4.3 to 5.7s

fletcho5

fletcho5

Member
Dec 22, 2012
34
Vancouver washington
Boat Info
1987 amberjack hardtop, 1 ton v10, garnim4210, autopilot, espar heating,
Engines
twin v6 550 hrs
has any one repowered there 270 amberjack with 4.3s to 5.7s and what are the problems if any.
 
Well a 4.3 is basically a 5.7 with 2 less cylinders. You might have to move the forward motor mounts after making sure you have enough room forward for the longer engines. I also believe the 4.3 outdrive has a different gear ratio than the 5.7s
 
if there are any electrical control modules for the engine/ignition they will likely need to be replaced....

cliff
 
Are your current outdrives strong enough to handle the additional power? Potentially 300 hp depending on which 5.7 you choose?
 
fletch, I'd question your idea of swapping engines because you have a 20 year old boat and that just seem to make sense from an economic standpoint.

I'm not ridiculing your boat because of it's age--mine is older than yours.

I'm just thinking it might be a lot less expensive and a lot fewer headaches to start a search for a boat that already has the engines you want.

Spending a fortune reinventing the wheel in your case just doesn't seem to make sense.
 
I agree with Mike.... This will cost you $8-10,000 dollars if you do most of the work yourself. You will have to buy complete engines as very little few parts from the 4.3s will work on the 5.7s....maybe the carbs and the wiring harnesses to the instrument panel. And most likely change, at minimum, the gear ratio in the drives. And when you are done you will still have a 30-year old boat.

I've always believed the least expensive way to make a boat go faster is to buy a faster boat.
 
Espos4 said:
Are your current outdrives strong enough to handle the additional power? Potentially 300 hp depending on which 5.7 you choose?
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Unmodified, standard, carbureted 5.7s are typically 260HP. A very common package with the Merc Alpha drive. If he was going to Magnums, Bravo I's would be in order as the Alpha is only good for about 300HP. However, SEI claims their SEI106 will handle more than 300HP but he would still be changing the drives but at least the Gimbal Housings would stay the same and accept the SEI drives.

I dunno Fletcho this seems like one to run away from. I don't think you would see more than 4-6 MPH increase in speed anyway and a bit of an increase in fuel economy. Can it be done? Sure. Should it be done? Probably not.
 
thanks for all the thoughts I already plan on installing new alpha 1 gen 2 outdrives and was thinking I could add 80 hp over the 4.3 for almost the same money. I would have to add on to the motor mount area not to hard have plenty of room in front of the 4.3 to add the 4.5 inches for the 5.7s also would do fuel injection. I figured this would run close to 20,000 but to replace the boat new would be outrageous. This would make the boat like new. Have already done interior, dash with new 12" Garmin and new gauges,electronics with tower, swim platform, polished the whole boat,windows and cabin walls, and bottom paint. Would be all in about 45,000 in a 270 amberjack with hardtop kind of made sense to me?

thanks fletch
 
Should go really fast. We had 3.8 V6s in a 28 footer (water line) that had upper and lower helm boat had beam of 10.5 feet. Weight was about 8,000 pounds I was told. I felt it was under powered. I wanted to put in the 4.2 as other people had similar size boats with the 4.2 and had more power. Our boat would do 22 knots at 3,800 RPM and burnt 1 liter a minute. Top speed was about 27 knots at 4,200 RPM. I have a 5.7 in our jet boat that is 7.5 feet beam and 21 long. The engine has 330HP and has lots of power. If you put them in your boat I would be worried about the structural integrity of your boat. It is like putting bigger engines on a aircraft, the wings could fall off. Perhaps SeaRay could comment if your boat would stay together also I would worry that your insurance might not cover you if your boat sank due to a structural failure.
 
fletcho5 said:
I figured this would run close to 20,000 but to replace the boat new would be outrageous. This would make the boat like new. Have already done interior, dash with new 12" Garmin and new gauges,electronics with tower, swim platform, polished the whole boat,windows and cabin walls, and bottom paint. Would be all in about 45,000 in a 270 amberjack with hardtop kind of made sense to me.
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Fletcho, a friend of mine has a 268 Sundancer, not sure what year, but he has spent a FORTUNE upgrading it. New genny, new air conditioning system, bow and stern thrusters, complete new interiors, etc. He says he's in the boat about $90K and knows it's worth about $20-$25K but he's got more money than anyone ought to have and he doesn't care. I want to buy his boat when he's ready to sell it.

In your situation, why must you have a new boat? Rather than look at new, why not pick one that's NEWER than your boat and has the engines you want? That way you're not laying out the big bucks for the engine swap and pouring money into a hole. Pour that money into a newer boat equipped the way you want.

I understand it's gonna be tough to part with your baby after all the work you've put into it, but to throw more money at it just doesn't make any kind of sense. But that's just my humble opinion.
 
I mostly agree with the idea of buying a boat with the engines you want. It is usually the more financially sound decision. But the really sound financial decision is not buying a boat at all.

There can be some real benefits to a re-power if you really love the boat you have. You can get the power you want to make the boat perform the way it should. Sometimes the boats you want never came with the power you want. Additionally, in the case of re-powering with brand new engines, you can get mechanical reliability beyond what a "newer" boat with still used motors offers.

Having said all that, I would make the decision to re-power very, very carefully, and only after investigating a multitude of other options, because the numbers can be harsh.
 
I plan on owning the boat about ten more years and then downsizing to a 8' beam boat. Buying a used boat is a used boat
I'm looking for ten years of trouble free boating. When running 40 or 50 miles off shore for tuna is not were you want to loose a motor.
I've looked for a used boat with a ten foot beam and 30 feet long can't do for 50 grand and hope for dependability for the long term
the 270's came with 5.7 I guess as an option when new. Not looking for speed trying to get a little more hole shot boat is a little slow with Ice and coolers and fish bags and gear getting out of the hole.Maybe someone has the 350's in there amberjack and could weigh in on performance numbers carb or mpi injection.
Have not had any problems with carbs except at cold start up, have to pump the throttles a couple times. that's the mpi thought.
Hard decision
fletch
 
I've been looking at boats since I sold the 52 footer in CA and moved to the Gulf Coast. I don't know about Vancouver but down here for $50k you can get a fairly new 30 footer with a 10' beam....and still have $10-15K to play with. why does it have to be new?
http://www.yachtworld.com/boats/200...3013063/Dunedin/FL/United-States#.Wd2iS7qcF9A
Or you could do this one and quit screwing around. You could probably get it for $50,000 plus shipping. A bit more than you mentioned but pretty sweet and a 13' beam
http://www.yachtworld.com/boats/199.../Ft.-Lauderdale/FL/United-States#.Wd2jxbqcF9A

I personally would not spend $25k to repower a 30 year old boat. Yeah, I know you really like the boat and just got it the way you want it. But it's still a 30 year old boat and in 10 years t will be a 40 year old boat. And who am I to talk as I am restoring a 32 year old Cobalt....but when mine is all done I won't have close to $25k in it.

Look....in the end, it's your money and you will do what you choose but there are some pretty knowledgeable people here advising against it. If you were sure it was the right thing to do why would you come on the forum and ask for advice? You must have some doubts.

As I said, its your money. I sincerely hope it all works out for you which ever way you go. If you do repower what a great time to make the engine room a jewel.

Shawn
 
If you are replacing gen 1 with gen 2 drives, the whole transom assembly also requires replacing. Pretty much everything from belts to props. As far as the outdrives go, you may want to consider the bravo line as well. Only have to drill 2 holes and add engine mounted raw water pumps. They are rated for 400 hp I believe. If you can find a couple "take outs" from outboard conversions that were behind small blocks, they will make a much more solid combination. Just another thought for you.
I did this a couple years ago for about $3000 (Can) with a B2. Included new OEM gimbal brg, u joint, bellows, shift cable, senders, paint and some elbow grease.
 
Thornton69 said:
If you are replacing gen 1 with gen 2 drives, the whole transom assembly also requires replacing. Pretty much everything from belts to props. As far as the outdrives go, you may want to consider the bravo line as well. Only have to drill 2 holes and add engine mounted raw water pumps. They are rated for 400 hp I believe. If you can find a couple "take outs" from outboard conversions that were behind small blocks, they will make a much more solid combination. Just another thought for you.
I did this a couple years ago for about $3000 (Can) with a B2. Included new OEM gimbal brg, u joint, bellows, shift cable, senders, paint and some elbow grease.
Click to expand...
Now that is a good idea....
 
I really like the best thing is not buy a boat butttt, still have one
getting a couple quotes on new alpha 1,s complete and 5.7s trim pumps and y pipes. one of the dealers suggested the sei outdrives and could save a lot. any opinion's on the quality of the sei,s to include the paint and saltwater I heard there not good in saltwater.
appreciate all the comments but a bot with 700 hrs is still used boat and unpredictable.
thanks fletch
 
fletcho5 said:
any opinion's on the quality of the sei,s to include the paint and saltwater I heard there not good in saltwater.
Click to expand...
I have an SEI106 outdrive on my 1985 Cobalt. That boat lived in salt water in Long Beach it's entire life minus the last 2 years I have been restoring it. The drive was 2 years old when I pulled the boat out of the water and moved it to Northern Cal and then here to Southern Louisiana. When I pulled the boat the drive looked fine. Nothing unexpected. Some very slight surface corrosion. A little sand paper and a rattle can of Phantom Black and it looks good as new.

I also pulled the drive to replace the bellows and a couple of things happened. First, the Merc gimbal housing literally crumbled in my hands. It was original and 28 years of a salt water environment finally took its toll so I had to replace it. Second, when the drive came out I discovered there had been a small leak in the drive shaft bellows and the entire drive shaft and u-joints were crusted with salt. I wish I could find the pictures. It looked so bad that I was sure I would need to replace the outdrive. So I rinsed the crust off, hit it with a wire brush on a Dremel and it all cleaned up. There was no corrosion, no pitting....nothing. To be safe I opened the u-joints, cleaned and re-greased the bearings and put it back together. Pretty good testament to SEI drives and their durability. I can honestly say that I would not hesitate to purchase and install the SEI drives on my boat. And if I were doing what you are doing I would definitely install the SEIs.
I also separated the upper and lower units to replace the water pump. I installed a Sierra pump and I could not tell I was not working on a Merc. You could look at installing a Mercathode system if you want some insurance.

So it looks like you are going forward with this ill-advised engine swap. If you are, take lots of pics. Good luck.

Shawn
 
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