21' Sea Ray engine swap

[admiral52]

I Bought a 86 Sea Ray 21 foot to restore. The engine (5.7l) has had it. I'd like some input on whether there is a better choice to put in it.

Would it be worth putting a lighter engine in it with similar HP? (this boat will never see salt water)
Does a higher HP engine have better fuel economy if you stay off the Throttle?
Is it POSSIBLE to use a vehicle fuel injection system on a boat? Does anyone make an aftermarket fuel injection system that's a better choice?
Any thoughts on cooling? I have a heat exchanger I can use. Is a closed system better if I use aluminum heads?

Anyone have some interesting ideas on engine choices?

Bare in mind that fabricating my own parts isn't an issue, neither is programming an ECU. I don't mind tons of work (keeps me busy).

Please make the info you give helpful. I don't need "the easiest thing would be to use the same engine it came with" or "ford is better, no chevy is, no dodge"

 

[slothman]

Re: 21' Sea Ray engine swap

I Bought a 86 Sea Ray 21 foot to restore. The engine (5.7l) has had it. I'd like some input on whether there is a better choice to put in it.

It depends on how much money you want to spend, and how much power you want.

Would it be worth putting a lighter engine in it with similar HP? (this boat will never see salt water)
Does a higher HP engine have better fuel economy if you stay off the Throttle?

Usually more HP means you have a bigger motor. Which usually means worse MPG.

Is it POSSIBLE to use a vehicle fuel injection system on a boat? Does anyone make an aftermarket fuel injection system that's a better choice?

If you want FI just buy a marine motor that has FI.

Any thoughts on cooling? I have a heat exchanger I can use. Is a closed system better if I use aluminum heads?

closed cooling systems are more headache, trust me.

Anyone have some interesting ideas on engine choices?

IMO the 350 is a very stout, reliable engine. If you are looking for more power then get a 454. If you want slightly better MPG stay with the 350. I think the cheapest/best option for you is to just rebuild the motor that is currently in the boat.

Bare in mind that fabricating my own parts isn't an issue, neither is programming an ECU. I don't mind tons of work (keeps me busy).

Please make the info you give helpful. I don't need "the easiest thing would be to use the same engine it came with" or "ford is better, no chevy is, no dodge"

 

[Howard Sterndrive]

Re: 21' Sea Ray engine swap

I don't need "the easiest thing would be to use the same engine it came with"

yes you do

what do you need? A complete dressed engine with electrical and exhaust manifolds? Or just a long block?

 

[hivoltg]

Re: 21' Sea Ray engine swap

I would stay with the 350 motor if it was me. Add all the internal parts you want to get the horse power you want out of it. If you really want to get a tpi wire harness/intake and make it work...im sure you could.

Putting whatever motor you want in it is a choice, but keep this in mind....everything on the boat is affected by the change. The way the exhaust manifolds/risers routes is a big one that gets expensive. The drive alignment, shift and throttle linkages, outdrive gear ratios, and so on.

Expect the parts to be triple the cost of a car part because it says marine on it. It makes no sense but welcome to the game. : )

Im sure you have done the trial and error with upgrading cars like I have, new fuel maps, and all that fun stuff, but in a boat its different. You and your family are out on the water when you figure out that didn't work. No amount of ear muff trial time can indicate the "we are now taking on water" moments when an exhaust bellow or other part isn't positioned right at 4500rpm under load.

Also keep in mind that the alpha 1 outdrives only like about 300hp max before they start to break...

 

[admiral52]

Re: 21' Sea Ray engine swap

Should have been more clear. I know the easiest thing would be to rebuild the stock engine. But this will most likely be a mod, not just a restore. Cost is an issue to an extent, but I'd like to do something out of the ordinary.

 

[slothman]

Re: 21' Sea Ray engine swap

Should have been more clear. I know the easiest thing would be to rebuild the stock engine. But this will most likely be a mod, not just a restore. Cost is an issue to an extent, but I'd like to do something out of the ordinary.

Then swap to a 454. won't be cheap though. I'm not sure why you don't like the 350. Plenty of power, very reliable.

If you wan't "custom" you could slap a supercharger on the 350, but the outdrive can only handle so much power...

Plus this is a 86 searay.....why in the hell do you want to dump tons of money into it ???? You're going to lose all the money you spend on it. In the end, it will still be a 86 searay lol .....not a custom drag boat ....

 

[thumpar]

Re: 21' Sea Ray engine swap

If you do too much you will need a new drive to handle the power and get the ratio correct.

 

[admiral52]

Re: 21' Sea Ray engine swap

Why would I want to dump money into it? Ummm, the same reason anyone on this forum does. Anyone here fixing up a boat to make a profit? Boats are money pits, no doubt. I bought the boat for $400 to have a project. A hobby. Not just to hit the lake with. The boat books at 4200, subtract the 400 I paid, that leaves 3800 before I'm upside down on it..

 

[matt167]

Re: 21' Sea Ray engine swap

Boats usually don't make a profit. If the stringers, transom and deck are rotten, ( usually are on $400 boats ) than that will take up $2-3k and you will end up putting a used truck 305/350 in and swapping over the marine parts it so you don't end up 'upside down'.. Hopefully the interior would clean up at that point

 

[slothman]

Re: 21' Sea Ray engine swap

Why would I want to dump money into it? Ummm, the same reason anyone on this forum does. Anyone here fixing up a boat to make a profit? Boats are money pits, no doubt. I bought the boat for $400 to have a project. A hobby. Not just to hit the lake with. The boat books at 4200, subtract the 400 I paid, that leaves 3800 before I'm upside down on it..

well if you're planning to flip it, the SMARTEST thing to do would be an engine rebuild on the 350 motor. That would be the least expensive option.

If you want a TON of work, put in a bigger motor.

I'm guessing if you bought the boat for $400 it needs A LOT of work

 

[stonyloam]

Re: 21' Sea Ray engine swap

I wouldn't worry so much about the engine yet. The things you need to worry about are the condition of the hull, and the outdrive, especially the outdrive, that can get you upside down in a hurry.

 

[admiral52]

Re: 21' Sea Ray engine swap

The deck, stringers and transom are in great shape;-) it needs upholstery though.. And I'm not looking to flip it. I'm sure I will use it when complete for sure;-) my purpose is for a project. Something to put a few years into before it's done. My last one was a fox body mustang with a 5.8 motor that took 2 years. Drove it for 2 years then sold it. Didn't profit but it was a lot of fun to build. Thought this time I'd try a boat. I want to keep it under 4200 just to limit myself. Not to profit

 

[HT32BSX115]

Re: 21' Sea Ray engine swap

I Bought a 86 Sea Ray 21 foot to restore. The engine (5.7l) has had it. I'd like some input on whether there is a better choice to put in it.

Would it be worth putting a lighter engine in it with similar HP? (this boat will never see salt water)
Does a higher HP engine have better fuel economy if you stay off the Throttle?
Is it POSSIBLE to use a vehicle fuel injection system on a boat? Does anyone make an aftermarket fuel injection system that's a better choice?
Any thoughts on cooling? I have a heat exchanger I can use. Is a closed system better if I use aluminum heads?

Anyone have some interesting ideas on engine choices?

Bare in mind that fabricating my own parts isn't an issue, neither is programming an ECU. I don't mind tons of work (keeps me busy).

Please make the info you give helpful. I don't need "the easiest thing would be to use the same engine it came with" or "ford is better, no chevy is, no dodge"

Howdy,


Welcome aboard!

You're not going get any "Ford vs Chevy/dodge" arguments here.......The only marine engines manufactured now are GM

You can easily rebuild your 5.7L engine and the most bang for the buck would probably be another 5.7L carbureted engine. EFI will be prohibitively expensive since you need a marine system. If you want to to do that "Knock yourself out"!!

Automotive EFI is MUCH harder but doable.......and you could run afoul of USCG regulations (you'll get all sorts of arguments here) ..........my only concern is the liability of using obviously NON-USCG approved stuff then having it blow up and kill the neighbor kid on an outing. When the dead kids family lawyer finds out that you used NON-USCG "stuff" they will use the info against you in a civil case etc.......

There's nothing wrong with closed cooling. It's a bit more complicated but not impossible. I bought a complete San Juan Engr system for my 454 and it works flawlessly! Your engine will ALWAYS run better if allowed to operate at a higher stable temp (that closed cooling allows) and you'll never have to worry about a [freeze] cracked block!!

You can also then go to aluminum heads, manifolds and risers (risers are always raw water cooled btw)

The reduction in weight is significant. The COST is NOT. And I'm not sure it's worth it........BUT my dream engine for my 1987 Fourwinns Liberator would be an ALL aluminum EFI small-block, with aluminum manifolds, risers, heads, etc.

You can also get away with slightly more compression (better detonation suppression) because of the better heat transfer but again, MORE money is required.$$$


I am not sure that an 86 model boat is worth an engine that will cost FAR more than the boat is worth when it's all done........

It also depends on how much "bang" you want. If you get too much, you'll need to either rebuild your drive or replace it with a Bravo because an Alpha is good for approx 300hp. +/- If you're gentle, the Alphas will work.......But if you're building all that power, you don't want to be gentle do you ?


You fuel consumption will be directly related to how you handle the throttle! (However, TRUST ME!..... if you got it, you'll use it!!)


Cheers,


Rick

 

[admiral52]

Re: 21' Sea Ray engine swap

Thanks rick!! That's just the answer I was looking for! ;-)

 

[81 Checkmate]

Re: 21' Sea Ray engine swap

My humble opinion…….Never seen a $400 dollar boat that didn’t have a soft deck.
If it’s soft anywhere it is most likely to have some stringer rot.

As far as the power plant…cu do’s to someone with a imagination to want something different…. Motor wise/off the wall/different

But your gona flip the boat in a few years………If I were looking for a boat in your price range…I wouldn’t touch it with a 10ft pole, only if it were done very professionally…… and I could get parts for it! Ah…still wouldn’t buy it!

Spend the $3800 on a resto project with the same power plant/ redo the stringers/deck……..and enjoy the boat a few years/ flip it and get a different one. Say maybe a Jet Boat with a Big Block and Zommies out the back!

Good Luck!

 

[stonyloam]

Re: 21' Sea Ray engine swap

I agree with HT32, if you are looking for a project, and your engine is rebuildable, rebuild it! Just remember you are building a truck engine, you want torque. Have fun.

 

[andrew91]

Re: 21' Sea Ray engine swap

Wow guys aside from a couple talk about shooting a guy down i'd replace my 350 with a ford big block or chevy 454 yes you can buy ford marine engines but this guy stated he dont like his 350 he dont want to rebuild it i actually like mine and im a ford boy but man if I were i'd choose a bigger motor and toy with it just dont go far from the ramp if you have to paddle back youll stay closer next time lol I have looked into doing a 454 swap and these guys are right if its an alpha one which mine is you will want to upgrade id just rebuild the alpha drive (simpler than bravo IMO) they can be built to take a beating and just getting the kinks worked out will drive you nuts throttle linkages etc. but im with you im a fuel injection boy and please do let us know what you decide to do the easiest motor to get ahold of if you go to big block is the 454 which you can easily get 400 horse to 500 horse out of without going nuts 400 is more realistic I would stick with external cooling its simpler but thats me my uncle has plugged to many heads up and now has a closed system minus the risers Boats are money pits and are for pleasure so dont let others discourage you do what you want itll **** off some jet skiers if you build a 800 horse motor and you push that boat faster than they can go it'd be funny to but have fun with it man heres a link if you havent already chose your path to get you started

http://www.usenginesinc.com/marine-engines.html?gclid=CNPrwYm-x7kCFepFMgod2BoA5w

 

[matt167]

Re: 21' Sea Ray engine swap

Yea. Put a big block to an Alpha and it won't last that long. Mercruiser actually tried, and then they produced the Bravo.. USenginesinc's product info reads like snake oil salesmen. Michigan Motorz is where most get their rebuilt marine engines

 

[Volphin]

Re: 21' Sea Ray engine swap

Then swap to a 454. won't be cheap though. I'm not sure why you don't like the 350. Plenty of power, very reliable.

If you wan't "custom" you could slap a supercharger on the 350, but the outdrive can only handle so much power...

Plus this is a 86 searay.....why in the hell do you want to dump tons of money into it ???? You're going to lose all the money you spend on it. In the end, it will still be a 86 searay lol .....not a custom drag boat ....

If it was my boat project, I'd be stroking that 350 to a 383+, CR 8:1, AL heads, .060 Hyper D pistons, CCams 260, Torquer intake with a whipple blower & Captains call.

Hmmmm. Perhaps I have just made my winter parts list!

 

[LorenHaus]

Re: 21' Sea Ray engine swap

...USenginesinc's product info reads like snake oil salesmen...

HAHAHAHAHA I love this