only 5.5 MPH with my 9.5

[Philip_G]

I wasn't expecting a speed demon, but I was expecting closer to 10mph.

boat: 14' tracker tinny, has a floor, had 400lbs of people and a couple batteries, and we're up at 5500+ feet in elevation.

I noticed at full throttle the motor was not a constant RPM, it would rev up, almost like a slipping clutch on a car, the motor would shudder on the transom and continue as before, I was thinking maybe a spun prop? But I don't know how to check. It definitely misfired in the mid RPM range, but trolled around for 2 hours beautifully.

I need to adjust the angle of the motor on the transom, it was pointing down a little and I'm sure that hurt performance

 

[ezeke]

Re: only 5.5 MPH with my 9.5

The anti-ventilation plate should be parallel to the surface of the water when the boat is on plane.

The anti-ventilation plate should be even with the bottom of the boat.

The problem with higher elevation is lack of oxygen, so you may need to adjust your idle needle and/or your high speed jet accordingly. You should consider a propeller with a lower pitch than normal at that elevation. See if there is a BRP dealer at your elevation who can advise you on the jet. I would use a 43D - # 0328539.

On that large a boat, you might try to find a 0386587 - 5 pitch propeller. Maybe sea-way.com has one. Failing that, look for a Michigan Wheel 012068 with 6.5 pitch..

 

[Philip_G]

Re: only 5.5 MPH with my 9.5

I'll set it better next time, I need a board, the transom is too narrow anyway.

the back of the boat is pretty low in the water, I'd say the cowl is maximum 5" above the water on the back edge.

the plugs don't look bad, a little oily but brown, I'm pulling the flywheel to have a look at the points and everything now

 

[CaptainHook]

Re: only 5.5 MPH with my 9.5

Probably ign or carb issue. I was running a 7.5 hp on a 14 ft aluminum last sunday, just about the same load and was at 11 mph on the gps.

 

[Philip_G]

Re: only 5.5 MPH with my 9.5

Probably ign or carb issue. I was running a 7.5 hp on a 14 ft aluminum last sunday, just about the same load and was at 11 mph on the gps.

Well, I thought so too.
I pulled the flywheel and honestly everything "under the hood" looked ok, pretty new really. I'm thinking it's probably a carb set up issue, I'll rebuild it and reset it here in a few months, I have a camping trip coming up and I don't want to risk screwing it up since it's running OK right now.

here's a pic of the ignition

 

[Rick.]

Re: only 5.5 MPH with my 9.5

Check for spark at both plugs. You might be running one only one. Best of luck. Rick.

 

[ezeke]

Re: only 5.5 MPH with my 9.5

Probably ign or carb issue. I was running a 7.5 hp on a 14 ft aluminum last sunday, just about the same load and was at 11 mph on the gps.

And at what elevation are you running?

 

[Philip_G]

Re: only 5.5 MPH with my 9.5

Check for spark at both plugs. You might be running one only one. Best of luck. Rick.

checked them yesterday, getting a good enough spark to jump a 10mm gap on both, I'll recheck and I'll try running it on just one plug on each and see.

I took the prop off and looked for any sort of number and found none, maybe it's the wrong prop or something too, it sure churned up the water, lost of bubbles.

next time I go out I'll get video of it revving up at full throttle, maybe one of the cylinders really is cutting in and out, but I can't see a reason for it

 

[Philip_G]

Re: only 5.5 MPH with my 9.5

And at what elevation are you running?

stupid altitude

at this altitude with the correction factor I should be about 7hp so comparable to his 7.5

 

[Philip_G]

Re: only 5.5 MPH with my 9.5

I just rechecked everything again, good spark on both plugs, I did just notice on the top cover, above the carb, there's a round hole in the sound insulation, and glued against the top cover in that hole is a piece of plastic, that was loose.
I wonder if it's possible the carb was intermittently sucking that down against it and choking it out a little.