5.0 to 5.7 swap

[05rinkerclay]

I have a 2005 Rinker Captiva with a 5.0 MPI. Puts me at 260 hp...at sea level. I bought it used last summer from a guy in Florida, moved it up to Utah, and the altitude change has killed my hole shot. It just has no power. I repropped from the 21p 5 blade to a 19p, which helped a bit, but not enough.

I'm thinking a good winter project is to swap in a 5.7. I have access to a 5.7 vortec tbi truck engine. From what I've read, I can take all the externals from the 5.0 and bolt onto the 5.7 longblock, and with the MPI intake from the 5.0, I only need to get the ecm remapped? I have an Alpha I lower, so I don't want to go too much over 300 hp, but with the power I'm seeing due to altitude, it feels like I've got a long way to go.

Anyone see issues with this?

As I do a full rebuild on the 5.7 longblock, any mods I should make while I'm in there?

Any help is appreciated!

 

[Scott Danforth]

are you still at a 5-blade? I would try a 17P 3-blade 5-blade way too agressive, even at sealevel. depending where in utah you are, your dealing with a 15-18% reduction in power from the altitude.

build a stroker if you digging into the longblock. other than that, change from the generic flat top pistons to a 12cc or 18cc with the inverted vortec dish, set at zero deck and use a 0.041" head gasket. make sure your core plugs are brass.

 

[Fun Times]

What altitude do you run at? Lake Powell? What gear ratio & model is your stern drive? Also boat size is?

The newer modeled 5.0 MPI 260 HP engine really is a good pretty good engine that does an overall descent job nowadays. In this case you may not gain much overall performance going up to an older model 5.7. Maybe 10 - 20 more H.P. (< Some 5.7 models were in-between the 250 - 280 H.P range)

Depending on the amount of money you may have to put into the entire engine upgrade package, That little power increase may not yield you the same possible performance should you go a different route and change the gear ratio inside the upper driveshaft housing for higher altitudes that's typically recommended by marine manufacturers such as Mercruiser.

Again, depending on the cost you're looking at, If you happen to have an Alpha stern drive, one possible lower cost alternative could be to invest in a new complete SEI upper stern drive housing with a gear ratio for higher altitude vs having your original upper gears switched out.

A new upper from SEI could be around the same cost to having someone switch out the gears. < Then you'd be able to keep the original upper housing should you ever resell the boat to someone down the hill or sell the original housing to recoup your losses.

If interested at all, First here's a gear ratio guide for high elevations,
http://www.boatfix.com/merc/Bullet/Gas/index97.pdf
http://www.sterndrive.cc/Mercruiser-...pper-Only.html

Now if you have a Bravo drive then the SEI idea won't work as they don't offer an upper driveshaft unit.

An ECM remapping can be in the $500.00 range at whipple superchargers marine. https://whipplesuperchargers.com/ind...ategory_id=172

^ Just something different to consider is all....Good luck.

Full: 3,700 ft (1,128 m) Current (July 29, 2015): 3,612.99 ft (1,101 m)

 

[thumpar]

I was thinking ratio also. What is the current ratio?

 

[bruceb58]

If he is swinging a 19" right now and its not quite enough with his 5.0, changing to the 5.7 will probably allow him to use that prop so no gear changes would be necessary. Even if he had to drop to a 17", no gear ratio changes should be necessary.

 

[thumpar]

If he is swinging a 19" right now and its not quite enough with his 5.0, changing to the 5.7 will probably allow him to use that prop so no gear changes would be necessary. Even if he had to drop to a 17", no gear ratio changes should be necessary.

I was not suggesting a gear change but wondering what it is. Some of the 5.0l came with 1.5:1 (or there abouts) or 1.62:1. There are some 5.7l that came with the 1.62:1 for high altitude. It was only to gain more info.

 

[Bondo]

are you still at a 5-blade? I would try a 17P 3-blade 5-blade way too agressive, even at sealevel. depending where in utah you are, your dealing with a 15-18% reduction in power from the altitude.

build a stroker if you digging into the longblock. other than that, change from the generic flat top pistons to a 12cc or 18cc with the inverted vortec dish, set at zero deck and use a 0.041" head gasket. make sure your core plugs are brass.

Ayuh,.... Recipe for Success right there,.... drop a Edlebrock 1409 on it, 'n go Boatin',....

 

[05rinkerclay]

We are at 4500 ft altitude. The prop is a 19 p 5 blade stainless steel. The lower unit is an Alpha I gen 2 1.62 ratio. I'm not wanting to stroke the engine or modify to that degree, but wanting see how much is involved in making this a 300 horse 5.7 MPI. I think swapping the long blocks and remapping will work, but don't want to start down that path and realize I missed something big!

 

[bruceb58]

Ayuh,.... Recipe for Success right there,.... drop a Edlebrock 1409 on it, 'n go Boatin',....

Not sure I would switch from his current MPI to a carb.

 

[Scott Danforth]

We are at 4500 ft altitude. The prop is a 19 p 5 blade stainless steel. The lower unit is an Alpha I gen 2 1.62 ratio. I'm not wanting to stroke the engine or modify to that degree, but wanting see how much is involved in making this a 300 horse 5.7 MPI. I think swapping the long blocks and remapping will work, but don't want to start down that path and realize I missed something big!

I would back off the # of blades. your 19P 5-blade acts much like a 21P 3-blade. I would back off to a 19Px 15 3-blade Solas, or even a 17P x 15 4-blade. and your existing motor will respond.