94 Mercuiser 50 Engine replacement

"I have to replace my 94 Alpha

"I have to replace my 94 Alpha 1 Mercruiser 5.0 LX engine serial# 0F138428 Model Number: 450L100GS , I have a alpha 1 outdrive and need a engine to bolt up.
Couple of questions:
Do I need to replace with identical engine and what engine years would work?
Can I go with a vortec 5.0 engine or?
How do you know if it is a short block or long?
How do you tell if its standard rotation or reverse?
Any idesa on were to purchase a quality rebuilt engine or a rebuilt block and use my componets?"

"Are you sure about the model

"Are you sure about the model number? I don't recognize it, but Merc has used some odd model number systems over the years.
I wouldn't waste time replacing the 5.0L. The 5.7L is the same block size, weight, etc, but can deliver up to 325 hp fuel injected; instead of the doggy 210 hp or so of the 5.0L.
How much do you want to spend?
Cheapest route would be a 5.7L base marine motor (short block) from someone like Michigan Motorz at $2549. You would then bolt on your manifolds, starter, alternator, carb, etc.
Better would be a complete 5.7L Vortec Gold 315 hp package long block assembly at $4599.00 this comes with starter, manifolds, 600 cfm carb, alternator, belts, pulleys, and wiring harness. It is all new, not rebuilt, timed, and ready to go.
Merc says the Alpha drive is good for up to 300 hp. You will need to regear it to 1.5 ratio.
I am looking to replace my 4.3L v-6 Alpha One with the same package.
There are other suppliers besides Michigan Motorz. Try a google search for marine engines.
Hope this helps.}"

You have many choices as to wh

You have many choices as to what engine you can install.
It may work best to use a complete 5.7 marine engine.
If you use a short block 5.7 with the heads from the 5.0 the engine may have to much compression for lower octane fuel to work well.
With fuel costing what it does these days it is better to keep away from needing high octane fuels.
The reason the 5.0 heads would bring the compression up is they have a smaller compression chamber compaired to the 5.7. Cheap hp gain but at the extra cost of fuel it may not be worth it.
With flat top marine pistons and small chamber heads you would be at 10- 10.5:1 compression.
Well above what 87 octane would work in.
So if you want cheap hp and do not mind the extra fuel cost put the 5.0 heads on a 5.7 short block and hold on.
Just make sure you get a marine engine and not an automotive engine.

"Thanks Charli,
I think I wi

"Thanks Charli,
I think I will go for a long block, Do you think I should look for a 5.7l instead of the 5.0
I would like to use reg gas 87 octane, If I stay to 5.0 and go with Flat top pistons and a roller cam and lifters would that do much for HP
would I need to use a higher octane gas with this set up. Or would I be better off with a 5.7L , I would like to be about 240 to 260 HP"

If you get the 5.7 depending o

If you get the 5.7 depending on what model you buy it will run ok on 87 octane with 260hp.
A lot has to do with how the boat is used and how it is calibrated.
Sometimes an engine just needs a better grade of fuel. If the engine that you have now ran ok on 87 the 5.7 should as well. Try to find out what the fuel needs of the engine are before you order it.

Just about everyone that needs to replace a 5.0 will spend the little extra it cost for the 5.7.

I'm not sure just why the 5.0 was even used but my guess is it has to do with the rated hp of the boat. Some boats with a 5.7 with the added torque and an extra 40 or 50 hp installed are just plain scary at sea level.
It could be a coast guard safty thing.

If you feel the boat can handle the extra power the 5.7 is the way to go.
Unless you want to spend a lot more I'd stay away from changing too much. The base 5.7 should be fine.

"I'll garauantee you that

"I'll garauantee you that the 5.7--properly propped--will get better gas mileage than a 5.0, and perform better as well. Not sure my anyone would consider a 5.0 when a 5.7 is available for the same boat.

Jeff"