SUZUKI DT30C Low power problem, help?

[Evaldas0]

I recently started fixing up a SUZUKI DT30C that has been sitting for many years, not sure exactly but I think 5+. Had to get new ignition switches and stuff and it started up but wasn't running right, no surprise.
Cleaned the carburetors (really well) started to run a lot better at idle and much stronger in gear, had no hint of dying.
But now it seems to lack power and a lot of it. I know that the previous owner who I know well ran it with 4 people and he would get 20+ knots easily but now with just me on the boat I can barely climb to 16 knots.

So then,
- cleaned carbs again to make sure they weren't blocked
- cleaned fuel lines
- cleaned and checked the fuel pump
- checked spark plugs ( spark on all 3)
- checked coils with a multimeter ( all good)
- changed the pitch
- tried different timings ( with the timing switch on the engine)

not sure what else to check as I'm quite new to outboards but when it's in the water and sits in forward gear at low RPM and you push it to full throttle there is a burst of power and it feels perfect but then it instantly goes back to feeling sluggish.

Also had a tachometer that I hooked up and I think it measured kinda close to what RPM it actually was, maybe 100+- and at full throttle, it seems to only go about 4000 RPM in the water. Not sure if it helps.

Any suggestions would be greatly appreciated.

[Hernani]

Hi, what year ia your dt30c?, I find it interesting That Im having the exact same problem! mine ia a 1990 model 3 cyl. I mesured compression and got 115 psi on all 3 cylinders, then changed the coils (i have a complete spare engine) but it wasnt missfiring and nothing still slow. Next checked the timming with a gun and was around 26° btdc should rev easy with That advance. Next Im gonna test the TPS on the 2nd carb Im under the impression That by not reading well it might cause the CDI to retard Spark até around 4k rpm, but after reading the manual i have not found any defende to That. Still, ill give it a try and report back to you!

[Solarman]

Does the motor act like it is running out of fuel at full throttle, or does it feel like a cylinder is dropping out?

When you cleaned carbs, did you use compressed air to blow through ALL the passages and jets thoroughly?

If it acts like it's running out of fuel (surging a bit - acts like low on fuel), then it could be caused by float setting (slightly low); or, if float setting is too high then fuel overflows float bowl and goes into carb throat, this can cause motor to act like it's flooding out, and fuel may even leak out of carb throats in front.

Another possibility if fuel related, is if your fuel pump is not supplying enough fuel, either because the diaphragm is damaged, or the small check valves are damaged (usually not included in rebuild kit), or there is a restriction on the backside of the needle valve seat (trash)?

If your motor acts like it is timing related, then possibly the gear counting coil is not reading the teeth of the flywheel correctly (bad or mounting problem), or possibly the TPS (throttle positon switch) is bad?

If you have a Suzuki service manual you can test the gear counting coil and TPS per manual, or just replace if you think they are bad.

Good luck, post back on what you find out.