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Cracked 4.3 - upgrade to 5.7 or vortec?

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Cracked 4.3 - upgrade to 5.7 or vortec?

Old 06-13-2019, 04:01 PM
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Default Cracked 4.3 - upgrade to 5.7 or vortec?

Considering buying a kinda rare boat for cheap. 1989, hardin marine/tahiti/Caribbean "invader" 17' or 18', has an alpha 1 and I'm told a 4.3 v6. Body/interior seem to be in excellent shape. I am told it has cracked exhaust manifold(s) and it's fair to assume that's from poor winterizing and the whole engine might be junk, so my offer would reflect that. Probably $1k. And while replacing the engine, if it fits, I'd rather replace it with a v8. What I like most about it is that it has a pretty unique and uncommon look to it, small boat with a closed bow and sun deck on the back. And I also just love small vehicles with large engines.

So this is what I'm considering. Either I could replace it with a strictly period correct super basic rebuilt 5.7 SBC, or I love the idea of swapping a gen III or newer vortec style engine like a 5.3 or 6.0. I'm really good at turning a wrench, electrical, and mild fabrication doesn't scare me. I know modern fuel injection a lot better than carbs. In this situation, is it worth the $ and hassle to even consider going vortec? Or should I just keep it simple and go 5.7? Have you guys seen any examples of a vortec swap and what's entailed? I've also considered doing a basic 5.7 swap and a self learning throttle body injection setup with an O2 sensor.

Edit: found the pictures!









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Old 06-13-2019, 04:28 PM
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Originally Posted by Mrbighughjass View Post
Either I could replace it with a strictly period correct super basic rebuilt 5.7 SBC, or I love the idea of swapping a gen III or newer vortec style engine like a 5.3 or 6.0.
Either way you go, this has yes written all over it, love it. Would also love to see some pics!
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Old 06-13-2019, 04:40 PM
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Done!
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Old 06-13-2019, 05:57 PM
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Pretty sure when you move up substantially in HP your going to need a outdrive/ prop to match it . Gear ratio may be different . Also wiring harness may be different or require some tweaking to have your gauges work.
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Old 06-13-2019, 06:03 PM
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Alphas are not very strong, and they are restrictive for big engine exhaust. 350/2bblwould be plenty.
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Old 06-14-2019, 01:34 AM
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looks like a cool boat, check how much room there is in front of the engine with the V6 installed, the 5.7s are about 3.5" longer. I would stick with a simple carbed engine in a repower.
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Old 06-14-2019, 05:23 AM
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Is putting the TBI on the 5.7 an option. With the 4.3 you should already have the TBI just change out the injectors and re chip the ecm.
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Old 06-14-2019, 05:34 AM
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Big ass headaches are in your future if you buy that mess.
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Old 06-14-2019, 05:52 AM
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Yeahhhh, sorry to harsh the mellow but....

KISS.

Put a GEN III 4.3 in it. Outdrive, output and legal will matchup. That 4-blade prop indicates it is already stern-heavy/slow hole shot so not a good design imo if that's how it rolled out. Without a special re-titling for the larger engine the 5.7 will likely void its max HP rating making you liable for all sorts of penalties should something 'not good' happen involving other persons or property. Also, lots of hulls do strange things when over-powered like wobble, walk, jump, spin and flip. If not it'll likely just come apart before your eyes (seen that) with the finale being the engine goes to the bottom and you get to swim to shore after you find a lifejacket -or not.

Last edited by Scupperz; 06-14-2019 at 06:11 AM.
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Old 06-14-2019, 06:18 AM
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Carb V8 that girl! V6 is for p*****! Make it a rat rod for the water!
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Old 06-14-2019, 06:35 AM
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I'd rather have a 4.3 Vortec with a well set up 4bbl carb, if you go V8 keep in mind that with a 5.7 you are at the limit for an Alpha drive and the gear ratio is not right for the V8 (will limit your top speed but out of the hole performance will be better). If you can get information on the boat and find out what engines were options, you can find out of the V8 was offered in a boat that size. Also and this is just my preference I would not install a new inboard engine in any boat without closed cooling, you usually need more room in front of the engine for that to fit. So measure how much room you have and also measure how much room there is on the engine mount pads, you need at least 3.5" forward for the V8 mounts to fit....
Anything beyond a 5.7 4bbl and the Alpha drive will be beyond its max. Then you re into a complete repower to a Bravo series replacing the drive and transom mount. A lot more $$ and weight. In my opinion not needed. Stay away from complex EFI systems that use marine manufacturer specific parts. They have a lousy habit of making parts NLA after about 10 years and then you are left with a system that can't be fixed. You can always get a new Holley or Edelbrock 4bbl and aftermarket electric low pressure fuel pump. Ya just gotta learn carbs.
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Old 06-14-2019, 08:35 AM
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Originally Posted by LouC View Post
I'd rather have a 4.3 Vortec with a well set up 4bbl carb, if you go V8 keep in mind that with a 5.7 you are at the limit for an Alpha drive and the gear ratio is not right for the V8 (will limit your top speed but out of the hole performance will be better). If you can get information on the boat and find out what engines were options, you can find out of the V8 was offered in a boat that size. Also and this is just my preference I would not install a new inboard engine in any boat without closed cooling, you usually need more room in front of the engine for that to fit. So measure how much room you have and also measure how much room there is on the engine mount pads, you need at least 3.5" forward for the V8 mounts to fit....
Anything beyond a 5.7 4bbl and the Alpha drive will be beyond its max. Then you re into a complete repower to a Bravo series replacing the drive and transom mount. A lot more $$ and weight. In my opinion not needed. Stay away from complex EFI systems that use marine manufacturer specific parts. They have a lousy habit of making parts NLA after about 10 years and then you are left with a system that can't be fixed. You can always get a new Holley or Edelbrock 4bbl and aftermarket electric low pressure fuel pump. Ya just gotta learn carbs.
actually a 4.3 vortec was my first idea, and itís definitely on the table, i also do really like the idea of the closed loop cooling. Online it looks like a v8 was an option when you look up values so it might already be setup nice for a v8.

And thanks for the heads up on the efi kits. I know the basics of how carbs work and iím not afraid of learning more, itís just from a maintenance and tuning standpoint, fuel injection and distributor-less ignitions are just so vastly superior. Set it and forget it.

Iíve heard that alpha 1ís can be iffy for large heavy boats with a 5.7, so i figure a 17 or 18í boat with a 4.8 or 5.3 should be pretty safe. Chevy put those motors in absolutely everything so they are super plentiful and cheap. Itís also been my understanding that torque is really what breaks things not hp. Like a 250 horse big block that makes monster torque off idle might be more prone to breaking parts than a 400 hp 5.3 that has to rev really high to make that 400hp.
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Old 06-14-2019, 08:37 AM
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Originally Posted by Pursuit1 View Post
Is putting the TBI on the 5.7 an option. With the 4.3 you should already have the TBI just change out the injectors and re chip the ecm.
yes, tbi is definitely something iím very interested in.
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Old 06-14-2019, 08:52 AM
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Originally Posted by Scupperz View Post
Yeahhhh, sorry to harsh the mellow but....

KISS.

Put a GEN III 4.3 in it. Outdrive, output and legal will matchup. That 4-blade prop indicates it is already stern-heavy/slow hole shot so not a good design imo if that's how it rolled out.
Tell me more about this prop/weight issue. I donít know much about prop selection. If it is stern heavy, an all aluminum 4.3 with a closed water cooling would probably lighten it up some.
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Old 06-14-2019, 09:16 AM
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after all the talk about engines etc have you checked the structure for rot? Boats of that vintage are typically wood cored everywhere and it can be an overwhelming job to fix.
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Old 06-14-2019, 10:04 AM
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Originally Posted by LouC View Post
after all the talk about engines etc have you checked the structure for rot? Boats of that vintage are typically wood cored everywhere and it can be an overwhelming job to fix.
Not yet, I will when i check it out in person. itís a bit of a long drive. But iíve known the owner a very long time and know itís been stored indoors in a huge shop for at least the last 15 or 20 years. Iím not sure if he bought it new. If it has any rot iím not going to touch the thing. The whole idea of getting it hinges 100% on the body and interior being in absolutely excellent shape for their age.
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Old 06-16-2019, 08:44 PM
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Update, after lots of research and due to a lot of the things you guys brought up, I think if I do get the boat I'll just be doing a "keep it simple stupid" situation. Either replace it with a standard 4.3, or a standard 5.7 if it fits. Maybe throttle body injection and/or closed loop cooling. The question is now, where's the best place to get a good quality long block and exhaust manifolds for the price? I don't care about higher than stock hp numbers really, more about it being good quality parts, machining, and assembly, and not just some shit rebuilder who will sell it at a low price.
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