outboard to inboard conversion

taqwache · #1 06-24-2007, 11:47 PM

ok here is a good one. i got a 78 V20 steplift that has been in the family since 1979. it came from the factory with twin 75hp mercs. after 10 years or so of saltwater use, those went bad and my dad repowered with a single 175 mariner. now after another 10 years or so of saltwater use, it has also gone bad along with the transom. since then the boat has been sitting for 5 plus years in his back yard. now me and my dad plan on restoring it. i found this site and noticed that these boats also came with inboard/outboards which is what i want to use. since the whole transom needs to be replaced anyways, how hard would it be to just mod it for and inboard/outboard? i was planing on useing a modified 400hp 6.0L gen3 chevy with a mercrusier alpha one. i know it will be difficult but that does not matter. i am very mechanicly inclined but i dont have to much boat experience. although i can learn very quickly. i can build a motor for almost free but i will have to buy all the other marine parts. what do yall think? what else is different from the two styles of boats (OB and IB/OB) that will be a challange?

frayed_knot · #2 06-24-2007, 11:52 PM

You won't get much support with that mod I'm afraid. Most everybody does the opposite. I'm sure it's do-able though, but will require a "boat load" ( ;D) of structural mods to be able to bolt an engine into the hull. Your choice of engine and drive is curious to me. Why go with that engine? An Alpha 1 of any generation is not a good choice for anything above 300 hp. You would be much better off with a Bravo drive. I would spend the $$ on a good OB after restoring the transom.

frayed_knot · #3 06-24-2007, 11:52 PM

You won't get much support with that mod I'm afraid. Most everybody does the opposite. I'm sure it's do-able though, but will require a "boat load" ( ;D) of structural mods to be able to bolt an engine into the hull. Your choice of engine and drive is curious to me. Why go with that engine? An Alpha 1 of any generation is not a good choice for anything above 300 hp. You would be much better off with a Bravo drive. I would spend the $$ on a good OB after restoring the transom.

spareparts · #4 06-25-2007, 12:29 AM

I'd have to agree with frayed and I'm a Mercruser Tech by trade. Thats way too much hp for this hull, it would go to waste. The bravo would be a better choice for that engine as well, you could git an Alpha to hold it if you wern't dogging it too hard. Best solution if you want to have an I/O. Trade your boat to some one with an I/o boat that wants to convert to an outboard. Espcially in salt water, your just asking for more work. If you really want an I/O, try a Volvo 5.7 320 HP with the XDP composite drive. Thats a slick package and salt won't touch it( I service a pair XDP's behind twin 8.1's in a 34 Cruiser). If you allready have the engine, try finding a used 22 Velocity(Regal sold them for a while), thats a boat that will put that motor to good use

spareparts · #5 06-25-2007, 12:29 AM

I'd have to agree with frayed and I'm a Mercruser Tech by trade. Thats way too much hp for this hull, it would go to waste. The bravo would be a better choice for that engine as well, you could git an Alpha to hold it if you wern't dogging it too hard. Best solution if you want to have an I/O. Trade your boat to some one with an I/o boat that wants to convert to an outboard. Espcially in salt water, your just asking for more work. If you really want an I/O, try a Volvo 5.7 320 HP with the XDP composite drive. Thats a slick package and salt won't touch it( I service a pair XDP's behind twin 8.1's in a 34 Cruiser). If you allready have the engine, try finding a used 22 Velocity(Regal sold them for a while), thats a boat that will put that motor to good use

willy · #6 06-25-2007, 12:54 PM

If you are going to do the transom restore, I would suggest you close it in completely and add a full bracket to the back and add a single 150 etec or similar motor. Nothing bigger and you will have a mid forties performer that will be less maintenance intensive and generally more reliable across the board. Actually if you add a 115 - 150 to a bracket on the back of that boat you will have the best performance package you can have, it will be very quiet behind that full transom and you will increase the sea worthiness of your V at the same time. JMHO

willy · #7 06-25-2007, 12:54 PM

If you are going to do the transom restore, I would suggest you close it in completely and add a full bracket to the back and add a single 150 etec or similar motor. Nothing bigger and you will have a mid forties performer that will be less maintenance intensive and generally more reliable across the board. Actually if you add a 115 - 150 to a bracket on the back of that boat you will have the best performance package you can have, it will be very quiet behind that full transom and you will increase the sea worthiness of your V at the same time. JMHO

msbhammer · #8 06-25-2007, 01:39 PM

Go Bracket son. ;D ;) and of course...post Pics. ;)

msbhammer · #9 06-25-2007, 01:39 PM

Go Bracket son. ;D ;) and of course...post Pics. ;)

reelapeelin · #10 06-25-2007, 03:14 PM

OK taq ... ya stated what ya wanna do and everybody's tryin' to talk ya outta it ... fact is, you can do most anything your wallet and skills can cover w/these hulls ... if I were doin' what yer talkin' about, I'd take the floor deck up and beef-up the stringers to handle the weight/power of the motor you want ...while yer that far into it, take the cap off and replace the notched transom w/a full one ... keep weight in mind, but put it all back STRONG ... post some pix here thru the modification ... I'd like to see it happen ... oh yeah...I think the '78 had a small gas tank (42?) ... be a good idea to add more fuel capacity while yer at it ;) ...