1978 23 sceptre inboard speed

[fredetzel]

I have had this boat about 12 years and the speed seems a little slow from what I have read. The engine is a 350 marine power with a velvet drive trans. At 3000 rpm 21 mph. At wot 3700 rpm 25 mph. Is this about right for an inboard or is this too slow.Thanks

[yankee]

I think you are about 1000 rpm light for that engine.
Have you got a fuel line restriction someplace?

[Hookdude]

I agree. Seems like you're not getting enough fuel.
That engine should be near 5K at full throttle.
Throttle cable adjusted properly?
Restricted fuel or vent line?
Weak pump?
Carb dirty or misadjusted?

[fredetzel]

Ichecked the tach it's good. checked the fuel filters there good fuel press and volume are good at idle not shure about full throttle. The spark advance weights and springs look a little rough but I ran out of daylight I'll look into it moor this week end. thanks for the imput your help is appreciated.Iwill post what I find this week end.

[ericminnig]

What size prop do u have? I have a sceptre with a fresh 350ci. prop size is 16x19. I run 2800 rpm ar 24 knots. At 3200 i'm 28 knots. good luck

[Gary Hill]

Check my previous post, I have a differnt prop then you and run 27-28 at 3200 with 315 HP.

[JohnB]

Tach might be off a tad, reading low.
Most imboards I have been on with similar setup cruise at about 24 and top out at about 30-32. The inboards are not speed demons, but they ride GREAT.

[riprunner]

At 3000 RPM's I'm getting about the same cruise speed as you on a 23 inboard CC with a 350 as well. The speed has been my only gripe with this boat. Also, I would like to note that I usually run with full tanks, ice, tackle, and enough rods for 3 boats so they are real world numbers. The rough water ability and dry ride is second to none, but man is she slow! The boat is also very affected by weight, everytime you add another person it really slows you down. My outboard center consoles have not been affected by weight nearly as much. I should have gone with a diesel.

[MarkR]

Mine is a '75 Sceptre inboard, Marine Power 350 - 4B Carb 260HP

16 x 16 cupped

2700rpm - 20knts (most economical cruise - I think)
4000rpm - 30knts