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Challenges upgrading 5.0Gi to a 5.7Gi?

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freezer

New member
I'm very confused and looking for some guidance... I froze and cracked my block and need to replace it. First, my specs, then my source of confusion.... specs. Boat Type: 1999 Cobalt 190; Engine Type: Volvo Penta 5.0GI PWTR - 4110182291 / 3868945 (145 hours on original 1999 5.0L/GM 305 engine); Transom: Volvo Penta TSK SX-M - 4111605798 / 3868844; Drive: SX-M 1.6 - 41120622380 / 3868891. Most everyone I talked to has suggested taking the opportunity to upgrade to a 5.7L/350, and have suggested that my "stuff" will bolt right on a 350 long block... I would like more hp, top end and better fuel economy that it would provide, but this seems to be where the concensus ends.... Someone said I might have to replace my intake manifold (others said no). Someone said I might have a problem with my fuel injection system on a 5.7L (others have said no). Someone (I think it was a FirstMate, Gator Engine or Rebuilt.com rep) said I might have to replace my computer as Volvo Penta computers can't be reprogramed for the bigger blocks like Merc's can (others have said no problem), someone suggested saving a lot of money buy buying a low milage used or rebuild 350 truck engine, replacing the cam shaft with my existing and going that route, others have said no spend the extra $ on a rebuilt marine engine.... Just not sure who to believe... Any guidance, insight and advice on the above issues would be very much appreciated...
 
My 2 cents:
If you are only running on Lanier, you can get away with a used truck engine which needs no modification for fresh water use. Just bolt on your bellhousing, coupler and manifolds and go. If you run in salt water you will have to change the (freeze) plugs with brass, put on a marine type circulation pump, and use a cast iron intake manifold.
I don't recommend a truck motor because by the time you get all the grime off, paint it and replace the gaskets, swap parts, blah blah blah, you have spent in labor and time the difference between a used engine and a reconditioned one.
A reconditioned short block 350 is only about 12-1400. In boat dollars that's not much considering an outboard with similar HP is about 20 grand.

You have to look at the big picture. To be honest, a 19 foot Cobalt that's ten years old with a blown engine is not worth much...maybe a thousand bucks to someone who will repair it and flip it. Are you ready to put money into what is more or less a worthless boat? If yes, read on...

If it were me and believe me I have been in a similar pickle enough times (like right now for instance) I would buy a reconditioned 350 short block that is ready to bolt my stuff to and put it back in the boat. You will need new gaskets for the heads intake and exhaust oil pan and water pump. All your 305 stuff will bolt on no problem and you can use the EFI and computer without any problems. If you do not have mcuh experience with marine engines, then by all means pay a marina to do this for you.
Bottom line is that you are not going to get out of this situation without losing a fair amount of skin. My advice is to do it in such a way that the pain is not prolonged.
 
Your boat with a cracked engine block is worth even less to you as it is. Don't fear replacing an engine.
Boats are NOT investments.... they are expenses! We use it UP in the form of enjoyment and pleasure!
Keep the Nah-Sayers at bay! :mad:


Your camshaft and cam followers (assuming roller) are re-useable. No harm in doing this! You can just barely wear out a roller cam/followers..... and in only 145 hours, yours should be just fine!

Steer clear of the truck engine..... it will be equipped with dished pistons, although in your small hull, this is not the issue that it may be for a larger hull.
If you build one, use a Low Compression Quench Effect piston.

The 5.7L, if in the same vintage block, will allow for your goodies to transfer. I doubt that you will have an issue with your FI.


Have you considered a new 5.0L block, new bearings/rings/gaskets, etc?
Mic the pistons.... if good, re-install with new rings......... The only NEW pistons are still in the box, and sitting on some parts house shelf.
Pistons in a SBC have been known to make it to 1,500+ hours!

.
 
Thanks for the advice guys! If I go the rebuilt 5.7L short block route to save money and bolt on my 5.0L heads, manifolds, etc... is there any concerns that you can think of? Any reason to steer away from the 5.7L upgrade and stick with the 5.0L short block?
 
It would not be wise to use the 5.0L cyinder heads unless you chose the correct piston for a 5.7L in order to achieve the correct compression ratio.

Like said, if you build one, you get to choose the piston style.
You can go with a correct marine pistons......... i.e., a reverse dome, low comp Q/E or a "D" dished.... (any of which can give you a Quench Effect combustion chamber)......, and steer clear of the Dog Gone dished pistons!
You'd need to know the combustion chamber size of the 5.0L heads. Then speak with a rep from a piston manufacturer/company, tell him what you are doing, then ask for some suggestions.

There is no reason to steer clear of the 5.7L other than you probably don't need it for a 19 footer.

An even better Bang for the Buck, would be the Duo Prop lower unit if you want more power/speed, IMO.
 
Wondering if anyone can respond to some new information that I received today.... I was just told that the EFI off my 5.0L won't supply enough fuel to a 5.7L with reprograming my ECM. It might run ok for a while, but with the Vortec fuel efficient technology, it will let in more air into combusion but will not supply sufficient fuel, and apparently it will ultimately run much too hot and will burn out the engine/burn up a piston or two... Apparently the ecm computer can be reprogramed by AZ speed & marine if it's a Delphi model, but if it's the V-Tech model, I'd likely have to buy a new computer at a cost of $1000... I'll have to check on which model ECM, but now I have some concerns about upsizing to a 5.7L. Any thoughts????
 
I've decided to buy a new 5.7L long block and get my delphi 16237009 ECM reprogrammed, oh and go with the dual prop! This little 19ft Cobalt should move along pretty well after all this (I hope!). Can anyone suggest a good source to reprogram my Delphi ECM for the 5.7L? Also, I have a least one freeze cracked exhaust manifold. Can I get the other one and elbows tested to make sure they are OK before reinstalling them? Is it something I can do myself?
 
freezer said:
I've decided to buy a new 5.7L long block and get my delphi 16237009 ECM reprogrammed, oh and go with the dual prop! This little 19ft Cobalt should move along pretty well after all this (I hope!). Can anyone suggest a good source to reprogram my Delphi ECM for the 5.7L? Also, I have a least one freeze cracked exhaust manifold. Can I get the other one and elbows tested to make sure they are OK before reinstalling them? Is it something I can do myself?
Click to expand...

I know it has been a while on the thread but did you get the PCM reprogrammed and how was the engine running at high RPM? Who did you use? I have recently swapped a volvo penta 5LGxI that had a cracked block with a 5.7L Mercruiser. The PCM (Delphi) was sent out for reprogramming. The engine seems to misfire or sputter when 4400RPM is reached.
 
mikeinAiken said:
I know it has been a while on the thread but did you get the PCM reprogrammed and how was the engine running at high RPM? Who did you use? I have recently swapped a volvo penta 5LGxI that had a cracked block with a 5.7L Mercruiser. The PCM (Delphi) was sent out for reprogramming. The engine seems to misfire or sputter when 4400RPM is reached.
Click to expand...
Hey indid the swap from 5.0 to 5.7 had my ecm reprogrammed but at 4200 seems to misfire run great other than that any insight? Everything is new
 
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