New toon. 90Merc @ 7000 RPM. WAY to much rev?

[Racin929]

New toon, Encore bentley 220 cruise. Setup is 90 merc, no strakes. I get about 22-23mph at 6000. but engine revs to 7000 were I get 26-28mph. ( I get 25-26 with 1100lbs loaded @ 7000rpm) I called the dealer and they said thats way to much rev. I looked and snapped some pics, the prop shows 14 x 13p. What should I do? I DO NOT want to loose any speed. what prop should I let them replace this one with?

[Bryden24shp]

Your not gonna loose speed by pitching up, you should actually gain some. Going to a higher pitched prop is like going to a lower rear gear ratio in a truck, your gonna drop some RPM's and should go alittle faster. At 7 grand, you should be into your rev limiter. By going to a higher pitch, you'll be grabbing and pushing more water behind the boat. I would try a 17 pitch and see what happens. Should drop 400-500 rpms. Keep us posted!
Good luck with it!

[Bryden24shp]

I'm sorry, By the way, NICE BOAT! Congrats!

[Racin929]

So more pitch but NOT more prop? The dealer was saying like a 14.5 prop and 14 pitch.

And thanks!

[kryptonite]

I would think that 14x13P would be about right with a 90hp. But 7000 RPM is not ok.

I have a 22' 75hp four stroke running a 14x11p with extra cup. Although under light loads I run a little high on RPM's (6,000), but under heavy loads it's propped perfect (5,500).

How many people on the boat?

How much gear do you have on board?

I'd be curious if the prop you have has extra cup or not. Although 7,000 is way too high, don't think load will change it that much. Kind of like my scenario you might see a 500 RPM variation depending on load.

[DRock]

13p sounds about right for your set up. Mine is propped about the same. I would think a rev limiter would come in before 7k rpm? Does your tach stay pretty consistent? The reason i ask is my tach will have a mind of its own first thing in the morning. It will read fine until about 4k rpms, then jump up 1000rpm. I tap the tach once and it comes down to where it's supposed to be and will act fine the rest of the day.

I know your toon is new, but anything is possible. If you truly are running 7k rpm, i would suggest a 15p. Your 13p should be turning about 5800-6200rpm unless you have a very strong 90.

[Bamaman]

You should run the boat by the dealership and get them to checkout the tachometer.

You should be hitting the speed limiter by around 6300 rpm's. Your performance is pretty good, and I suspect there's a tach problem.

[wwind3]

I had to go to a 16 pitch aluminum--still will redline at 5800. I have a stainless I pitched up to 17 that tops out around 5500---BUT the aluminum prop at 16 is 1mph faster---whoodathunkit? It's a crapshoot I guess.

[Bryden24shp]

It's a crapshoot I guess.

Yep, propping is always a roll of the dice. Its fun to play with them.
Racin929-Take notes on your props when you run them. Note the top RPM's, Top speed, (GPS) and rate the holeshot on a scale of 1 to 5, bow or stern rise. If you have any speculation your tach is off as Bama said, get it looked at. Looking at your pics, you may want to look at your cav plate while running WOT to make sure you are in the water deep enough. It looks like it is mounted high on the transom with no holes left to lower it. May be a concern, too. But at that RPM you should be well into the rev limiter. When you hit the limiter, you'll know it, the cylinders will cut out and you'll hear the motor's exhaust tone change.
I also have to note fuel consumption, in gallons used per hour. I have a fuel flow meter that I use. Time to plane out, RPM's vs MPH through the entire RPM spectrum in 500 RPM intervals. Best cruise speed and RPM's and fuel GPH . And any other conditions, load, water conditions, temp. I also have to keep the fuel tank levels and weight load consistant. If you want to gnats ass precise, you can do this as well.
But the main thing is to... have fun with it!

[Racin929]

Thanks. I will discuss all of this with the dealer. Ive been in the water for the last few days and am as red as a tomato. Soon as im able to take it to the dealer I will. I will keep all posted. On a side note, I never heard the rev limiter, So im thinking its the tach as well.

[megawatt]

Your tach may not be compatable with your motor/alternator configuration. Usually there is a selector switch on the back of the instrument, and yours may have been incorrectly set up by the dealer.

[1roadking]

It has to be the tach. Your prop size and speeds sound perfect!