2000 Optimax 225 DFI reduces power at 3000 RPM

[stevechumo]

Hello everyone,
I'm a newbie to this forum, and I'm looking for some help on my 2000 Optimax 225 DFI. The motor runs fine and goes up to 4500 RPM for the first 5 minutes. Then it reduces the power to about 3000 RPM in which the speed is about 9 mph. If I give it more throttle, then it still doesn't go past 9 mph even the RPM goes high up.
I replaced the fuel lines, fuel filters, air compressor, and spark plugs. I took the air injectors and fuel injectors out to a shop to get them serviced. I never replaced the fuel pumps before. Where should I look?
Thanks.

The serial number is OT136125.
It's on a 23 ft Winner boat, walkaround type.
It happened either with only myself or multiple people.
It ran well many times before. My top speed was 30 mph at maybe 5000 RPM (I don't remember exact RPM). Usually, I only ran 25 mph that's probably around 4500 RPM.
The prop is 4 blades. It's always there since I bought the boat 2 years ago. I can't remember the prop size now.
I am not sure what elevation that you mean, but I go at the ocean on calm days.

[Savage]

9 (NINE)MPH??

[Bob]

9 mph... differential ?
Have you ever had the prop off ?
What style hub? I'm not sure if the old style rubber hub prop would go on an opti...just a thought that it might be a spun hub

[stevechumo]

Yes. The power is reduced at 9 mph. I could go over 4500 RPM at about 25 mph for the first 5 minutes. So that means there's nothing wrong with the prop. If the prop has issues, then it wouldn't let me go past 9 mph at the beginning. I checked the prop and it's normal. There maybe something that stops working right after it's hot or under heavy load after awhile. That's either overheating, or fuel starvation, or heated coil, or computer cut...etc. that I don't know.

[lpugh]

Lets start over:
Serial number of the motor
Specific boat and model
How heavy of a load
Has it done better before and if so what was the Top Speed and at what RPM
Specifically what prop is on it now
What is the elevation where you running the boat

[stevechumo]

The serial number is OT136125.
It's on a 23 ft Winner boat, walkaround type.
It happened either with only myself or multiple people.
It ran well many times before. My top speed was 30 mph at maybe 5000 RPM (I don't remember exact RPM). Usually, I only ran 25 mph that's probably around 4500 RPM.
The prop is 4 blades. It's always there since I bought the boat 2 years ago. I can't remember the prop size now.
I am not sure what elevation that you mean, but I go at the ocean on calm days.

[SilverFox579]

Let's also know if you're obtaining rpm from a Smartcraft device or analog tach.

4-blade doesn't tell us what we need to know, please post a picture if you don't know what specific prop, and brand, you have.

Elevation means altitude, if you were on the ocean when this occurred elevation is a given.

First thing I'd do is remove the prop and check the hub.

[EuropeanAM]

Agree that removal and inspection of the Prop Hub is going to be VERY wise.

If that is ok, start with the BASICS: Compression Test, Spark Test, Fuel Quality/Delivery/Air-Fuel Pressure Tests, and Maintenance History (as well as Current Needs) Review.

[stevechumo]

To check the hub, do I align & mark the hub and the prop, then run the boat in the water? If the marks aren't aligned after running, then is the hub bad?

[Bob]

If you have the older style hub that is the way to check it.
If you have the flo- torque style insert it should show damage and you can replace by yourself

[stevechumo]

I'll remove the prop on Sunday, take a picture on post it on here.
Thanks.

[stevechumo]

I took these pictures of the prop. Is there any issue with it?

[EuropeanAM]

Nothing that readily stands out. Good idea to remove the castle nut and the delrin hub/sleeve from the prop for closer inspection.

[stevechumo]

I decided to get a new hub on <READ ANNOUNCEMENTS> anyway. There's some little play between the metal hub and the polyurethane hub. I think it's worth the change. :)

[stevechumo]

After I replaced the prop hub, the issue was still there. I took it to a boat shop. The mechanic held my boat for a month. He told me that it's overheating after I called him a few times without him returning my call. I paid for his diagnostic fee, and bought the water pump kit. I replaced the water pump and the issue was still the same. I then replaced all 3 fuel pumps. It ran better, but the power still got dropped for like 15 times during an 80 miles trip. I then replaced the TPS, and it ran extremely well. It seems to me every replacement of parts just makes it better. :)

[EuropeanAM]

Hate that you had to throw all of those parts at it to get this far.

One thing I didn't see above, but i suspect to be the case: When the power was limited to 3000 RPM's, were you receiving Warning Horns and/or Warning Lights?

[stevechumo]

I didn't receive any warning horn or light. That's why I called it a ghost. I asked the shop to scan the ecu, but he didn't do it.

[EuropeanAM]

Pity... likely would have found the root cause a lot sooner.

Glad you're running again, though!

[stevechumo]

Pity... likely would have found the root cause a lot sooner.

Glad you're running again, though!

Many thanks. Happy Thanksgiving!