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Engine Technical Discussion This is our non outboard engine related technical discussion forum. If your boat is powered by a Inboard/Outboard, Jet drive, V-drive, or even something else, then this is the forum for you! Topics include engine repair and maintenance, modifications, drives and gearcases, electrical and electronics, etc. For technical assistance related to outboards, please use our outboard tech forum.

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Old 02-06-2019, 07:51 AM   #1
Cdowjr
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Default Twin 30 foot checkmate with 632 ci engines

I’m repowering a 1988 30 foot checkmate twin I/o
TRS drives.
Why don’t I find any of these 30 foot boats out there? Did they make.
Any reason why the revolution 4 props won’t work?
Do you think it will run nicely with twin 850 hp engines? What props
would you recommend?
Does anyone in the north east have one of these? I’m in maine.
Shortblocks I bought are from blueprint engines. 4.75 inch stroke. That’s making it hard to find an oil pan. Why doesn’t someone make a one inch spacer so a stock oil pan will work?
If I set it up as closed loop cooling how difficult is it to get a system that will handle 850 hp? Will mercruiser stuff from day a 502 work?
Any advice would be appreciated
Cliff
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Old 02-06-2019, 09:23 AM   #2
Gimme Fuel
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You will be putting some serious HP in front of those TRS drives. I think you will find that the factory transmissions will not like that much HP. Drives are reasonably stout but you might want to keep spares with that much power they could break at will. TRS are not known for handling big power and have a relatively poor shaped lower gearcase for high speeds. Moderately more reliable than a Bravo...but not much.

You will also want full hydraulic steering with that much HP and speed potential if boat is not already equipped. Major safety and handling concerns without it considering your plans.

I will say this, the factory GM 8 quart pans have terrible windage control for a 4.25" stroke/higher than stock RPM let alone your 4.75" stroke motor. You will thank yourself later to buy new oil pans with good windage trays. Kevco makes nice reasonably priced pans.

Your stock 502 heat exchangers and oil coolers will be woefully inadequate for that much horsepower. As will the entire stock oiling system, fittings, and small lines. This type of ancillary stuff is where big HP builds gulp a ton of unexpected budget. You are probably facing $2k+ per engine for these systems alone to handle that HP with closed cooling.

If you get it all to work, the boat should absolutely fly.

I absolutely hated the way a Rev4 prop handled on my 700HP powered 253 checkmate. Too much stern lift made the bow steer terrible. Also, they only go up to 25" pitch which depending on what rpm your camshafts make power, will likely be too small. I loved the handling of Hydromotive QIV props on mine and the Merc Bravo I props work well too.
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Old 02-06-2019, 12:48 PM   #3
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We're going to need some pics of this bad boy!👍

Good luck-
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Old 02-07-2019, 07:02 AM   #4
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Pretty much everything Gimme Fuel said is spot on. No way will anything off of any stock 502 work for your setup except for the stock accessories maybe, but probably not if you go with closed cooling. I run a KEVCO oil pan on my engine and I'm very happy with it. Price was reasonable as well.

What cam and heads are you running on the engines? I have a buddy that is using a Blueprint 632 in his HTM. They are great engines.
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