90HP Yamaha won't plane my C-Dory 22

[C-Dog]

I am a new C-Dory owner, but not new to boating. In March, I bought a 2003 22' CDory Cruiser with a 2011 Yamaha 90HP 4-stroke motor. Motor is still under warranty and, according to our mechanic, had only 20 hours on it when we got it. Had to put motor in shop so mechanic could verify motor condition so we could transfer warranty to me. Everything checked out on motor as great condition. But, I have fought one problem after another since then. I discovered the last owner did not maintain boat and that the gas tank was full of dirt and debris. So fuel lines were all fouled. I exchanged all lines between tank and motor, cleaned injectors, changed all filters (oil and fuel), and finally got motor running great - for 1 day. With just me and the wife, got up on plane and was running mid 20s and up to 30 with no problem. Next day, with full load, boat would not plane. I figured we were just overloaded and didn't worry too much. The following day, the boat still would not plane with just wife, me and ice chest (which I put in the front of the boat to try to plane). Ice chest, that is - not wife. I run the boat in the Mississippi Sound and both days there was very, very light chop. The prop is 13.4 X 15 which sounds like what it should be from reading other posts. Anybody have any ideas why I can't get the boat on plane?

[BrentB]

Is OB running ok ?

rpm increases but boat speed does not

It might be a spun prop

maybe provide more info on how the OB is currently running

and have it scanned for thrown codes

[thataway]

Two identical threads--we have to decide on one.

I am betting on bad fuel--but Brent's question is good, and easy to find out--how many RPM does the outboard reach at wide open throttle. If it spins up to 6000 RPM--spun prop. If only 2000 RPM--bad fuel tank.

[colobear]

What is max rpm at WOT? That can tell you a lot about prop size.
My bet is with Bob, make sure all filters are new, run some seafoam through the engine.

[hardee]

That and Is teh OB in the right place on the boat. Depth (anticavitation plate) at the right depth? And is the OB tilt correct, or all the way down.

What speed (GPS speed) were you running that you were not able to plane at?

Should be able to plane by 10 to 12 knots and for sure by 15.

Harvey
SleepyC

[starcrafttom]

Ensure that all the plugs are firing. My 225 lost a plug last year and i could not run top speed. With all the fooling around with the motor you could have knocked a plug wire loose or a plug may have just gone out as mine did.

[C-Dog]

Thanks everyone for your replies. Understand about the 2 threads, but wasn't sure I would get replies if I had the post in the wrong forum. Guess I didn't understand how things work, but will stick with this thread now. First, I didn't talk about cleaning the fuel tank before, but I did clean it thoroughly when I changed out all of the hoses between the tank and the motor. I also replaced the Racor filter and replaced all fuel instead of trying to clean it up. That being said, I am not sure that the fuel is still the problem, but maybe.... To be honest, I don't know the WOT rpm numbers but will get those in the next day or so when I can take the boat back out. I do know that WOT on the day it ran great I was going 26+ knots and on the next day with just my wife, me and ice chest I was going 9 -10 knots WOT. The motor runs great - doesn't bog down or miss. Now at one point on the 2nd day that I was running it and couldn't get on a plane, after about 40 minutes running, the motor sounded like it spun the prop. It revved up super loud just like the prop was gone. I checked the prop and it "seemed" to be okay, but we puttered back into harbor just in case. I have checked the prop since getting home and it appears to be fine but maybe I don't know what I am looking for. I have experience with spun props, but mostly the old ones with shearing pins. I will keep in mind the rpm test that y'all posted. I don't know if the motor is mounted at the correct height but will check that out as well. Something is keeping me from getting the speed and power I should be getting.

[BrentB]

Do you have a backup prop?

Begin by removing the propeller and examining it. Look closely at the rubber hub for telltale clues, anything from subtle to dramatic signs of failure. The hub might be twisted or even look melted. Another method is to use a ball pein hammer and a center punch. Pein a dot on the metal splined hub and adjacent on the mating surface of the propeller proper. Reinstall the propeller and go for a ride. Run the engine under load. Merely idling dockside may not flow enough torque to challenge the hub. After a few minutes remove the propeller and examine your handiwork. If the dots no longer line up, then the rubber hub is spinning in its bore.

[Sunbeam]

[thataway]

Agree, that with this information that a spun prop hub is likely. There is a rubber hub (in most props on these motors) which is pressed in place with glue. The rubber can detiorrate with time (or even sometimes when with only a few hours time on it). Thus it slips at higher speeds or torque loads. Sometimes you can find out if this is the problem by putting the engine in gear (with the ignition off, and the "kill switch" off, try and turn the prop by hand. If it moves at all, then the spun hub is very likely.

Often the prop hub will have enough "grip" to work at idle, but not as soon as there is much force or thrust needed.

We always carry a spare prop, a spare prop nut, cotter pin, and thrust washer. The spare prop for us, is the one we use at Powell and is 2" less in pitch than the standard prop. We had a 3rd prop--it is an older one, which came on the boat when be bought it, and there are some dings on the blade. We leave this in the truck. The aluminum props are only about $100 (less than a tank of fuel). We also carry a "prop wrench", plus long nose pliers, a hammer and pin punch, because of a special washer for the Honda prop. The prop can be changed from a dinghy or the shoreline. Just don't drop any of the parts! I pull the prop every few months, and check the shaft, as well as re-greasing it, with a waterproof grease.

This is the reason I also carry a kicker. I spun a hub with a whole bunch of friends on a non C Dory--I am sure it was the load, and going up to full RPM rapidly--instead of easing the throttle up properly…the boat would not move, so I fired up the kicker and we got home at 3 knots! From then on, I started carrying a spare prop (extra shear pin in the dinghy, plus a multitool in the "ditch bag" I always carry in the dinghy. (Yep, I've changed a few of these-so the oars always come along!)

Proper forum?

Good luck on the resolution of this problem. The outboard forum would certainly seem proper…but anywhere seems to get read and answered!

Good explanation of the problem!

[T.R. Bauer]

My old boat spun a prop - it was a weird thing. It would just start to get on step and then rev to 6000 rpms (or more) nearly instantly as it wasn't biting the water. A new prop obviously fixed the problem.

[Sea Wolf]

Don't throw the spun prop away.

A prop shop can replace the hub for about half the cost of a new one.

The last time I had this done, Proper Tighe in Alameda told me they lubricate the new hub and the prop it goes into with molasses or corn syrup. (!)

Good slippery lubricant that washes out to give a tight fit down the line.

Who'd a thunkit???

Good Luck!

Joe.

[texasair]

Sounds like it may be a spun prop.

But if it is not,

Try running the motor directly off of a clean 6 gallon portable tank with fresh fuel to eliminate any possible problems in the fuel delivery system. If it runs good off of the portable tank, the problem could be filters, fuel tank, fuel selector, fuel vents, fuel lines, fuel pickup tube.

Also, dirt daubers and small spider nests cause a a lot of problems in tiny places.

Good luck

[Spike]

C-Dog
It could be ethonal related fuel problem. I am saying this out of first hand expensive experiance. Saying could be.

[BrentB]

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