We recently purchased an '87 Searay with an OMC 4.3L V6. It ran great the first three times we had it out but on the 4th trip it suddenly went downhill .... It now idles fine and engine revs good when in nuetral, but as soon as it is put in forward or reverse, it sputters a little, and then dies. What's up with that? Can anyone please help me out?