My Money pit

[hobby10k]

93' 5.7 mercruiser in sea Ray

On top of repairing the floor I Pulled risers and manifold to change them before this season and well, it was too late and the risers has been leaking into the engine all winter. Pulled intake and heads off and sure enough it pitted the cylinder walls.

Since I have to get a new engine (pitting might be too deep for rebuild anyways) I'm just going to throw a newer 5.7 vortec into the boat.

It should be a direct bolt in right? I know I'll need to get a new intake, But other than that everything else should be direct fit right? Will any 5.7 work, or must it be a marine engine?

Thanks in advance for your help.

 

[Rick Stephens]

Truck engine is fine. You don't want anything but a mild cam, like a stock pickup cam. Most all your Mercruiser stuff is direct crossover. Vortec has different pan, front timing cover, will have balance shaft, and as you knew, a different intake. If your '93 has a mechanical fuel pump, the Vortec won't have a place to attach a mechanical, have to go electric. Not a huge deal but takes some wiring. Later Vortecs will have serpentine belts, good thing, except your '93 is probably v-belts. You will need new water pump - automotive water pumps are designed for running antifreeze, if your boat is freshwater cooled you will need one designed to not rust so much.

 

[thumpar]

You will also need all the electronics off the old motor. Alternator, starter, distributor, ect need to be marine rated. Hopefully those are good on the old motor and will work. Core plugs will need to be switched to brass. Along with the electric fuel pump you will need to add an oil pressure switch. I am sure I probably missed something. Rick is right though. A truck motor is the way to go.

 

[hobby10k]

Ok so just a few miner things that's good. Truck a 4 bolt? What numbers would indicate it being a truck vs car engine?

Long block won't have pan and covers and stuff so I'll get that stuff somewhere and as far as electronics, it ran when I parked it last so they should all be good. Bought a new alternator when I bought risers so hopefully I can change the pully and not have to buy another new alternator.

Didn't think about fuel pump, but electric pump will be easy install.

I have closed cooling so good to go on auto water pump. Unfortunately I also bought one of those to change on my engine too, so will have to buy another new one with serp pully.

Oil pressure switch? Explain a little about adding pressure switch.

There is someone I found online about 1.5 hrs from me that has rebuilt vortecs for $1500 hitting him up about getting one from him.

 

[NHGuy]

I have just redone a vortec block for my boat.

None of the 5.7's have balance shafts, and the pan is actually the same. Just pay attention to which side dipstick bump out.

If you get a truck block, and you should; swap the harmonic damper from the boat engine onto it. The fuel injected TBI unit has it's mark in a different spot. Neither one is a balancer, they're just dampers. The balance happens at the flywheel and inside. If you can't swap out the boat damper you can re-mark the truck unit once you have TDC.

You can bolt an electric pump where the mechanical one was. They are designed for it.

The oil pressure switch can be tee'd in to either of the current oil pressure sensor points with npt or mip tubing from the hardware store and a little bit of liquid thread sealer. Don't use teflon tape. By the way, MIP is the same as NPT.

That oil pressure switch powers your electric fuel pump. More importantly, it cuts your pump power when the engine stops so you don't get a bilge full of gasoline.

I'd reuse whatever belt system you take off the bad engine. The serpentine brackets, pumps and pulleys are different. The serpentine water pump spins the other way.
It's easy to mix up vortec cooling because the aluminum Corvette vortec system from which it evolved has reverse cooling. Not so with our iron motors.

You will need stainless head gaskets and brass core plugs. Try for a compression ratio and good quench in your gasket selection. It's free horsepower.
Only thing is GM uses those dished pistons which defeats much of the quench benefit.

Get a package of SAE thread chasers off ebay for $15. Run them into every hole you can reach. That will save you lots of grief later.

Don't forget to put thread sealer on the head bolts that enter the cooling system otherwise coolant will wick up the bolts.

 

[Rick Stephens]

That's right, no balance shaft on V8. My brain shifts back and forth and kills a few more cells every time.

NH Guy nails the rest of that.... you probably don't need stainless head gaskets or brass freeze plugs on a closed cooling system if you don't want em. Your engine cooling system is no different than automotive in this case.


Just went through building in the electric fuel pump electrical system for a Vortec in a '93 boat. It is nice to do it while the engine is sitting on the motor stand. I had the motor running to test everything before I stuck it in the boat. Tweaked it a couple times to make it more robust and to bracket mount a solenoid to power the pump. In the end, with some shrink tube, shrink fit sealed connectors, wire loom, and a sealed solenoid, was able to duplicate the Merc system so it even looks factory. You cannot just slap this together and expect it to be either safe or reliable.

I used the OEM Airtex fuel pump and then ordered OEM parts like pump mounting bracket and fuel lines.
https://www.amazon.com/gp/product/B0076D5NVK/ref=s9_simh_gw_g263_i4_r?ie=UTF8

Rick

 

[NHGuy]

I used the Airtex for the 454 motors (cause I built a gas hog) and the bracket that came with it fit the SBC.
In 98, the year after my engine, Mercruiser started to go with electric pumps, so if you follow that design it will be factory and easy to keep organized. That system uses a fused power supply to the pump.
But Rick has a good point, a fused solenoid to power the pump is better.

Rick is right about the stainless & brass too. I forgot you are closed cooling.

 

[hobby10k]

Thank you guys so much! Wealth of knowledge and help. I will reference this thread throughout the engine swap. Hope I can get this all done in a decent amount of time.

 

[hobby10k]

Spoke to the builder, and he has some on hand but also will be building more. Is there a particular cam I could get to boost power in the RPM range for boat? Can probably have him out the parts needed for engine off of mine as well. So I can have the builder build exactly as needed.

 

[Rick Stephens]

Keep checking in. Lots of details and no reason you should duplicate the false starts that NHGuy and I went through.

 

[hobby10k]

Any tips on cam selection for the engine builder to put in?

Spoke to the builder, and he has some on hand but also will be building more. Is there a particular cam I could get to boost power in the RPM range for boat? Can probably have him out the parts needed for engine off of mine as well. So I can have the builder build exactly as needed.

 

[Bondo]

Any tips on cam selection for the engine builder to put in? .

Ayuh,..... Yer lookin' for idle to 5,000 rpms,..... Don't go nuts with it,..... 214?, 218?,..... an RV cam,....

 

[hobby10k]

ok, thank you. I figured I might as well do things for power upgrades while I have it all tore apart.

 

[NHGuy]

Oh you can build it strong...use d dish pistons. get a .040" quench distance. Keep your compression below 10. ideally below 9.7:1. If you get a big cam you need better exhaust. I did it but it hurt ($1700). If you want to keep that exhaust out of the equation get the max marine roller cam that Comp Cams offers. XM270HR.
Have your builder open the ring gaps to a marine distance. Roller rockers are about 10 or 15 HP, if you go that way Scorpion is the best buy in a US brand. Roller lifters go with the cam I mentioned, but you can do flat lifters too, there's a different listing from Comp for that. I'm a Comp fan, they list recommended parts with each cam.
I also like beehive springs, less force and weight in the valve train. I did Comp there too.
If you go roller cam and want a nice stable lift maybe go for short travel lifters, I did. They can't pump up. Well not as much and not as likely. If you do lift greater than .45" the Vortec heads need some guide clearance. That can be done at home or at the machinist. There are also lots of aftermarket Vortec chamber heads that already have the extra lift and springs in them.
Watch out, lots of possibilities!
I spent this past winter staring at tech sheet and catalogs. Then clearanced and assembled in the spring. Too much work, but I wanted to learn how. And remarkably, it runs.

Back to the original idea...even by itself the cam will give you fuel economy and nice midrange punch.