the tank was clean. I have never been able to solve the oil pump problem. Almost all problems started after starting to mix oil and gas. It acts like a plugs are fouled when first started up but smooths out after a minute or so. The mechanics over here don't care for this model engine. I know this problem can be fixed just need to do the right process of elimination. Thanks for all the help guys.

[99yam40]

like I said testing things will give you something to eliminate or look at further.
Just because you replaced or cleaned does not mean that is not still a problem.
A motor needs compression, good spark on all cylinders at the right time, and the proper fuel/air mix to run properly. Test everything you can and eliminate as you go.