My chevy 350 boat is back fireing?

Question

I have a 1983 Sun Runner boat with a in board chevy 350 out board 800 omc. I can run it off the hose and it doesnt back fire in nutural, nor in drive when I rev it up. the last time I tryed to take the boat out it idled just fine at the dock, went threw the no wake zone and when I got out and gave it some gas it peaked at 2 grand and started back firing out of the carb so I let off and tryed bring it back up same thing, so I turned back around and the boat died on me right as I got back to the dock . Also today I put it on the hose adjusted the electronic choke( some one told me that it was choking out on me) and let it run for a wile and noticed that the oil pressure gauge would drop down to about 5 or 10 and wouldn't come back up when i let off the throttle. does that mean i need a new oil pump or what. What do I need to do im by no means a mechanic but I don't want to get riped off by one so I want to know exactly what to tell them to fix so I can get back in the water.

Answer 1

Sounds like you have a sick chevy 'mouse' motor.  If this is in an 83 boat, it may be that this engine has never been rebuilt.  The oil pressure is read off of the cam bearing, however, it is indicative of an overall high wear problem.  With oil pressure that low, i would rec. a rebuild, or install a rebuilt engine. While there are mechanics who abuse these situations, find a reputable shop, and get their opinion.  However, the back-fire is most likely not a high wear issue, it is most likely either carb or electric in origen.  I would hesitate to spend too much time and money finding the ignition or fuel problem, if you are indeed going to rebuild the engine.  If you just want it quick and dirty, replace the plugs, rebuild the carb, and do an igniftion rebuild.  Good luck, and be safe.

Answer 2

Sounds like something to do with your cam and cam bearings with the loss of oil pressure Chevy. engines read their oil pressure off the cam bearings and the back firing could be due to missed timing because of cam and or cam bearing wear. That would be the first thing I checked if it was mine anyway. Built a lot of small block Chevy's only one marine engine their built a little stronger usually four bolt main-ed or cross bolted, but otherwise the same as automotive engine.