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'62 Chris Craft 18' Holiday

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Stunoodle
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'62 Chris Craft 18' Holiday

Post by Stunoodle » Sun Jun 22, 2014 10:17 pm

I've got a '62 Chris 18' Holiday that had a 283 in it. The beast finally kicked the bucket after over 50 years, and I replaced it with a 350 generating at least 100 more HP, so of course, I have to size a new prop. One of the critical questions is the gear ratio on the reverse gear. I can't for the life of me find the answer online, and I can't find any stamps, etc on the reverse gear that would help me. Does anyone know the gear ratio?

Thanks.

Stu

farupp
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Re: '62 Chris Craft 18' Holiday

Post by farupp » Mon Jun 23, 2014 10:44 am

My Sea Skiff with a 283 has a 1:1 gear ratio. I'm not sure if the gear ratio in reverse is any different. How fast do you want to go backward anyway?

I don't know if this helps but I feel the runabouts and utilities of the 50s and 60s had 1:1 transmissions.

There is an excellent article in the current Brass Bell about props.
Frank Rupp
1959 22-foot Sea Skiff Ranger
283 Flywheel Forward engine

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mfine
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Re: '62 Chris Craft 18' Holiday

Post by mfine » Mon Jun 23, 2014 11:06 am

I would highly doubt you had a reduction gear unless it was added later. What size prop did it have with the 283? That will be a good guide for what you will want.

BTW, chances are good the 283 prop will work OK, certainly for the engine breakin period and you can then see how it performs which is the best guide to selecting a new prop. I would guess if the old prop topped out around 4000 rpm with the 283, the 350 will spin it to 4500-5000 rpm depending on torque curve. After engine breakin at 3000-3500 rpm, see where the new engine tops out but I wouldn't run it above 5000 for very long if it can even get there. If it tops out at 4800 or less I might keep it. You may be sacrificing a bit of top end for acceleration but it is not a bad trade. If you want or need to lower top RPMs, knowing where you are will tell you what prop will get you where you want to go as far is increased pitch or diameter if there is space.

Check with the engine builder on the max cruise and max short duration RPM's he is comfortable with since it could be quite a bit different than 1960's builds. Most of the modern marine 5.7's are rated for peak HP around 4800-4900 rpm. Some builds may be ok to 5500. I think CC rated the 283 to 4000 rpm and the later 350's around 4400.

Stunoodle
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Re: '62 Chris Craft 18' Holiday

Post by Stunoodle » Mon Jun 23, 2014 2:25 pm

Thanks for responding so quickly to my post. The 283 had a 12", 13 pitch, 3 blade prop. The new engine completely overpowers it, I can only go half throttle before I hit 4500 rpm. My engine builder said 5000 rpm is the most I want to run the engine at. I'm trying to size the prop so I have lots of low end grunt, and WOT at about 4500-4800 rpm. I can guess what prop would work, but I need the gear ratio so I can get Acme Props to run an analysis on the boat.

There HAS to be a document somewhere that shows what my boat came stock with for a reverse gear.

Stu

jim g
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Re: '62 Chris Craft 18' Holiday

Post by jim g » Mon Jun 23, 2014 6:43 pm

Most of the boats in your size that came with a 283 came with a 12 X 15 inch prop. Your 12 X 13 inch was wrong for your 283. Most of the 283 to 350 conv. I've done have done fine with the 12 X 15 inch. For best performance you might want to try a 13 X 15. I use the original style T-36 design props.

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mfine
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Re: '62 Chris Craft 18' Holiday

Post by mfine » Mon Jun 23, 2014 7:06 pm

Reduction gear wasn't an option for the small boats like yours, only the big boys. The gear is 1:1 unless it has been changed since new. From what you are saying about the performance with the 12x13 it is still a 1:1 drive ratio.

The 18 Holiday came with a 185hp engine and a 12x15 (RH) or a 215 hp engine and a 12x17.

I would guess a 12x17 would be a good match for the 350 which will have a bit more than 215hp but also be able to spin a bit faster.

Stunoodle
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Re: '62 Chris Craft 18' Holiday

Post by Stunoodle » Mon Jun 23, 2014 7:32 pm

Mfine, you nailed it exactly. I called Acme Props in Michigan and spoke to an older guy who REALLY knows his stuff. He figured it out that it's a 1:1 gear just by my description of the performance, the year of the boat, the make, etc. And he recommended exactly what you said, a 12 X 17 prop, if it was a "traditional" prop. But Acme makes specialized props, and he thinks his 12.5 X 12 will be perfect for the boat. It's shaped differently and works a little different than traditional props. He said he's recommended that prop to many Chris Crafters with smaller boats, and they love it. Only issue is the Acme prop sticks out about 3/4" further than the traditional prop, and he was just a little concerned it would hit the rudder. I never really paid much attention to the distance between the traditional prop and rudder, but I've got to believe there will be enough clearance. I guess I'll find out. :)

Thanks again for all the help everyone.

Stu

Stunoodle
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Re: '62 Chris Craft 18' Holiday

Post by Stunoodle » Sun Jul 06, 2014 10:49 pm

Finally got the new prop from Acme Props, holy cow, what an immense difference! We went out wake boarding over the July 4th holiday weekend, and had 8 people on the boat, and no issue at all pulling up a rider. In the past, we couldn't have more than 4 people, and it took quite awhile to get the rider up. Now it happens virtually instantaneously.

I ended up getting the Acme 1210, which is a 12.50 diameter 12.000 pitch 0.080 cup 3 blade prop. I had a long conversation with Jim Thelen at Acme, (extremely knowledgable and helpful guy) and he was pretty certain this prop would do the trick. Man does it ever.

Of course, there's always another problem that surfaces when you repower an old boat, and I was anticipating this, but now I need to figure out a solution.

So basically, back when the old tired 283 was in the boat, and the standard prop was installed, when the engine was cold (or more specifically when the engine oil was cold), it you went WOT, the reverse gear would "slip", or essentially it would disengage and the motor would spin free. You would of course have to back off quickly or risk blowing the engine. As soon as the oil warmed up, it wasn't a problem anymore.

Now, with the engine so much stronger, and the Acme prop being able to push so much more water, you have to very carefully accelerate up, or it will break loose like before. Happens all the time, either cold or hot oil. There's just too much power and resistance from the prop. (this was also happening with the old, standard prop but not as much as now)

I'm wondering if there's some way to adjust the reverse gear, so it's "tighter" and won't spin out? The reverse gear is probably the only thing on my CC that I don't mess with, and barely understand, so I'm gonna need an education.

Many thanks.

Stu

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mfine
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Re: '62 Chris Craft 18' Holiday

Post by mfine » Mon Jul 07, 2014 6:13 am

You should be able to search the forum and find plenty of threads on adjusting the reverse gear/transmission.

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