Blessing in disguise

[barnyard]

Bought a engine to relpace in my 23' larson 5.0 sterndrive wound up to be a 5.7 w/ vortec heads, which I like. have a few questions on rebuild
Do i have to change any gearing in outdrive or change prop
Pistons(dished) are later w/ metric rings, can I use earlier pistons w/ fractional rings
Searched" valve guide seals" ,many , many suggestions. Whats best
I know pistons are directional are rods also
Should I install new head bolts
any other tips appreciated
Thanks

 

[Scott06]

You may have to step up in Prop pitch I’d run it and see. I swapped a 4.3 for a 5.0 and kept the steeper 6 cyl drive ratio went from 19” to 21” pitch and it works perfectly
for the valve seal and piston and ring questions I’d talk with your machinist who will be doing the work on this.
new head bolts are better but I’ve done plenty of rebuild and reused head bolts no issue

 

[QBhoy]

Suppose it depends what 5.0 you had. But usually get away with a couple of inches in pitch change.

 

[kvkon]

Bought a engine to relpace in my 23' larson 5.0 sterndrive wound up to be a 5.7 w/ vortec heads, which I like. have a few questions on rebuild
Do i have to change any gearing in outdrive or change prop
Pistons(dished) are later w/ metric rings, can I use earlier pistons w/ fractional rings
Searched" valve guide seals" ,many , many suggestions. Whats best
I know pistons are directional are rods also
Should I install new head bolts
any other tips appreciated
Thanks

You don't "have to" change the prop but you should have enough HP to over rev the engine if you go WOT. You'll have HP that you can't use if you don't change to higher pitch. As long as the dish volume is correct and you don't get the compression ratio messed up the pistons will be fine. What cam shaft are you using? A truck shaft will work however I've measured and found that the Mercruiser cam is sometimes a little more aggressive on lift. Didn't check timing or duration. Standard car lump stick is no bueno.