2001 DT225 looses 200-300 RPM's at around 4500

[Solarman]

Honestly, I'm thinking more along the lines of a TPS (throttle positon sensor), or possibly a gear counting coil breaking down at full throttle.

If you have a Suzuki service manual, you can ohm test the gear counting coil, the TPS requires a special jumper/ patch cord to test.

I'm thinking the TPS may be breaking down at WOT?

Also, while testing the gear counting coil, you can test the high condenser charge coil (it is part of the magneto used mostly at higher rpms - you will have to look at wiring schematic for wire colors to test), just to see if it is in the normal range?

It is always a good idea to run a can of seafoam in each tank of fuel unless you're running marine grade fuel, and know it is clean.

If you don't have a suzuki service manual, you might need to get one for these tests.

Good luck, post back on what you find out.

[dan34685]

Thanks Solarman.

Went out today and ran a full can of seafoam through the fuel/water separator. Emptied the filter gas into a glass, then added seaform 50/50 to the gas. Ran the engine for 5 minutes, then let it set for 15-20 minutes. Did that 3 times. Thought it did the trick but then on my way back to the dock while tacking 5.2 rpms, suddenly dropped to 4.4 rpms. The change was instant like something bumped the throttle. After that, I could increase the throttle and get a few more RPM's but the engine definitely was sluggish. Got back to the marina and pulled the plugs and they all (12) looked great. The gas looked great, no water at all.

I have a new fuel filter (15410-87D01) and fuel injector filter (15410-92e02) being delivered on Friday, so thats my next move. Did not try squeezing the bulb this time out but did last week and didn't get any different results.

Seems odd to me that I would get an immediate change in the RPM's from a clogged fuel line (somewhere). If that were the problem, wouldn't I get performance issues across all RPM ranges?

Thanks so much.

[Solarman]

Are you always buying fuel at same location?
Have you tried squeezing fuel bulb when this occurs?
My best guess, the motor is 19 years old, I would look at plugs to see if any are burning unusually different. Then I would check/ clean/or replace any filters after the VST, to the HP pump, and any going to fuel rail.

This is a start, try and report back.

Good luck, post back on what you find out.

[dan34685]

Hi all.

I have a 2001 DT225 that sometimes drops about 200-300 rpm at around 4500 rpms. Sometimes if I shut it down, and restart, I can get the revs back >5.3k on WOT. Sometime not. Doesn't happen all the time. First noticed it about two months ago, then it went away, then noticed it again this past week. Seems to be worse when I have a full boat of passengers. I've checked the fuel (which was good) and replaced the fuel/water separator, with no change in performance. My research has indicated it could be just about anything. Here's the list of potential faults.

1. Bad gas (Gas is good)
2. Bad fuel / water filter (replaced)
3. Clogged inline filters (somewhere?)
4. Clogged low pressure fuel filter
5. Clogged fuel injectors (Cleaned with seafoam)
6. Bad low pressure fuel pump (I think I have two of these?)
7. Bad Fuel injector pump
8. Clogged Fuel injector filter
9. Bad stator
10. Bad CPI (last replaced in 2014)
11. Bad fuel regulator
12. Low batteries? (2 banks reading 12.8V)
13. Old sparkplugs? (replaced about 100 hours ago)
14. Other?

My local suzuki service rep suggested I try a 'hail mary' can of seafoam, which I will do next week. His next guess was a clogged fuel injector filter (8).

Engine has 800 hours on it and gets run just about every week.

I don't really have the ability to haul my boat into a service facility and don't want to wait a few months for them to look at it. I'm fairly handy and have the time to self diagnose but am looking for help to understand what to do first, second, etc...

Any ideas would be greatly appreciated. Thanks all.