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Grant

5.7L Repower

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Hi Guys,

 I have a 1996 1935SS Cuddy that i have enjoyed for many years now. Unfortunately this past Summer it has finally given up and quit on me. I have been thinking about replacing the 5.7L 2 BBL motor with a new one. The existing 5.7L motor i had a bit of trouble with and was never able to get over about 40mph out of her. Im not sure whether to replace the long block and bolt on my parts or whether to buy a whole big block motor with new 4BBL carb or fuel injected/ EFI etc. Does anyone have any preferences or has done this mod before?

 

Cheers Guys   

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I had a 1930SST with the 5.7L (210HP) and Alpha drive/19 pitch 3-blade stainless. It would hit 49 mph @4600 RPM all day long. It was a great boat! So I think your boat had an underperforming motor.

if you get a long block, you may still have issues if the problem(s) is with the parts (carb) that you transplant. So you might be better off to go with a complete new 5.7 marine crate motor.

And a big block will not fit in a 1935, and the drive will not handle the torque, so that is not an option.

brick

 

 

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If your hull /  shape is a pleasure ?  Go for the all new setup.

It will start faster hot or cold. Should have a revlimiter as standard.  Get the right prop . Makes a huge difference. Too big of a prop WASTES everything the new engine can offer.

Do you have a prop shop with some good LOANER PROPS to try out  No charge around me. 

Power Tech Propellor    www.ptprop.com  is a great place to get some accurate sizing done. Ask for tech support  The exchange program would be very expensive on shipping charges.  I propped for best performance with a full load of + 200 seniors.  Then when I go out alone. The revlimiter saves engine over revving damage while running so lightly.

Edit  They have a great set of free videos on their site to help you. The one about acceleration problems with great top speed  is excellent.

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Hi guys,

Thanks for the speedy reply, when i mentioned the long block i meant the block, heads and all internal parts. I would then have to "bolt on" all the additional parts off of my existing motor, intake manifold brackets, carb etc etc. This is a much less expensive exercise than replacing the whole motor but i am not ruling out that option. I guess if i want a trouble free start and go high performance setup the whole new rig sounds the way to go. As i mentioned above i have a 5.7L with a alpha 1 gen2 drive, would the drive support a higher HP motor? Is a fuel injected engine an option?Is it worth forking our more deer for EFI? 

 

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The Alphas are rated for up to 300 HP. The largest engine offered with the Alpha was the 300 HP 5.7L 350 MAG MPI.

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5 hours ago, tomnjo said:

The Alphas are rated for up to 300 HP. The largest engine offered with the Alpha was the 300 HP 5.7L 350 MAG MPI.

+1

if you go with a long block, I would replace the carb, or at least have the existing rebuilt. You will want to replace the exhaust manifolds and risers, too.  So you might as well just get a complete mercruiser marine crate engine. EFI is great, if it is in the budget.  But there is nothing wrong with  a properly running carb.

What shape is the drive in? You may want to freshen up the u-joints and bellows.

The 1930/1935 series were great boats. If yours is in good shape, a new motor will bring it back to life. 

brick

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I would VERY CAREFULLY  check with Volvo / Mercruiser about your wiring harness & plugs .........ALL............working with a new block or carbs or even a EFI system & sensors.

Wingnut & Shepherd.....

 Can fill you in on odd ball  Things like minimum oil pressure sensor operating correctly to allow the engine to start & run.  Engine swaps & upgrades are.........NOT.......for anyone without that kind of real successful experience. Simple things like a different style electric choke can be a normal mechanics downfall on engine swaps.

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If you want more power, but want to stay with a small block, a 383 stroker motor should allow you to bolt all of the accessories on with no problems. Like already said, it is a good time to replace exhaust manifolds and if you stay with a carburetor it would make sense to go to a 4 barrel.

I'm curious what RPMs you were getting out of the old motor at wide open throttle.

Sounds like a nice project.

 

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Don't know if you are confused with terminology but a big block is like a 454 and up probably wont fit in there, and you might have problems with the alpha drive.  Alphas can survive a regular plain 454 MAG or carb, but probably not an MPI one or one that is hopped up.

 

But yes you could use your engine dressings on your engine and should bolt to a new block.  Like brick said its probably wise to rebuild the carb while in there no need to replace it.  Rebuild kits are 20-30 bucks and somebody can usually do the whole thing if you don't know how for 100 bucks or less.  That type of boat and what your going for I wouldn't even monkey with MPI or fuel injection.

 

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Hi guys,

Thanks again for all of the feedback. My exhaust risers and manifolds were all replaced about 18 months ago and the carb was replaced just before that. I think i will get a partial pack, i.e. long block with new intake manifold, 4 barrel carb and new distributor etc. They are good value for money and should just bolt straight into the rig i have. I should get a bit more HP and trouble free boating for a while. My alpha drive is in good shape and should handle the upgrade ok. I have checked the serial number on my engine and it shows it is a 1996 motor. Can you guys tell me the difference between a pre-vortec and vortec motor apart from the rear main seal etc.  

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I have the big brother to your boat.  Definitely go with a simple 4bbl like the Edlebrock AFM.  It's a simple carb to keep running well.  I replaced with a long block motor, new oil pan, new starter and HO 105 amp marine alternator with fresh valve covers. Motor pushes my 2135 at 48-49 mph on GPS, but I need the 4bbl to get there!  I reused my Thunderbolt ignition.   

Pics are gone thanks to photobucket but the event is posted here:  

 

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Check the fuel pump differences. You might have to convert it to electric.

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On 1/12/2018 at 5:36 PM, Grant said:

Hi guys,

Thanks again for all of the feedback. My exhaust risers and manifolds were all replaced about 18 months ago and the carb was replaced just before that. I think i will get a partial pack, i.e. long block with new intake manifold, 4 barrel carb and new distributor etc. They are good value for money and should just bolt straight into the rig i have. I should get a bit more HP and trouble free boating for a while. My alpha drive is in good shape and should handle the upgrade ok. I have checked the serial number on my engine and it shows it is a 1996 motor. Can you guys tell me the difference between a pre-vortec and vortec motor apart from the rear main seal etc.  

Seeing the boat is a 1996, it is quite likely you have 1987-1995 version unfortunately. For the 1996 and later Gen+ engines, GM primarily changed the head designs allowing for greater power with equivalent fuel economy. Vortec was a label for GM's latest and greatest engine technology for that given time.

Please see below for identification tips for various years of GM small block 5.0L and 5.7L V8 engines (305 and 350 cubic inch displacement)

Mercruiser 5.0l, 5.7l Identification Tips

Over the years there have been several changes to the GM 5.0-Liter and 5.7-Liter engine blocks. Often making it difficult to positively identify which version a technician is working on, and the appropriate parts required to complete appropriate service repairs. Hopefully, this will help to take some of the mystery out of the identification process.

1986 & Earlier
A. All 12 of the intake manifold bolts are installed at a 90-degree angle to the block. 
B. The valve cover bolts are installed at the perimeter of the head.
C. Crankshafts utilize a 2-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: In 1986 there was a limited production run with a one-piece rear-main seal, perimeter valve-cover bolts, and 90-degree bolt pattern for the intake manifold.

1987 thru 19951
A. 8 of the 12 intake manifold bolts are installed at a 90-degree angle to the block. The other 4 bolts are installed at a 72-degree angle.
B. The valve cover bolts are install in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. These blocks are machined to operate a mechanical fuel pump.
Note: During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized this (non-Gen+) designed roller-cam engine.

1996 & Newer (Gen+)
A. All 8 intake manifold bolts are installed vertically. (straight up and down)
See MerCruiser Service Bulletin # 97-1 for proper torque procedures and specification.
B. The valve cover bolts are installedl in the center of the head.
C. Crankshafts utilize a 1-piece rear-main seal.
D. Timing covers are plastic.
E. Engines are fit with electric fuel pumps.
Note 1: During 1996 and 1997 the 3S0-Magnum (carb) and a limited production of the S.7­Liter EFI throttle body utilized the 1987 thru 1995 engine block as stated above.
Note 2: During 1996 the S.7-Liter MPI (multi-port fuel injected) engines were produced with a vapor separator and a mechanical fuel pump. For these applications we recommend using the Mercury Remanufacturing Pro-Series longblock # 860186ROS.

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On 1/12/2018 at 5:36 PM, Grant said:

My exhaust risers and manifolds were all replaced about 18 months ago and the carb was replaced just before that. 

Hi Grant, am I correct in assuming you are currently running a 2 barrel carburetor?

Should this be the case, let me know what version of engine you have and we can talk more specifically regarding parts and power without killing the bank account.

Chris

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From memory, a 1996 version of the “5.7L” had a 2-barrel carb and was rated 210 HP and WOT of 4200 to 4600 RPM.

i had that engine in my 1930SST

brick

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Tha Mag of that era had 4bbl and was rated at 250 hp, which is what I have.

The OP said his 5.7L had 2bbl carb, so probably the 210hp version.

Shepard knows boat parts, he will steer you right!

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Hi 

Shepherd, Brick, Duane and others,

Once again thanks for the valuable info. I have researched my engine and the serial #OF783993 tells me it is a 1995 engine. It definitely has a 2 BBL carb and 12 bolt intake manifold with the centre bolts at a different angle to the outer manifold bolts and a mechanical fuel pump. Not sure but i think i have the Thunderbolt IV distributor? I am definitely going to replace the motor but just trying to determine how far and with what? My options as far as i understand are to get a replacement long block (1995 version i.e pre vortex) and bolt everything i have straight on. Get a part pac with new long block, intake manifold and 4 barrel carburettor and bolt on exhaust and mechanical pump if possible. Or the 3rd option is to get a new Vortec replacement long block with new intake and 4 Bbl carb with more HP? 

Weighing up the pros and cons of each scenario, it would be nice to have more HP for not too much extra fuel consumption but not sure if the last option would fit straight into my boat and what else I would need to replace to get going again?  Additionally I don't have unlimited finds or I would just buy a brand new crate engine?

Anyway I am planning on setting up my boat to remove the engine this weekend. It might take a while as unfortunately am really busy at work. Any thoughts you guys have or experience with repowers would be much appreciated

Cheers, Grant    

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I got a reman from LKQ auto parts build for marine. It. I got the exact same block as that which came out.  However ther were plenty of other options.

Something to think about if yo go with carb, and electric fuel pump; is that it can be challenging to get fuel pressure right across the rpm range.  Too low or to high fuel pressure upsets many carbs, thus the desire to have an engine driven pump, if using a carb.

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On 1/18/2018 at 1:30 AM, Grant said:

Hi 

Shepherd, Brick, Duane and others,

Once again thanks for the valuable info. I have researched my engine and the serial #OF783993 tells me it is a 1995 engine. It definitely has a 2 BBL carb and 12 bolt intake manifold with the centre bolts at a different angle to the outer manifold bolts and a mechanical fuel pump. Not sure but i think i have the Thunderbolt IV distributor? I am definitely going to replace the motor but just trying to determine how far and with what? My options as far as i understand are to get a replacement long block (1995 version i.e pre vortex) and bolt everything i have straight on. Get a part pac with new long block, intake manifold and 4 barrel carburettor and bolt on exhaust and mechanical pump if possible. Or the 3rd option is to get a new Vortec replacement long block with new intake and 4 Bbl carb with more HP? 

Weighing up the pros and cons of each scenario, it would be nice to have more HP for not too much extra fuel consumption but not sure if the last option would fit straight into my boat and what else I would need to replace to get going again?  Additionally I don't have unlimited finds or I would just buy a brand new crate engine?

Anyway I am planning on setting up my boat to remove the engine this weekend. It might take a while as unfortunately am really busy at work. Any thoughts you guys have or experience with repowers would be much appreciated

 

Cheers, Grant    

Gen+ 5.7L so far as I can tell made the same hp with a 2 bbl carb as a 1995 and older 5.7L with 4 bbl carb.  An internal combustion engine is essentially an air pump, and the Gen+ head design worked very well for fuel swirl and scavenging. Do you need a Gen+ and/or do funds required make sense? Much depends on what is available in your area. I have a neighbour mechanic friend up the road who has a direct replacement for your particular engine with 4 bbl carb, etc. (freshwater use only being in 1000 Islands region of Ontario, Canada) 

NOTE: factory Weber carbs from MerCruiser are essentially the same as an Edelbrock marine carb. Parts should be readily available to convert from 2 bbl MerCruiser to 4 bbl set up for whichever generation from MerCruiser.

While we're at it (the 4 most expensive words in the English language) installing an extended swim platform makes that boat so much more user friendly. Not cheap though. Factory ESP off a 210 SSi would bolt right up to your transom. Aftermarket versions are made too.

Lastly, when you pull the engine, HIGHLY recommend removing the 4 lag bolts that hold the forward engine mounts to the stringers, instead of removing the large nut from the tops of the forward PORT and STBD forward engine mounts) This should ensure your engine alignment is as close as possible if doing a direct block replacement, and also makes it easier for placing the engine on say a pallet with blocks of wood for support. Seeing you have an Alpha drive, place the drive in forward gear of course for removal and installation of the drive.

For a better sense of cost, would have the transom bellows, rear shift cable, trim senders, water hose and gimbal ring looked at first. Condition of stringers and transom should be assessed too. Not trying too talk you out of this project, as I rather liked the ride and handling of the 1995 SS versus competitors of that era.

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