Inboard, direct drive, ski-boat type questions

[QC]

I am finishing a 20' Chris Craft replica type boat thing deal . . . It is gonna be powered by a carbed 350 IB, direct drive, 1:1 Velvet Drive, prolly around a 12" x 15", left hand rotation propeller. With the exception of pitch these things are fixed.

Now to my need for noodling assistance. I do not like port helms. I do not like unbalanced boats. I do like right handed throttle control. I am using a floor shifter for forward and reverse, but I am going to use a typical Morse throttle control no matter what I do. Also, all vintage Chris runabouts that I find/see have a starboard helm which is definitely my preference. However . . . with the left hand spinning prop I am also considering a port helm due to prop torque. I can find a lot of regular tournament SKI boats (not wakers) that have left hand props and starboard helms. As I said I don't like port helms for me, but I am going to sell this thing if I can bear to as it is just not gonna be the right boat for where we boat. I'll play a little with her, but I do plan on selling her this next season if I am finished in time.

I can place battery(s), fuel, storage and other stuff pretty much anywhere I want. Does anybody have some experience in this area (driving tournament boats with left hand props and starboard helms)? I literally have never driven one . . . Will I notice much with a relatively small 12" prop (compared to an I/O) and flatter bottom? Should I just rig her the way I want? Or rig her with the helm to port (yucky) to compensate for the prop torque? Do I need to just get a life, quit obsessing and build the stupid thing and move stuff around later to get the balance right?

BTW, the Chris's I can find have right hand props . . .

 

[MikDee]

Re: Inboard, direct drive, ski-boat type questions

I don't like left hand helm's either, it always seems the waves, & spray, comes in from the left, or port side. With a left hand prop, your boat is gonna pull to the left under power, (more of a reason for a right hand helm). I think you would have a double negative as far as handling with a left hand prop, & helm, (irregardless of bottom design, or drive system). Most boats are RH drive, & RH props, & pull to the right. By the way a 12" prop is not so small, because the blade area, & small hub design gives you a lot of thrust,,, watch out for reverse, if you've never driven an inboard,,, the boats gonna go whatever way it wants, no matter which way you turn the rudder,,,lol,,, you'll see. It's best to figure that the prop will pull it to the left, in reverse, because it's LH drive, and the prop scoops water that way. I had an old 18' Higgins with a 135hp greymarine direct drive that had was RH helm, and RH drive, the prop was a 12"x12" direct drive, and it would do the max I think 4000rpm, and 38mph, when I could keep it afloat with all the leaks. Going in reverse the 1st time, was a rude awakening for me , because I only had outboards previous to this. I would hafta put a RH Helm on the boat, for my sanity, esp. with a LH prop. Also, let me ask where you got your prop sizing specs from, it sounds like Too Little pitch for a Direct D. 350 that has a lot of torque, & rpm available, I'd suggest you recalculate the design specs, because you won't be able to do much changing later. After all I was running that 12"x12" prop on only a 135hp Gray., and hitting 4000rpm. One final thought, you won't like that semi vee bottom on a heavy chop, unless you're idling, or at displacement speed, planing off will take the fillings out of your teeth! That's why I sold mine (it was so pretty too, with mahogany stained sides, & a white top, & bottom). Good Luck, Mike

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

The 15" pitch with a 1:1 means the prop is also turning WOT RPM, I calc right about 4800 - 4900. Even with 20% slip that's 55ish . . . Since it's now on topic, what kinda slip shoudl these type of boats see. It is not a tournament boat, infact this style hulkl was what Chris raced back then ('40s) I think. It was called a "Racing Runabout".

One final thought, you won't like that semi vee bottom on a heavy chop, unless you're idling, or at displacement speed, planing off will take the fillings out of your teeth!

Why do you think I don't own one . . . I have driven inboards, just not a small tournament style, basically cause unless you are a tournament skier they are flippin' stupid Thanks

 

[MikDee]

Re: Inboard, direct drive, ski-boat type questions

When I was a teenager, a friend, of a friend, had a boat like yours, an all mahogany double cockpit Chris Craft runabout with either a 95hp, or a 105hp? Chrysler inboard I think it was, I always admired it, and also wondered why it ran bow high all the time? But it was still fast for what it was, back then (the late 50's), it did maybe 36mph. I finally got a ride in it, and loved it! but almost got thrown out of the rear cockpit by the rough chop.

I know what you mean about direct drive, 1:1 ratio, and I used 20% slip to figure my top speed on the Higgins also, I forgot the max rpm, (maybe 4400) but I know I came up with 38mph.

Regarding props, with my example, I would think, even a plain vanilla 350 Chevy 4bbl. motor would easily turn up more then 5000rpm with that prop, unless you're not gonna run it at full throttle? don't you want to prop it down to peak out at 4600rpm WOT, like most marine engines do?

 

[DJ]

Re: Inboard, direct drive, ski-boat type questions

QC,

Put the helm on the S'board side. You are reselling this thing and people are used to seeing S'board side helms. Port helms look weird to the average boater.

There are lots of ways to combat prop torque (many of which you have mentioned) but I really don't think it will be an issue as evidenced by all the other ski tractors out there.

 

[180shabah]

Re: Inboard, direct drive, ski-boat type questions

Dude, where's the pics?????

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

Sorry 180shabah man . . . I have some pics posted around, here's a sampling:

This is my target look, the sides have to be painted, builder flipped up when glassing. I think I like this look anyway. The deck will be the mahogany above, but with traditional caulking "grooves". Mine is a mid-engine, direct drive, double cockpit, the one below is a V-drive, rear engine . . . it is built in Canada and carrys a $150K Canadian price tag!

 

[Cptkid570]

Re: Inboard, direct drive, ski-boat type questions

I now have to dry drool off of my keyboard...
SWEEEEET!!! (except for the photo with all of the parts scattered everywhere.. that gave me a little bit of anxiety! hahaha)

 

[tommays]

Re: Inboard, direct drive, ski-boat type questions

The Correct Craft has a right hand prop and NO real issues OTHER than it is much better to walk into a Dock on PORT it is much harder on starboard



Tommays

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

except for the photo with all of the parts scattered everywhere.. that gave me a little bit of anxiety! hahaha

Luckily, that pic is from the guy I bought it from's lawn . . . When I picked her up, all of the stuff was boxed etc. All that I need to buy is paint; epoxy; more epoxy; and probably a little more epoxy; wiring; gauges (I got a bunch of vintage gauges, but I am going to sell them); senders; the wood above (now in my garage); some plywood for seats and flooring; steering, shift and throttle cables; and a bunch of zip ties; well and maybe some more epoxy . . .

Actually, the guy advertised her as 90% complete as far as parts are concerned, and he was right. It is amazing how much I got, linkages, sea water strainer, gate valves, stuffing boxes, it goes on and on. Cleats, flag pole thing, motor mounts, mounting hardware . . . flippin' deck horns, exhaust trumpets, throttle control, floor shifter etc. He even called me last week with the best thing yet . . . Epoxy!!!!

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

The Correct Craft has a right hand prop and NO real issues OTHER than it is much better to walk into a Dock on PORT it is much harder on starboard

Yeah Tom, I guess I see a starboard helm and a right hand prop as "correct". Like an I/O or OB. This one has a left hand prop . . . And I understood that Mastercrafts and some significant others were also that way (LH prop with starboard helm). I would guess that if you are piloting one alone and make a hard turn to starboard, she could stand up on the rail pretty high. Maybe the flatter bottom than I am used to helps to solve that . . .

 

[steelespike]

Re: Inboard, direct drive, ski-boat type questions

When I was a teenager, a friend, of a friend, had a boat like yours, an all mahogany double cockpit Chris Craft runabout with either a 95hp, or a 105hp? Chrysler inboard I think it was, I always admired it, and also wondered why it ran bow high all the time? But it was still fast for what it was, back then (the late 50's), it did maybe 36mph. I finally got a ride in it, and loved it! but almost got thrown out of the rear cockpit by the rough chop.

I know what you mean about direct drive, 1:1 ratio, and I used 20% slip to figure my top speed on the Higgins also, I forgot the max rpm, (maybe 4400) but I know I came up with 38mph.

Regarding props, with my example, I would think, even a plain vanilla 350 Chevy 4bbl. motor would easily turn up more then 5000rpm with that prop, unless you're not gonna run it at full throttle? don't you want to prop it down to peak out at 4600rpm WOT, like most marine engines do?

Usually the smaller old Chris Crafts Had a Chris Craft motor Based on the Hercules industrial motors.I believe
a model K Smaller boats usually had this 6 cylinder 95 or 105 hp @ about 3,600 rpm.There was also the model B that was a 45 hp 4 cylinder.This was usually the entry level motor on the smaller boats.
Chris Craft did build many boats like the cockpit forward in the picture;
and these were straight drive this did result in the bow tending to be high
though not the sole reason.My self and friends had 3 of these through the years among other straight drives.Lots of fun,terrific low end torque,and pretty good speed for the age of the technology.Also pretty trouble free.

 

[tommays]

Re: Inboard, direct drive, ski-boat type questions

For what ever reason they used reverse rotation motors with a gear reduction of around 1.25 to 1.5 with right hand props until they just had to switch to standard motors


We will see about the speed BUT i am taking the POOL# that you will start to hit the speed wall around 48 MPH




Tommays

 

[MikDee]

Re: Inboard, direct drive, ski-boat type questions

OC, That boat is a real Honey! I've got a soft spot for those old Mahogany runabouts, here a sample pic of The Higgin's speedboat I had, mine wasn't in as good a shape as this though:

http://smg.photobucket.com/albums/v...current=17ftHigginsSpeedboat135Greymarine.jpg

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

i am taking the POOL# that you will start to hit the speed wall around 48 MPH

I thought so too Tom, but these are not tournament boats . . . All of the guys over at glen-l dot com are breaking 50 with small blocks in this hull (Monaco) and the next one up (Riviera). One knucklehead is claiming 70 "radar", but I can't/don't/won't believe that That's why I am asking about slip % with these. I have a hard time even writing 20%, tournament boats must approach 30% with what I agree is about a 48 MPH "wall"

 

[180shabah]

Re: Inboard, direct drive, ski-boat type questions

Gotta agree with cptkid - that thing has got me droolin'...

Can't wiat to see it as the restoration continues.


You say it is a Monaco - I have had my eye on the Gentry, smaller and totally impractical, but good lookin' and should be a blast on the water.

 

[QC]

Re: Inboard, direct drive, ski-boat type questions

Yeah, it's definitely a Monaco it has just never been finished. 1st guy built the hull and then when it came to the deck he got stupid and used furniture type paper veneer . . . Disaster. The 2nd guy was going to do what I am doing, he acquired all of the pieces, the engine and trans etc. and then burnt out before he sanded, epoxied, knuckle busted etc. I just finished re-coating all of the epoxy inside the hull. Then I am gonna flip her and tackle the bottom and sides, and the trailer. Trailer needs help, but I have a decent plan there I think. Most think I am nuts but I am targeting May1st . . .

Anybody know a good chrome shop in SoCal?

180dude, I like the Gentry too, but like you said, impractical. Here is an almost perfect Monaco:

 

[180shabah]

Re: Inboard, direct drive, ski-boat type questions

I am envious of your project - I lost my garage when we moved 2 1/2 years ago.

I am "patiently" waiting until I can get started on this

Unfortunately it will be several years before I can start - Renovation of our 1903 Victorian is getting all of the free time, and of course I'll be building the Garage'majhal before starting a boat.