Motor dropping back from WOT...

[Swamp Rat]

I ain't the most mechanically inclined dude in the world, so this baffles me. And I'm hampered by not having an operating tachometer on the boat.

I took the Sea Pro to the lake today to run it for a while, after it had been sitting in saltwater for the better part of a week. Got it out of the no-wake zone, let it eat, and, after adjusting trim, it settled in at a WOT speed of about 40 mph. This is a 2003 (I think) Johnson 140 hp 4 stroke (Suzuki engine, actually)....

After a bit, I sensed the RPMs dropping off a bit, and speed dropped back to 38. The throttle was still WOT. This went on for a while - it would recover, but at one point dropped back to under 30. I was sometimes going into the wind, sometimes into chop, didn't know if that had an impact or not. I can understand losing speed under different wind and surface chop conditions (duh...) but why would RPM's drop back?

[mhogancu]

Check the air box, I had the same problem with that motor, come to find out a bird built a nest in the box and it was starving for air

[JOHNSON]

Water in fuel? Do you have a water separator?

G

[Swamp Rat]

No water separator - I am getting one installed next week.

MH, I'll check that.

[Rubberhead*]

No water separator - I am getting one installed next week.

MH, I'll check that.

That was my first thought too. The other thing might be the water pump is working but not 100% and your getting enough heat to restrict the fuel flow.

[Swamp Rat]

That was my first thought too. The other thing might be the water pump is working but not 100% and your getting enough heat to restrict the fuel flow.

The water pump impeller was just replaced - but I did get the foot into some mud at Edisto a couple of times last week.

[Tater]

Does it come back on it's on?

[BigBrother]

Water in fuel was my first thought.

Second, is trash in the fuel.

Checking it's air source is not the worst idea either.

[Swamp Rat]

The filter is going on, regardless. They were supposed to put it on last month, but there was a "failure to communicate". I will check under the cowl for bird nesting crap in the intake.

I'm supposed to take my son and his GF shark fishing in Charleston before he heads off to college next month - I want it running smooth when I do.

I'll swing by and see Buddy tomorrow.

[Swamp Rat]

And, after the season, I'll be getting some ideas for Columbia area folks that are good and reasonable on gel coat repair. Someone must have scraped me in the marina. Not bad, but about 1/2" wide and about 3 feet long.

[scduckhntr]

Is the bulb going flat at all when it is dying out?

[Swamp Rat]

No bulb on the boat. Fuel injected.

[Swamp Rat]

Does it come back on it's on?

It seemed to go through cycles. It may also have been my imagination, but I think it would "trigger" if I hit rougher chop or went into a turn at times. I was trying to figure a pattern. Except for the one time that it dropped way back, it wasn't dramatic... more like going from a max of 40-41 mph down to about 37. But you could hear the change in the engine and "feel" it.

I'm thinking I need to run all this gas out of the boat. It's ethanol free, has Sea Foam in it, but some of it is old. If I get the gas run out, is there a way to get the tank cleaned out economically/effectively? I'm concerned now about debris in the tank, since BB brought it up.

[Tater]

did you try to trim it up any after it died off?

[Tater]

Especially since you mentioned it did it when you would hit rougher chop. Like maybe a "weak" cylinder leaking down.....

[Goin Coastal]

No bulb on the boat. Fuel injected.

It should still have a bulb. It is fuel injected but does not have an electric fuel pump. Marine Pro for your gelcoat issue.

[Swamp Rat]

It should still have a bulb. It is fuel injected but does not have an electric fuel pump. Marine Pro for your gelcoat issue.

Hmmm ... ok. I'll dig into it tomorrow. I know that, when I switch it on, there is a whirring sound like a pump priming it up before the four indicator lights go out and the signal goes off once. I assumed that whirring sound was a fuel pump.

Thanks for the pointer on Marine Pro. They are already familiar with the boat. I know they (like you) have a background with Sea Pro and I like working with them.

I am hoping this is a MINOR issue. But I want it to be right.

[rp]

No water separator - I am getting one installed next week.

MH, I'll check that.

You can do that yourself.

[Swamp Rat]

I could, but I want to make sure I get the right one. It will be mounted under the rear deck, not exposed. I use Buddy's Marine in Lexington - he's good, reasonable, and pretty quick on turn around.

The motor needs a new prop, too... so I will be seeking advice on pitch and such. The aluminum one on it is showing wear, and I know I can squeeze more out of the boat with a good stainless wheel on it.

[BigBrother]

Stainless Racor.

go to West Marine, buy it. Pull your boat to my house. Bring the flounder light.

It will have it in your boat in 10 minutes.