Swapping twins.... 4.3 to 5.7 suggestions if anyone has done this pls.

[Pzilly]

Hello fellow money spenders, I mean boat owners.

so this summer has been exceptionally hard on my wallet and mind with boating, already in progress on replacing the 2012 x45 master crafts very expensive ilmor motor, outdrive on the ol reliable 4 winns is in the shop, and now found a crack in one of my 4.3 motors inside the cylinder in my 2760 Regal Cruiser. At this point I think I might go back to instructing skydiving in the summer, that actually pays me, and if it goes wrong nothing to fix anyway plus awesome... LOL

so being that it's end of season I'm going to pull the boat out in two weeks, ive already got the heads off and found my crack, I'm going to pull the rest of the engine soon then over the winter I need to decide what to do, I know there is room in this boat for twin v8s it is a Regal 2760/2860 with twin 4.3 that was also offered with a single big block engine I'm looking for help with setup for installing twin 5.7 V8s in this boat.

Have any of you done something similar? I figure I will need to move motor mounts about 4" which is no big deal, and I'm sure I'll have to re gear the alpha drives and being this boat had the dreaded 1 piece ex manifolds I am guessing reusing my existing Y pipe might be an issue since I had to buy adaptors when I recently switched one to 2 piece hoping that was the water in oil issue.

my 4.3's are EFI and i know the TB is same for 4.3 and 5.7 of those years, I also see they are no longer supported, so trying to find the most cost effective way to do this upgrade, boat is mint, and although I wouldn't say it's under powered for the average boater, for us and all our stuff, towing seadoos, and being a former super charged Baja owner I am seriouly considering this because what caused my issue was 2 cooling ports full of rust which blocked the RV antifreeze from getting into the top part of the block, so chances are the other motor is probably similar, so if I'm switch one, might as well sell a kidney (some one else not mine LOL) and go big. I would seriously have eaten off these two motors, but 18 years seems to have taken a toll on the internal cooling system, and because all cylinder were at 150 psi except the bad one which was still 138 psi, test actually convinced me problem was the 1 piece manifolds at first,me they are still good running...

any input is appreciated, any good jokes to keep my sanity is welcome, donations gladly accepted....

thanks gang!!!

 

[alldodge]

The 4.3's probably move the boat good being it weight at 7800. Going to 5.7's will get it up and going quick. If you like the way it performs now then no need to go 5.7 but assuming there might be some issue, because of the post

I would look for used Y pipes if needed. Assuming you have room in front of the motors. Going to carbs would be easiest unless you want to go the reflash the ECM route.

 

[achris]

... and I'm sure I'll have to re gear the alpha drives ...

Not necessarily. Those drives should be 1.62:1, and for a V8 stock ratio is 1.47:1. Not really a big difference, and the advantage of the 1.62's is that you'd be running more pitch, so better efficiency.

If you go the 5.7 route, stick with the 1.62's and see how it goes. I suspect a prop change is all you'd need.

Chris.......

 

[Scott06]

Not necessarily. Those drives should be 1.62:1, and for a V8 stock ratio is 1.47:1. Not really a big difference, and the advantage of the 1.62's is that you'd be running more pitch, so better efficiency.

If you go the 5.7 route, stick with the 1.62's and see how it goes. I suspect a prop change is all you'd need.

Chris.......

did a similar swap on single engine boat 4.3 for 5.0, as mentioned will be easiest if you go back in with carbed engines. I was able to get a partial engine package plus exhaust manifolds from Michigan motors. Swapped all my front and back accessories from old to new engines- coupler, starter, flywheel cover, wiring harness, ps, alternator, fuel pump, motor mounts. Etc. side motor mounts will be 4" forward likely if your boat was offered with a V8 the stringers will be there. You'll need 4" in front of the engine as well.

Things i I had to change exhaust elbows between risers and y pipe, distributor is the same just need a V8 triggerwheel cap and rotor, V8 ignition module for TBV.

Per Chris's comments I kept my original 1.81 ratio drive, works perfect with 2" more pitch -19" to 21".

 

[Pzilly]

Right on, thanks for all the help you guys are tossing out.


Boat on the v6's does ok, probably just me used to single IO boats and performance boats, if I could find some 250 HP 4.3s I'd probably do that, I pretty much just want more torque for planning out and I am constructing a sea doo towing rig so seems wrong not to do this, as mentioned the boat is a solid 9 cosmetically, my buddy ran a high end body shop and he even waxes the trailer that literally only goes a half mile a year from ramp to the yard, so my mindset is take this cruiser and make it better, of course money comes into play, especially w twins.

i have a good 12" in front of the motors, just researching fuel, controls, wiring harness and exhaust mostly.

my biggest concerns have been, fuel system and wiring harness, seems my efi TB is same for both 4.3 and 5.7 for these years but looks like ECU is different and no longer supported, so debating going to carbs, would like to stay FI but not sure how the wiring harness is going to work out? Do you all feel ditching the FI and going carbs is ok? My 800HP Merc whipple charged 502 back 15 years ago was carbed, just seems a step back going from EFI fo carbs, but then again this EFI is pretty basic, not sure what would be involved in going MPI?

glad to hear changing the props might be enough, my buddy who owned the boat previously gave me a set of 19 pitch 4 blades, and then a set of 21 pitch 3 blades, boat runs and planes easily on the 4B 19 tops out at 38mph at 4800 rpm, when light load the 21 3Bs take a bit to plane have to use tabs but runs 43 at 4300 rpm so maybe my 21s could now be for heavy and grab some 23s. And sell the 19s,,after some testing of course lol.

thanks again for info so far, if any other thoughts I'm all ears...

 

[achris]

... just seems a step back going from EFI to carbs, but then again this EFI is pretty basic, not sure what would be involved in going MPI?

Completely agree here. I had a 4.3LX (carbed) before the 4.3MPI, and I wouldn't have another carbed engine, ever!

glad to hear changing the props might be enough, my buddy who owned the boat previously gave me a set of 19 pitch 4 blades, and then a set of 21 pitch 3 blades, boat runs and planes easily on the 4B 19 tops out at 38mph at 4800 rpm, when light load the 21 3Bs take a bit to plane have to use tabs but runs 43 at 4300 rpm so maybe my 21s could now be for heavy and grab some 23s. And sell the 19s,,after some testing of course lol.

thanks again for info so far, if any other thoughts I'm all ears...

Stay with the props that take you into the top half of the rev range. Those 21s on the 4.3 that only got you 4300, don't do that to engines, it damages them... Better to be 100 (or 200) over the top then under...

I'd look at drop-in 5.7MPIs... Plenty out there... And not that expensive. I have no idea what your budget is...

Chris......

 

[alldodge]

my biggest concerns have been, fuel system and wiring harness, seems my efi TB is same for both 4.3 and 5.7 for these years but looks like ECU is different and no longer supported, so debating going to carbs, would like to stay FI but not sure how the wiring harness is going to work out?

The TB and ECM are the same in appearance, the difference is the coding done with the ECM. You can have the ECM reflashed for the standard 5.7 (OBD Diagnostics), or can fine tune it with AFR meters and MEFI Burn SW

 

[tank1949]

Hello fellow money spenders, I mean boat owners.

so this summer has been exceptionally hard on my wallet and mind with boating, already in progress on replacing the 2012 x45 master crafts very expensive ilmor motor, outdrive on the ol reliable 4 winns is in the shop, and now found a crack in one of my 4.3 motors inside the cylinder in my 2760 Regal Cruiser. At this point I think I might go back to instructing skydiving in the summer, that actually pays me, and if it goes wrong nothing to fix anyway plus awesome... LOL

so being that it's end of season I'm going to pull the boat out in two weeks, ive already got the heads off and found my crack, I'm going to pull the rest of the engine soon then over the winter I need to decide what to do, I know there is room in this boat for twin v8s it is a Regal 2760/2860 with twin 4.3 that was also offered with a single big block engine I'm looking for help with setup for installing twin 5.7 V8s in this boat.

Have any of you done something similar? I figure I will need to move motor mounts about 4" which is no big deal, and I'm sure I'll have to re gear the alpha drives and being this boat had the dreaded 1 piece ex manifolds I am guessing reusing my existing Y pipe might be an issue since I had to buy adaptors when I recently switched one to 2 piece hoping that was the water in oil issue.

my 4.3's are EFI and i know the TB is same for 4.3 and 5.7 of those years, I also see they are no longer supported, so trying to find the most cost effective way to do this upgrade, boat is mint, and although I wouldn't say it's under powered for the average boater, for us and all our stuff, towing seadoos, and being a former super charged Baja owner I am seriouly considering this because what caused my issue was 2 cooling ports full of rust which blocked the RV antifreeze from getting into the top part of the block, so chances are the other motor is probably similar, so if I'm switch one, might as well sell a kidney (some one else not mine LOL) and go big. I would seriously have eaten off these two motors, but 18 years seems to have taken a toll on the internal cooling system, and because all cylinder were at 150 psi except the bad one which was still 138 psi, test actually convinced me problem was the 1 piece manifolds at first,me they are still good running...

any input is appreciated, any good jokes to keep my sanity is welcome, donations gladly accepted....

thanks gang!!!

Upgrading to 5.7(s) will cost you a lot of time and LOTS of extra parts that you will have to find: distributor, brackets, exhausts, etc. Will the 4.3 closed cooling system be sufficient for the 5.7s? You may need a larger heat exchanger. The boating season is winding down so you might want to contact insurance company salvage yards for parts/motors. Usually, the ODs perform the counter rotation, but you may also have to find a marine 5.7 counter rotating engine? Converting automotive engines to marine engines is not that difficult if you want to start from scratch. But, you will still have to locate all the other add-ons. I'd google marine salvage or any insurance company that insures boats and query them for a "turn-key" 5.7(s). You may have to drive to their location and test the motors. Make sure they run, have good oil pressure, etc. You may have to spend the night at a motel to perform proper testing, or you can spend 4-6 K per motor for a NEW complete set-up. Oh and while motors are out, make damn sure your transom is not full of ROT! TRUST ME!

 

[Pzilly]

Completely agree here. I had a 4.3LX (carbed) before the 4.3MPI, and I wouldn't have another carbed engine, ever!



Stay with the props that take you into the top half of the rev range. Those 21s on the 4.3 that only got you 4300, don't do that to engines, it damages them... Better to be 100 (or 200) over the top then under...

I'd look at drop-in 5.7MPIs... Plenty out there... And not that expensive. I have no idea what your budget is...

Chris......

Hey Chris,
where do you recommend looking for the 5.7s? Been out of the boat scene for 10 years.

isn't budget always subjective and a rabbit hole of rationality hahaha?

if I can figure out a way to move my efi over then I would be on target with my budget, I look at it this way, if I have to replace my 1 piece manifolds on the good motor that's 1200 plus a new 4.3 long block would be another 3000, so I would already be in 4200.00, if I could source a complete 5.7 w manifolds for 6ish I would be ok with that, plus I think it would be cool to out run my buddies fountain 38 sport cruiser with a 28' regal Express cruiser hahahaha

 

[achris]

A site referred to by another forum member has both new and remanned engines. I think you could sell off one of your 4.3s complete and it 'should' fetch a good price. That would leave you with parting out the other. Although a remanned 5.7MPI isn't as cheap as I thought... http://centerstateengine.com/remanufactured-marine-engines/mercruiser-5.7l-alpha-4v-clone/

Just getting a base engine and trying to move the current 4.3 EFI (throttle body injection, not MPI) across is not going to be easy, or cheap.

Here's a complete drop-in, with manifolds, for a couple of K less. http://centerstateengine.com/remanufactured-marine-engines/mercruiser-4.3l-alpha-4v-clone/

Interestingly, I haven't been looking at new/remanned pricing for a couple of years. They have taken a serious hike!

Chris..........

 

[Pzilly]

Thanks Chris and everyone,
got it out today, got to love a red head wife who runs the chain fall hoist hanging off the excavator bucket hahaha pay no mind to the boat name, its my buddy I bought the boat from name, I don't name boats and haven't gotten around to removing it.

still weighing my options, but odds are high on the 5.7s....

anyone ever deal with Eagle engines? My uncle in law is a long time marine mechanic and he can get me enhanced long blocks from them pretty reasonable.

 

[Scott Danforth]

TBI was a poor excuse for injection. It was a sloppy electric carburetor.

From a reliability standpoint, actually worse than a carb

I would pick up new crate motors, new exhaust manifolds and risers, go with a carbed intake,Voyager dizzy, move your accessory drive over.

Then modify your existing wiring harness and move that over.

Existing HX on a 4.3 no where large enough for a 5.7. So plan on buying two new heat exchangers

 

[Lou C]

For the bad engine, you could just buy a reman short block, get the heads checked out, if they are good, install them on the new short block and put it all back together. That's about the most cost effective way to solve this problem. Your engines had closed cooling so the intakes and cyl heads should be clean and not corroded inside.
I can see for sure the desire to have twin 5.7s in a boat that size, but as we all eventually find out conversions are full of little parts that we now need that run the cost up. If the other 4.3 is in good shape why not either repair (if feasible) or replace the one that's giving trouble?
As far as carbs vs throttle body fuel injection, I think it depends on what you are used to. If you grew up with carbs like I did and are used to the quirks of Quadrajets, Holleys and Carters, then having a carbed boat is no big deal and you don't have to deal with the manufacturer's lousy habit of making certain mission critical parts NLA, and they all do it sooner or later. The beauty of carbs is that you can buy them NEW in the aftermarket (except our beloved Quadrajet), and keep on boating. I am still running a 31 year old Quadrajet that runs excellent, when clean and set up right.
But if you grew up with cars that had throttle body injection or better yet port EFI you will think carbs are crude and ill mannered, that I can see.
Whatever you do there a lot of good choices.

 

[Scott Danforth]

The beauty of carbs is that you can buy them NEW in the aftermarket (except our beloved Quadrajet), .

the Edelbrock carbs are basically Q-jets

 

[Lou C]

Scott, I know Edelbrock made a Q-Jet copy for some years but what they are selling now (1409) is a version of the Weber carb used by Merc which itself is a version of the old Carter 4bbl I think. Of the three, Holley, Edelbrock or Q-Jet, to me the Q-jet is the most sophisticated. The small primaries and huge secondaries work great for low speed responsiveness and top end power. I was always amazed how economical my 4.3 Q-jet was compared to other boats. I tried a Holley 4160 on my boat and despite being brand new and set up for the 4.3 it just would not run right. A couple hrs cleaning the old QJet and new gaskets and 100% back to running great.

 

[Scott Danforth]

the 4160 is a compromise for a carb. either 4150 (square) or a 4175 (spread) would be my choice. Then again, I was looking at an 8x1 manifold the other day with 8 Stromberg BX's on it

if only it was marine approved.....

 

[Lou C]

Would have tried the spread 4175 but would not clear the thermostat housing due to fuel inlet in front instead of side.
The 4160 specified for the OMC and Volvo V6s was different in that there was no power valve at all, and the main jets were a bit richer to compensate.
https://www.holley.com/products/fuel_systems/carburetors/marine_carburetors/parts/0-80492

here's the one I tried, don't know if I got a bad one or not but it ran super rich, loading up, surging etc. I took the bowls off, checked floats and needle valves, all good there, made sure the idle transfer slot was not over exposed, etc. Nothing the Holley techs told me to try made a difference. Then after I had already replaced it with the original Q Jet I took it apart again, carefully blew out all the passages in the metering block (primary), nothing seemed clogged. When I got to the rear, (metering plate) what I found was...all the special clutch bolts holding it on, were loose, like barely hand tight. Don't think that caused the problem though. So its sitting in the Holley box on a shelf in my garage, still a mystery. Meanwhile the 31 year old Q-Jet works just fine.