Project 5.7 to 7.4 swap. Help me to finish it!

[Simonas]

Hello all,
I'm in the project to swap my 5.7 to 7.4. Boat is 1987 Sea Ray Sundancer 268.
I had cracked my 5.7 block, and prior to this it had some knocking noise, so I'm not very interested to change block and hear the same sound again. During the winter, I've bought 7.4 as non runner, and partially incomplete. Disassembled, found stuck rings on one piston, assembled it back, fired up with basic wiring and left it in my shed.
Now the time is coming to get my boat going again, and I think to put that 7.4 in. There are couple of issues with it, and I hope, that with Your help I'll be in the water briefly.
So lets begin with the list, of issues/missing parts:
1. Alternator. I will use it from my 5.7, pulley is different, but I believe I could get one locally.
2. Circulating pump pulley is touching pump itself. Should be there any washer?
3. There's no raw water pump, but as I will use my alpha outdrive, shouldn't be necessary?
4. No cooling hoses. I will come to that later, as I see what could I use from 5.7
5. Fuel pump I will use electric from my 5.7
6. No wiring, or senders. So I will use from my 5.7. What should be added, or possible problems?

Seems all for now.
As I will work on this project everyday, I will post updates and more questions.

Thanks in advance in Your participation.

 

[Bt Doctur]

1 alt is fine
2 No,
3 maybe , almost all BB use the engine mounted Bravo pump
4 plumbing, just the correct hoses and therm housing
5 that should be ok
6 May have to extend some of the wires but should be compatable
7 Need a Bravo engine coupler and rear housing
8 Need a Bravo transom assembly and outdrive

 

[Maclin]

An Alpha is sorta spindly for that 7.4, just sayin'.

 

[AShipShow]

Not saying I disagree with the recommendation for the bravo upgrade but weren't there a few years that mercruiser paired up an alpha with a 7.4?

 

[Bt Doctur]

Only one I knoew of was the 24 BAHA B W/Alpha and had the 1.32-1 ratio and worked best in very light boats

 

[Simonas]

Thank You, guys, for Your inputs.
Why would You suggesting Bravo coupler?
In this boat, originally 7.4 was paired with Alpha one. I know I have to be gentle on the throttle.
I forgot to say, that I'm not aiming at 10 year solution, if it will work for this summer only it's fine for me.

2. Do You have any ideas, why circulating pump pulley is touching pump itself?
4. Thermostat housing looks identical, so I'm going to use 5.7, since it has senders already in. + I know, that thermostat was working fine.

 

[alldodge]

2. Do You have any ideas, why circulating pump pulley is touching pump itself?

Probably because the pump and pulley should not be used together. Pullys and pumps are different between motors. What year is the 7.4?

Thermostat housing should be no issue if it fits

 

[Scott06]

Not just the bravo coupler but suggestion is you upgrade to the bravo outdrive. There were a handful of years that a big block was paired to an alpha drive but it didn't work too well from a longevity stand point. Would reccomend you stay with a 5.7 if you don't want to upgrade the drive.

 

[Simonas]

Probably because the pump and pulley should not be used together. Pullys and pumps are different between motors. What year is the 7.4?

Thermostat housing should be no issue if it fits

I've solved it by placing washers under every bolt, between pulley, and pump. Sounds like a crime, we'll see how it works.

Have put on thermostat, everything looks fine, except it's not pointing exactly straight.

Not sure about year, guessing around '96.

 

[Simonas]

Not just the bravo coupler but suggestion is you upgrade to the bravo outdrive. There were a handful of years that a big block was paired to an alpha drive but it didn't work too well from a longevity stand point. Would reccomend you stay with a 5.7 if you don't want to upgrade the drive.

As I've already told, I'm looking for quick and cheep solution, using what I already have. I know, about 7.4+ alpha problems, and I will be very gentle on the throttle.

 

[Simonas]

Hello again, I've managed to start the engine, and then flood cylinders with hose water. Don't understand how that happened, maybe because I shut the engine first, and water second? Anyway, I've drained it threw plug holes, and all is fine again.
Now I came to the point of putting senders in. How many and what sort should be in 7.4? I'm using my 5.7 senders, but still not sure about some things. Posting pictures with questions.

Also I've found, that starboard side exhaust manifold thread, where drain plug and hose from thermostat comes in, is gone. I can't rethread it, because nobody sells such a big threader. Do You have any other solution, than hammer?

Thanks.

 

[Bondo]

Hello again, I've managed to start the engine, and then flood cylinders with hose water. Don't understand how that happened, maybe because I shut the engine first, and water second?

Ayuh,..... Welcome Aboard,..... My guess is, something is cracked or broken,....

You should be able to leave the water on, Full Blast, without issues,....

Also I've found, that starboard side exhaust manifold thread, where drain plug and hose from thermostat comes in, is gone. I can't rethread it, because nobody sells such a big threader.

Oh, Bullship,.... It's 3/4" pipe threadf, taps are a dime a dozen,....

 

[Simonas]

Ayuh,..... Welcome Aboard,..... My guess is, something is cracked or broken,....

You should be able to leave the water on, Full Blast, without issues,....

Yep, I though the same, but no signs of any cracks. Oil is clean. When did it again, but first shut the engine, and than the hose, no problem. I should add, that I've run it NOT on muffs, but garden hose to the thermostat. (no raw water pump either).

Oh, Bullship,.... It's 3/4" pipe threadf, taps are a dime a dozen,....

I do have pipe angle, for tap replacement, but thread inside manifold is done. Nobody sells such a threader here in Lithuania, or at least couldn't find one.

 

[Simonas]

So no ideas about senders?

Another question:
I'd like to use pulleys from 5.7, which are serpentine belt driven. Problem is that circulating pump will run opposite direction. How does that affect cooling?

 

[alldodge]

So no ideas about senders?

All drives use the same senders, trim limit starboard, trim gauge sender port.

Another question:
I'd like to use pulleys from 5.7, which are serpentine belt driven. Problem is that circulating pump will run opposite direction. How does that affect cooling?

You will have to get a reverse rotation water pump to use the serpentine belt, otherwise it will not move the water

 

[Simonas]

All drives use the same senders, trim limit starboard, trim gauge sender port.

I' talking about engine senders.

You will have to get a reverse rotation water pump to use the serpentine belt, otherwise it will not move the water

I've heard, that many pumps are bi-directional. Do You have any idea how to check it, when it's already on engine?

 

[alldodge]

I' talking about engine senders.

Back of block and above filter are for oil pressure sender and/or oil pressure switch - They are the same.
The knock sender on the side of the block Tee'd with drain - They are different, use one for the motor type
Water temp sender do the same job and will work with gauge just needs to fit location (manifold or thermostat)
Water temp switch is same as temp sender

I've heard, that many pumps are bi-directional. Do You have any idea how to check it, when it's already on engine?

Have not heard that one, but also have never looked into it either