Re: Engine-Prop matches -- CCSSC - Chris Craft Sea Skiff Club

[ Show ]

Support VoyForums

[ Shrink ]

VoyForums Announcement: Programming and providing support for this service has been a labor of love since 1997. We are one of the few services online who values our users' privacy, and have never sold your information. We have even fought hard to defend your privacy in legal cases; however, we've done it with almost no financial support -- paying out of pocket to continue providing the service. Due to the issues imposed on us by advertisers, we also stopped hosting most ads on the forums many years ago. We hope you appreciate our efforts.

Show your support by donating any amount. (Note: We are still technically a for-profit company, so your contribution is not tax-deductible.) PayPal Acct: Feedback:

Donate to VoyForums (PayPal):

[ Login ] [ Contact Forum Admin ] [ Main index ] [ Post a new message ] [ Search | Check update time | Archives: 1, 2, 3, [4] ]

[ Next Thread | Previous Thread | Next Message | Previous Message ]

Date Posted: 18:22:03 11/03/02 Sun
Author: bob durand
Author Host/IP: cache-mtc-am01.proxy.aol.com / 64.12.97.6
Subject: Re: Engine-Prop matches
In reply to: Alan 's message, "Re: Engine-Prop matches" on 16:40:51 11/03/02 Sun

>Sorry, Faye typed it wrong, it is a 14x14 prop with a
>cup that we run on SmithSkiff. Do you run a reduction
>gear? that will make a major difference in prop speed.
hello Alan,The engines are 225hp each and new this year. they replaced 1965 Chrysler 318s rated at 190hp but operating very inefficiently. Currently, the boat operates well with crusing speed of 19mph@2850rpms and max rpms of 4300 yeild 34mph.My question iin consideration of noticable vibration in the area between the rudder post and the strut fastenings. engine (s)alignment is fine having been checked 3 times. shafts are new and checked as are cutless bearings. both sides have this vibation. it is most noticable at 3000 revs and above.could it be that cupped props wouldhelp? the props have both been checked twice by henry Smith Co. Thanks

[ Next Thread | Previous Thread | Next Message | Previous Message ]

Replies:

[> [> [> [> Re: Engine-Prop matches -- Alan, 08:13:09 11/05/02 Tue (cache-mtc-am01.proxy.aol.com/64.12.97.6)

.
>Bob. Your RPM sounds fine. On my 22skiff I did not like the sound or feel when I let the engine run much above 4000 rpm so I over wheeled to get 38/3900 rpm. I did loose some top speed put 34MPH is just fine with me. I cruse 19 to 20 mph @ 2000 rpm. It may be that your clearance between prop and rudder is not enough which could cause your problem. The second thing that could cause this is prop to bottom clearance. I am sorry, but I can't rember how to figure this clearance. I do rember the prop hub to strut should me 1 to 1 1/2 times the shaft dia.. The third thing is strut and rudder supports.. Cups should dropmrpm appox 200 rpm

[ Post a Reply to This Message ]
[ Edit | View ]

[> [> [> [> [> Re: Engine-Prop matches -- Bob, 07:21:17 11/07/02 Thu (cache-mtc-am01.proxy.aol.com/64.12.97.6)

>Alan, Thanks for the info.I have contacted Michigan Wheel and await their reply.Some of the dimensions involved are:
Prop shaft end to rudder-4 in,strut to shaft taper-aft end- 4 3/4 in.,prop tip to hull-2 1/2 in.,shaft dia-1 1/2 in.I dont know what these figures mean.In my exploring I did find that the tube steering yoke on one side is worn enough toallow the rudder to flutter quite noyicably. Does a cupped prop reduce the impact of the propwash on the hull? It seems that that clearance is close to me. Thanks,Bob

[ Post a Reply to This Message ]
[ Edit | View ]

[> [> [> [> [> [> Re: Engine-Prop matches -- Alan, 09:06:42 11/09/02 Sat (cache-rl05.proxy.aol.com/152.163.189.101)

Bob, Any slop in the steering system can set up all kinds of noise and shakes and can sound and feel like some else and some place else. In other words, slop is bad. prop hub to strut should be i to 1/2 tines the shaft dia. In other words the clearance along the shaft between strut and prop hub should be 1.5 to 2.25". There again the less clearance is better, less wip.

Cuped wheels. I may be wrong on this, but here goes. Cuped wheels are usely used on higer speed boats. They seem to give better out of the hole speed as the engine can come up to rpm faster and as boat speed/engine rpm get up the cup gives the effect of appox. 2" of pitch.

Alan

[ Post a Reply to This Message ]
[ Edit | View ]