Top speed, cutting out or hesitation

[carlsonwa]

My guess, is you are hitting your rev limiter. Compare you RPM when it is surging to the manual for your engine. I experienced this when I pick up a new prop last year. Had to have it cupped a bit more by OJ.

[JimN]

Originally Posted by nrojay

what do you think would this much weight have any bearing on top speed?

Boat hulls aren't efficient when it comes to the thrust from the prop, meaning, it takes a lot to get it to move horizontally because of the drag on the wetted surface. When a boat is on plane, not much of the hull is in contact with the water and that means it can accelerate a lot faster. When the hull is displacing more water due to added weight, it takes a lot more to get it on plane. Also, since the prop is pushing against water, which moves out of the way pretty readily, it's a balancing act WRT selecting the correct prop. If the prop is too aggressive, the engine will bog under load and if it's not aggressive enough, it will cavitate. Even at speed, the water is trying very hard to slow the boat, so you won't reach the typical top speed for this boat unless you add a lot of power and prop.

[nrojay]

Ok just pulled into drive after an awesome 8 hours on the water in Broken Bow, OK
The weight was the problem it ran out at 48mph GPS. However it still kinda surged a little at top speed like a horse trying to run back to the barn. I will clean the fuel screen and change fuel filters this week. WOW I LOVE MY BOAT !!

[JimN]

Originally Posted by nrojay

Ok just pulled into drive after an awesome 8 hours on the water in Broken Bow, OK
The weight was the problem it ran out at 48mph GPS. However it still kinda surged a little at top speed like a horse trying to run back to the barn. I will clean the fuel screen and change fuel filters this week. WOW I LOVE MY BOAT !!

What is the temperature after it has been running for a while? If it's still 120°, you need to address that. If that's as high as it gets, I would guess that at least one of the thermostats was removed and that's not the way this engine was designed to be run. It also wastes a lot of gas because a cold engine is never efficient You can't possibly burn all of the fuel being delivered at that temperature. Best practice is to connect it to a diagnostic computer and see the info that's going to the ECM, not the gauge on the dash.

[nrojay]

it was running at 160 all day long

[FrankSchwab]

What RPM are you at when the engine is surging?

With 1150 pounds of steel and lead in the boat, it's likely the previous owner put a prop on the boat designed for wakeboard speeds, which means that you'll hit the rev limiter when going fast. You can choose to either pull the throttle back a bit to keep the engine off the rev limit, or buy a new prop that will keep the engine from hitting the rev limiter.

/frank

[nrojay]

You know I think ill just hold back on throttle for now, I can barefoot, slalom, wakeboard, kneeboard and tube just fine like it is and look for a deal on a prop in the future.

This hull design is awesome on slalom virtually no wake before removing all the steel, I was plowing hard into the wake.

Good news is Steel prices are good I can sell this steel and maybe put a good bit on a new prop!!

[cptskier15]

Read the whole thread and not a single photo of the boat :P

[Stx221]

Originally Posted by cptskier15

Read the whole thread and not a single photo of the boat :P

It's sad, really. He has 9 posts and no pictures! We don't even know the color scheme of the gelcoat... Hopefully he changes that.

[nrojay]

ok if someone will explain how to post a picture ill do it