Spun Hub? And new prop recommendations.

[rhgoudeau]

I've got a 1996 Ranger R70, 17', with a '96 115 Mercury (hull rating is 130hp). I'm running a Quicksilver Lazer II 22 pitch (48 16992 A40). Hull weight is 1100lbs, plus normal load of about 700lbs (2 people, gas, tackle, etc). When I first got the boat (in 2001), it would run about 46mph at 5200rpm. About two years ago, I raised the motor 1 notch, trying to get a better hole shot. Since then, I feel like the top speed has been dropping off. Last time out, I've was turning 6200rpm, and could only get up to 38mph (GPS). Also, at times I couldn't get up on plane, and it felt like I was bogging in mud.

I am going to get the prop checked this week, to see if I've got a spun hub, but the real question is, would a prop change help my top end. I see people claiming over 50mph with this hull/motor, and I've never gotten anywhere close to that. Actually, unless the boat is completely stripped down, it has never run up on the pad.

 

[steelespike]

Re: Spun Hub? And new prop recommendations.

If you had a spun hub the motor would rev and the boat very likely would actually slow.
Usually as the motor would reach a certain power the hub would slip and the motor rev and the boat slow.
also usually you would have to slow to get the hub to grab. Did you raise the motor one notch(hole) vertically?
You may be having slight ventilation. you should start be lowering the motor to its original height.
Is the prop clean and in good condition?
You also may want to verify the tach is accurate. If its really at 6200 your way over the rpm rating of 5250.

 

[rhgoudeau]

Re: Spun Hub? And new prop recommendations.

Yeah, I wondered about the tach, but the overall speed has dropped also. The prop is in good condition. When I originally raised the motor (vertically), the rpms did not increase dramatically. The Ranger has a built-in 6" setback, and the vent plate is only maybe 1" above the bottom of the hull. I can lower it back, but itAny other ideas about the sudden rpm increase?