Merc 5.0 EFI Alpha - Cracked Block. What are my options?

[LambChop]

I scored an excellent deal on a '98 Chaparral 2130 SS. Why was the deal so good? The block of the Mercruiser 5.0 EFI cracked after a poorly executed winterization. The crack wasn't terrible, but nonetheless, it is a crack. The previous owner weighed his options and decided to try repairing the block using liquid metal before spending the money on a new motor.

The boat has had 2 seasons on it since the repair and runs perfectly. I've personally driven it for 8 hours since purchasing it. There is no water in the oil, no oil in the bilge, and no signs of oil in the exhaust water. The motor runs excellently.

Yes, I knew the block was cracked before I bought the boat; I test drove the boat before I bought it and checked all the fluids for signs of water intrusion. The boat is in fantastic condition and still worth more than the price I paid for it.

I'd like to get a head start on a replacement motor.

While the 5.0 EFI does alright, I think it could use another 30-35 hp. I have an Alpha drive, so it seems I'm limited to 300 hp (or less).

I'd like to stay with EFI.

Will a 305 intake manifold and fuel injection system work with a 350 long block? Would I be better off just picking up a 305 short block/long block? Is the best option to pick up a 350 short block and use the rest of the parts from my current 305 to complete it?

Let's hear what you guys would do if you were looking to get a bit more power for as little coin as possible.

Thanks,

Adam

[Failproof]

Get a 350 long block ready. Go vortec. Get the matching manifold for what induction system you have to the vortec heads. But honestly, if the fix is holding, and you dont mind smoking the engine when it does let go (and ruining your outing) just run it. Its a 5.0 and not worth worrying about. It wont ruin anything you would be re-using when it does go.

[LambChop]

Driving it 'til it dies is the plan. I know it's not if, but when... or perhaps the repair may hold for quite some time?

Will the fuel injection system (throttle body injection) from the 5.0 work with a 350 long block (given the right intake manifold)? I guess I have no idea what comprises the 5.0 EFI's fuel injection system - whether the injectors are big enough for a 350 w/ Vortech heads and how the ECU senses how long to keep the injectors open.

- Adam

[Failproof]

Yes the FI will work. May need the larger injectors (2 of them in the TB) may need a different flash on the ecu/pcm. Not sure on that one though.

[edsmax]

Yes, you can swap TBI setup to a new 350 block but you will need the larger injectors that were used on the 5.7 260HP TBI setups.

Personally, I would either get a new drop in complete motor. Another option would be to get a new vortec compatible manifold for your new long block and put on a 4V marine carb (Edelbrock 1410).

I had that same motor on my boat originally (305 TBI 240HP) and it was a dog. Do research on MPI vs TBI vs 4V before you make any final decisions. I went from TBI to 4V and have much more power and getting comparable fuel consumption levels.

[TilliamWe]

Is your 5.0 actually already a Vortec engine? Right in 1996-1997 they used botrh Vortec and non-Vortec.
If your current 5.0 is NOT a Vortec, upgrading to a Vortec 5.0 long block will make a big difference. If what you have is already a Vortec, going to a 5.7 Vortec is the way to go.
I personnaly liked TBI. And my 1997 5.7LX EFI Gen + engine was a TBI Vortec, and rated at 280hp. It ran GOOD!

[LambChop]

Is your 5.0 actually already a Vortec engine? Right in 1996-1997 they used botrh Vortec and non-Vortec.
If your current 5.0 is NOT a Vortec, upgrading to a Vortec 5.0 long block will make a big difference. If what you have is already a Vortec, going to a 5.7 Vortec is the way to go.
I personnaly liked TBI. And my 1997 5.7LX EFI Gen + engine was a TBI Vortec, and rated at 280hp. It ran GOOD!

Any tips on how to identify whether the engine is a Vortec or not?

[Bond-o]

Any tips on how to identify whether the engine is a Vortec or not?

Ayuh,... Count the intake bolts,... Vortec has 4 on a side, 'n others have 6 per side...

[TilliamWe]

Ayuh,... Count the intake bolts,... Vortec has 4 on a side, 'n others have 6 per side...

exactly, and they are straight up and down, in relation to the earth.

[LambChop]

But honestly, if the fix is holding, and you dont mind smoking the engine when it does let go (and ruining your outing) just run it. Its a 5.0 and not worth worrying about. It wont ruin anything you would be re-using when it does go.

Just put another 3 hours on the boat tonight and it ran perfect. The temp gauge fluctuated a couple times up to 180º, but I think that was due to weeds (lots of weeds where the boat was run). The oil pressure was perfect the whole time.

I'm thinking I'll hold off on building a new motor for now and put a few bucks into a better prop. The boat currently has an aluminum 3 blade on it (not sure what pitch) and it turns between 5,000 and 5,200 RPM at WOT. I'm pretty sure the 5.0 is supposed to turn between 4,400 and 4,800 WOT, so it seems that I have a shallow pitch prop. The speedometer currently is not functional, but I'm going to see if I can remedy that tomorrow. If not, the boat is getting a new GPS speedometer.

I'd still like to hear ideas on a replacement motor - the current suggestions have been great. Whether or not the liquid steel patch fails, it's still a boat. Boats and water don't play well together...

I come from a motorcycle background, so I have a decent gauge on wrenching, but small block Chevy compatibility/building isn't my strong suit. Yet... I have access to marine parts at wholesale, a heated shop, an engine stand, ceiling mounted winch, a plethora of tools (as well as a few machinist friends), and a fork lift, so I think I've got the resources to take care of replacing the engine myself.

- Adam