Propulsion Problems

[brianm132]

Hello List,

I have a 1979 C&C34 with a two blade feathering prop. Just purchased it 17 months ago. I have not done much motoring, mostly sailing. I've used the motor pretty much to just get in and out of the slip. However, I recently noticed that when I get the throttle to about 1/3 that is the maximum speed. I can push it up beyond 3/4 and not pick up any appreciable speed. I'm wondering if the issue is the prop or the timing. I'm having a short haul done soon (hopefully this Saturday) and I will check the prop, shaft and bottom. I plan to play with the distributor over the next day or so. Does anyone have any advice or have experienced the same or similar issue. Any help would be greatly appreciated.

Brian
S/V Rekofa
C&C 34

[Will Jacocks]

Basically, you're not going to get much more than that. Displacement hulls take a lot to push beyond a certain speed and you really don't need to push more than 1/3 throttle as it just becomes more and more inefficient past that point.

[wlevin]

Brian
Given the way linkages work, and how variable the setups are, 1/3 throttle could mean almost anything. It would help to know your speed through the water (in still water) and rpm's to know what your situation is. If 1/3 throttle gives you 2000 rpm and 6 knots through the water, no wonder more throttle doesn't make your boat go faster. But if 1/3 throttle means 1400 rpm and 4.5 knots, there is a problem somewhere if more throttle does not increase boat speed.
Bill and Jeanne
T34C #453
Otter

[msmith10]

Will and Bill are right. What is your boat speed and RPM when you're at "1/3 throttle"?
For instance, my boat will top out at about 6.2-6.4 knots at about 2000 rpm. Opening it further does nothing.
I can do about 5 knots at 1500 RPM, and this is where I tend to cruise, since the fuel consumption is a lot less for little loss in speed.

[Maurice]

Hi Brian,

My friend removed an atomic 4 from a C&C 34 two years ago. He too was not impressed with the performance. He couldn't get off the dock in a blow. Being a marine engineer he wanted his diesel...and he got one. I bought the A-4 from him and it is now my spare...perfect engine.

The setup I got from him has a reduction gear and it should have pushed that boat to hull speed no problem. Not sure what he was using for a prop.

Give South Shore Marine a call in Canada. Some of the guys that work there built those boats. They will have the specs and they know their stuff.

http://www.niagara.com/sailboat/about.html

Good luck with it.

[brianm132]

Thanks for the feedback. I'll have to check my speed next time out. I do not have a tachometer however. I too had trouble getting out of the slip two Fridays ago in a bit of a blow. My fenders were behind a piling which I thought I should have been able to power through. No such luck. I'm taking her for a short haul on Wednesday and a clean bottom may show some improvement. I'll keep you posted.

Brian
S/V Rekofa
C&C 34

[Dave Neptune]

Brian, for what it is worth I am pushing a 35 footer and I am at max cruise at about 1/3 open and get no more out of her after about 1/2 way open.

Dave Neptune:cool:

[joe_db]

My friends had a C&C 34 with the factory Yanmar 2 cylinder diesel. My C&C 35 with the A-4 would pass them like they were aground when we did a "powerboat race" :D
My ancient-beat-to-crap-about-to-be-removed engine still hits 6.5 knots as of a few days ago. You have an issue with either very low power or a prop issue.

[brianm132]

Taking her for a short haul tomorrow and will check speed and prop while I'm at it.

Thanks