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Reversion.... am I ok?

Old 02-12-2014, 10:58 AM
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Originally Posted by 4bus
I know you are on a budget, but you should have used the resources here before you spent money

Some things to keep in mind with your set up, don't push it too hard. The fact that you have a heavy load "wet" boat makes it even more crucial. I would lock the timing and be conservative on your AFR on the rich side and prop for 4800-4900 rpm. Those pistons will not tolerate much, if any detonation. And as stated above you will be limited on total rpm, but over propping and loading it down will increase your chances of detonation. You are running a fine line squeezing reliable HP out of that set up. Not saying it can't or hasn't been done, however it is not the ideal setup for those that have already learning the hard way.
Just noticed the part about the non-forged pistons. Forged would be money well spent in this area. Definitely keep the CR below 9:1 with these, and I would stay conservative on the timing and stick with at least 91 octane. Big heavy boat like this would have been a great candidate for a stroker kit. They are available with forged pistons for less than $1500.


Originally Posted by 4bus
On a side note there is a guy on my lake with a 330HP with a 177 blower on it, stock internals. Has been running 4.5 of boost for years with no issues, 10 mph gain. So....who knows
Some folks just seem to live a charmed life - at least with mechanical things. I'm not one of them!
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Old 02-12-2014, 05:40 PM
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Seems like u guys are worried about the pistons. I would worry more about the rods than anything. I know boats and cars don't see the same harsh conditions but I have saw lots of nitrous BBC with hyper pistons. I have good luck with them. I would not worrie about any of his setup. Unless all he can find is 87 octane. Then maybe some pinging but a couple bottles of boost will help that. I have never bought fuel on a lake so I don't know what octane marinas sell?? I have 11.2 to one in my boat but I use 93. 87 is for lawn mowers
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Old 02-12-2014, 06:55 PM
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Teague sells takeout 7/16 Dimple rods cheap. You can get a speedpro forged piston real reasonably priced.
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Old 02-13-2014, 10:44 PM
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I had planned on running at least 91 octane at all times, but probably 93 more than anything. I trailor it everywhere and always fill up on land, and if I do need to fuel up on the water, It's LOTO and every octane is available. I do realize that forged pistons and rods are prefered, and I do know that the 3/8 rods are the weak link.... however, saying that, I also know that 91-93 octane on 9:1 compression hyper pistons at a 500hp level is safe enough, and the same can be said with 3/8 rods If they have ARP bolts and don't go much past 5000rpms. This is my first marine engine build, but have been building engines for 15 years, so I'm fairly confident I should be ok if I'm not a douche on the throttles, lol. I'm saving my no-holds-barres engine build for when I have a faster hull performance V boat, but just wanna be able to haul my coolers to the sandbars and party cove a little faster the nest 2 years lol I REALLY appreciate you guys' input tho, definitely gives me something to think about.
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Old 02-14-2014, 09:04 AM
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Originally Posted by gmgearhead454
I had planned on running at least 91 octane at all times, but probably 93 more than anything. I trailor it everywhere and always fill up on land, and if I do need to fuel up on the water, It's LOTO and every octane is available. I do realize that forged pistons and rods are prefered, and I do know that the 3/8 rods are the weak link.... however, saying that, I also know that 91-93 octane on 9:1 compression hyper pistons at a 500hp level is safe enough, and the same can be said with 3/8 rods If they have ARP bolts and don't go much past 5000rpms. This is my first marine engine build, but have been building engines for 15 years, so I'm fairly confident I should be ok if I'm not a douche on the throttles, lol. I'm saving my no-holds-barres engine build for when I have a faster hull performance V boat, but just wanna be able to haul my coolers to the sandbars and party cove a little faster the nest 2 years lol I REALLY appreciate you guys' input tho, definitely gives me something to think about.
Good luck with everything. Saying 500hp with cast pistons is safe, maybe....but for how long? There isn't a manufacture out there making the HP you seek in a marine engine with a warranty. The industry has deemed it is not safe. You have no window for error with that set up. Water in fuel, heavy load, high heat will end your hard work quickly.

You still have time to return those pistons, beef up those rods, and go with forged for piece of mind. I have seen rectangular port heads loaded for $500 bucks. You would have the making of a proven merc 500 hp engine sans the crank.
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