refitting my 23 foot cobalt. the twin merc 350s are in need of rebuilding. if it were you would you rebuild them or i found these pair on craiglist
copy and paste ....
"Used, pair of GM 350cid, carbureted High Performance motors, rebuilt with super Low Hours, (70)
Chevy Bow-Tie heads, roller rocker arms, Dominator performance intakes with Holley double pumper carburetors.
New center rise Osco exhaust manifolds, spacers and risers, power steering (1 engine). This pair has taken a 5800 lb 26 foot Well-craft 74 mph ! Peak power at 5800 rpm ! These are 400+ H/P motors"

would it be fasle economy to just do a ring and valve job on the existing engines?

your thoughts. thanks, guy is asking 7500 cad

First - Where are you located?
Second - Don't spend big bucks on items off Craig's List, Ebay etc.
Too many horror stores. Too many scams.
Third - Spend big bucks with a well known marine engine shop only.
Too many small shops can't handle the job properly.
Fourth - Rebuild before swapping unless you know the engines you're
getting and the person selling them.

Post this question in the Technical section and give a lot more detail
about your mechanical skills, location, willingness to drive, maximum
budget, and desired HP levels.

k thanks!...
we are located in vancouver canada, planning to make a few trips across to the big island and many day trips to the smaller island chains. even a few runs up the sunshine coast.
getting ready to pull the engines in a few days and was going to start disassembly, inspection and get em ready for the machine shop.
just thought it be easier and faster to buy engines that where all ready built, but now i got to ask myself, why with only 70 hrs is this gentleman selling them? anway.....

Vancouver eh?
Get with Alex Haxby - http://www.haxbyspeed.com/
He can help with the rebuilds or the take outs and any questions you
may have.

I did an HP engine swap 7.4L MPI to 502 MPI since it was easier and
cheaper. However I protected myself from the buyer by having my
mechanic do tests and we used an escrow account to hold the money
until I was given the thumbs up from him. The seller was a good guy.
Nothing wrong with buying good takeouts. The trouble always lies
with an unscrupulous seller.

perfect.... thanks.

Trade em in on a merc reman

They r new motors that r carbed so can't n
Be sold new do to emissions the 357 is nice

http://www.ebay.com/itm/Mercruiser-3...-/120538763556

hum. looks good. gonna check out the guys at hax by speed. not too far away from where im working. ill have a chat with them and see what they can come up with.
or i may tear em down and send the parts to the machinest and bring em back up.