I am buying a 340 Vyper with 710 hours, runs great, but I am sure it is time for something to be done to the engines to prolong their life. Is it worth doing a top end refresh, about how much would it cost per motor, and what exactly does it include? Any help would be appreciated! Thank you in advance.

With 710hrs, its a crap shoot. I would plan on valve jobs and head gaskets soon.

I would think its gonna cost about $3K per engine to properly refit and refresh the heads per engine both labor, parts and machining. The other real question is that at 710 hours a good compression test and leakdown test may show that the blocks need refreshing also which is gonna cost a fair amount more. Plan for the Worst - Hope for the Best!

Best Regards,
Ray @ Raylar

Labor will be the most costly part. Do you want to drop off your boat and pick it up when done? If so, that will cost 3x as much as if you tear the heads off yourself.

If it works just run it til something breaks then fix it..

I would do a leak down test, that will tell you enough right there what kind of shape their in and tell you where you need to spend your money.