repower 283/HF7 with 350 questions

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repower 283/HF7 with 350 questions

Postby Cary » Sun Apr 07, 2013 11:04 am

Good Morning.

I'm new to the Club and have been reviewing previous posts for answers to my these questions, but have not found all of them.

I have a 20' 1962 Holiday that originally was fitted with the 431. I purchased the boat without an engine/transmission and was able to acquire a 283 flywheel forward engine with a model HF7DR Paragon hydraulic gear. The engine is worn out but all of the Chris Craft marine hardware is present.

My plan is to replace the 283 with a re-manufactured marine 350 long block and use the HF7 gear.

Question #1:
Because this boat originally had the 431ci/275HP engine, the upgrade to a roughly 250hp SBC should not be too much power for the boat. Will the 185hp 283 components (intake manifold, carburetor, exhaust manifolds, water pump, etc.) be able to support the 250hp from the 350 new engine?

Question #2:
It appears from other forum posts that if I source a 1967-79 350 marine long block, all of the 283 CC specific components will fit up properly. Am I missing anything with this idea?

Question #3:
On-line information that I have seen suggests that the HF7 is suited for the 185hp 283, but that is near the maximum rated hp. Does anyone have experience with mating a 250hp engine to an HF7 gear? What might be the failure mode if I do run this gear with this higher horsepower engine? If an upgrade is needed, please provide gear specifics.

I've got a long way to go to get this boat back on the water, but want to start collecting the proper parts and knowledge now.

Thanks in advance for any and all replies.
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Postby Don Ayers » Sun Apr 07, 2013 11:38 am

What you are wanting to do has been done many many times prior.

No real issue with an HF7 to my knowledge. Done it myself and it's a strong gear.

There are differences in the block of the original 283 and a 350 core most notably the crank case breather. You will have to vent the block through the value covers. You will also have to think about carb/cam/compression selection as well. Also keep in mind that the flywheel forward CC is in the boat backwards in relation to the car application. So things need to be set up to turn the right direction.

PS. You can certainly get more than 250 HP out of the 350 SBC. I would expect a base of at least 270 but not that hard to get 300 HP.

Other things are that your engine box will be way bigger than you need so you might consider making the smaller one.

My first question is why not go back the the big block Lincoln? Keeps boat more original, better value, Hell of a torque monster engine...

I have owned three of these boats and rode in other big block versions and can tell you they are a much different experience.

Also that boat was delivered with the Chrysler 413 which is a Hell of a motor. I'd also consider putting in one of those and keep the boat a big block.

PS. Big block boat also had the exhaust in out locations.

You see there are a lot of things you need to consider that are going to not only take some cool out of the boat but IMHO greatly de-value it in the future.

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Postby jfrprops » Sun Apr 07, 2013 7:07 pm

Every Word in Don's post is RIGHT ON.

If cost and utter reliability are factors...I might also op for the new 350SBC.
And for sure you can get equal HP out of one.

But for orig. and sexy.....big block for sure.

No issue with the HF7 hydralic unit....will work fine.

Sounds like you have no reduction going on though?

Right?

Would not need any for a boat that size.

Neat project....get it done and go boating!

John in Va.
1980 Fairchild Scout 30
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1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)
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Postby drrot » Mon Apr 08, 2013 8:15 am

I have never put a 350 in the place of a 283 with a hydraulic gear but on the manual gear there is one issue. You need to watch is oil pan clearance. The counterweights on the 350 are farther out due to the longer stroke. When you have the long block upside down install 4 studs in each corner of the block where it would bolt on. Set the oil pan on the studs and rotate the crankshaft both ways. You can usually see where a counterweight will lift the oil pan. Take a grinder and remove material till the crankshaft rotates all the way around without hitting. Go an extra bit to accommodate any expansion when hot.
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Re: repower 283/HF7 with 350 questions

Postby Cary » Mon Apr 08, 2013 7:46 pm

Gentlemen, thank you for your replies.

I will try to answer your questions now.

My plan is use the SBC due to its availability, price and the fact that I have the gear for it now. Here in SW Missouri I have not seen a marine version of a 431 or 413 in person. I understand the value of keeping it original and would not make any changes to the hull that would diminish its value. If I were to come across a 431 that I could pick up reasonably, I would seriously consider a purchase. I understand that I will have to determine the engine rotation before ordering a long block. I'm glad to hear that the HF7 will handle up to 300HP.

The Paragon HF7 that I have is a 1:1 drive. I was concerned about the HP that the 283 hardware can handle and am pleased to hear that 260-300 HP is OK for the drive

The tip about crankshaft clearance is greatly appreciated.

I've got a few years to get the hull repaired and get the gear re-conditioned, but wanted to get some advice before I travel further down the road.

Thanks for your help.
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Re: repower 283/HF7 with 350 questions

Postby rbrinks » Wed Feb 15, 2017 2:05 pm

did you ever finish the boat. I have a 20' Holiday without a engine also. originally it had a 431. i'm thinking about doing a 350 conversion to my project too. would like to know how yours turned out.
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