Hi Rik, thats what I thought. The RPM almost did go to 4.000. I have to look it up, but I think thats to high for Yanmar 6LY440's? Speed was arround 50 mph, but it felt faster, don't know if the meter is correct, have to double check. The boat used to hold 40 people and I think the props are chosen for that kind of weight.

Looked at the manual, the engines high rpm is 4.200. Think they did that.

So I guess a higher pitch would be the way to go? Heard about a company in Miami that can bend the props to max 2 pitch higher, any experience with that?

Your going to need some larger propellers.

The Yanmar 420/440/480's are a 3300 rpm engine.

Are you going to use the boat for yourself or to carry passengers?

I'm going to use it for myself and my family. Will not be carrying around a lot of people with it like it used to do.

So basically you say go larger in size? They are 17.5 now.

What's the reduction ratio? Pitch?

Have you tried the rotation inboard instead of outboard?

The gears have a reduction ratio of 1.15 and the pitch is 22.5.

I have not tried the rotation change, would inboard be better?

Call Frank and Jimmies in Ft lauderdale, ask for Mike Eggleston he can tell you what can be done. But I agree with Rik you need bigger props, if you are spinning a Yanmar 440 to 4000RPM you are going to blow it up.

I have Yanmar 6LP's and they can spin to 4000, the recommended RPM with a full load is 3800. The 6LY's are a bigger motor and are not designed to spin as fast. 3300 as Rik said, if you get 3400 or 3500 with a very light boat in perfect conditions that is ok, but with a full load you should always be able to reach 3300 or you are overpropped.

Post some pics of it in the water!

I agree, it didn't feel good so many RPM. I will see what I can find here to test a little with size and Pitch.

Who made these originally? Looks like an airborne hull?

Originally it's a Skater hull. Skater sold the mold to Thriller and they extended the mold(I think) 9 foot.