Thor39

Hey guys.

So our 39' Ocean Express build is finally wrapping up. I've gotten about two hours of run time on it and have been getting used to how it handles. The boat likes to weave left and right below 55-60 mph. Once the boat really gets moving, it's almost on rails though. Is this normal? It will have water spray coming up between the sponsons when it is in the darty stage which suggests to me that its too bow heavy at that point?

Also, anyone have insight on props? It has Arneson 1600s on it. I've heard people on all sides of the spectrum from 16.25" props to 18" props. I have cupped 16.25x34p and it has done well but I wonder if it would work better with a larger diameter prop. It seemed to spray a lot of water vertically. So far, we've done 86 MPH at 5000 RPM but I know it has a lot more in it with dialing in the drives, trim, and props. It makes right around 1000 HP per side and they're brand new mills done by Frank @ Scorpion.

Lastly, it has power trim and it's a struggle finding out exactly how it wants to be run. Seems to vary a lot by speed. Also, I wonder if the darting has something to do with the toe in changing based on the trim height of the arnesons. Just how the geometry is setup.

If you all want pics/videos, I can see about uploading some. I don't think anyone has seen this boat on this forum for 8+ years. Hoping to have it at Boyne Thunder in July if I can get it running really good.

Thanks,
Ross

DrFeelgood

No experience with that hull -- but you're describing "bow steer". Too much trim tab, too much weight in the bow, negative drive trim, all can contribute.

KNOT-RIGHT

props spinning in or out?
to my knowledge 1600s did not have counter rotation. so you have a counter rotating engine?
spinning out will lift stern /bow down. spinning in will pull stern down /bow up.
19 spline shafts? more diameter should create more stern lift.
post a picture of boat on trailer of the business end.
if the 1600,s are trimable mark on indicators on dash where they are set at parallel to the aft running surface and start there.
have you tried calling OE?
Just some things to try.

bws

When I had my 39 OE it didn't weave at lower speeds, but it wasn't as responsive to steering input. It wasn't problematic, you could cruise around all day at 45 MPH if you wanted, but it had a heavier feeling to the steering and reacted slower....the boat started getting more responsive above 65 and really seemed to be happier at 70-75. My boat had 1600's, with fixed trim, 4 blade Rollas 18x32, spinning in. What steering cylinders do you have on it? Originally mine had the Hynautic, I was much happier with it when we switched it over to Zeiger. At slower speeds I would get the spray back out of the tunnel, the water is hitting the back of the tunnel and getting kicked back out the front. It's not an issue at all, it goes away with a little more speed. You might want to start a thread in the OE section, there were quite a few members that had 39's, just not sure how often they check back in.

Thor39

Correct, I have a counter rotating engine. Props spin inward on these. They're 19 spline but I run brass adapters for #6 drive props. I've had Ken @ ACM look at the drives and tell me where to run them. I'll have him re-set everything before next run. I also spoke with Focht from OE a few times about the boat but wouldn't hurt to do so again.

Not sure on steering cylinders, I will look at them next.

Still looking for as much info as I can. Thanks a lot guys.

bws

If you have Kenny setting up the boat, you are in good hands!

Thor39

Did a quick look at your post history, did you happen to own Swift Kick? I know Brandon just bought it through ACM. Never got to look closely at it but I know it was one of the foremost 39s out there.

Still waiting on trim rams from Yates and then it's going in the water. Now to find some 18" props...

bws

Thanks for the compliment....I did own Swift Kick for about 14 years. It was always taken care by the previous owners, it went thru a major restoration while I had it and then Bob (who I sold it to) made it even a little bit nicer. That boat is in great shape! I don't know Brandon, but I hope he enjoys it!

I hope you get your trim rams soon and get to enjoy your summer on it!

mikefili

I do know you asked for input from someone who has past experience with that hull, I have not, but have much experience in cats. I did throttle an 32 Active Thunder Cat which in many ways very similar to an Ocean Express. the Bow Steer or weaving as you describe is very common among cats that use less aerodynamic lift and more hydrodynamic lift. what you are experiencing is the boat is not packing enough air at slower speeds and needs more speed, to settle on the air pack. you will find that that boat will run faster and feel 100% better if you run it into the wind on a windy day, the more air the boat packs the better it will handle, I think once you get above 65 or so, say 80 and up it will come alive.

Thor39

Thank you and yes this seems dead on to what I've found. I had a day when I was running up river, into a stiff breeze and the boat was very happy.

It's a bit hard to push it up to those 75+ speeds where it drives really good when it is white knuckling getting up there. When you don't move the wheel at 55 mph but the boat diverts 20 compass points, it's a bit annoying. There's gotta be something I can do to help get some more lift earlier on.

Any feedback/input is appreciated!