5.7 runs on muffs, not on the water.
 

Wanted to freshen up my runabout heres what I've done. New camshaft, New Edelbrock carb and intake, New mallory distributor and coil. Only thing not marine grade is the cam and it is a very mild street cam. Still running the through hub exhaust. The problem is it runs like a champ in the driveway, back it down the ramp and it is very hard starting and when it does go it wont stay lit. Pull it back up the ramp and it fires right up. Need help please.

could be the angle you are putting it in could be flooding out the carb

Check your float levels.

cam shouldnt matter whether its marine or not. Its probably your floats.

Could it be reversion? Is there a way to see if it is reversion? Like when a head gasket is blown? I went as far a floating the boat before I tried to start it and to no avail. The floats are possible, but I could try it in the water and pull it right back up the ramp and it will fire in a half a revolution

Water from reversion would still be in there when you pull it out, try jacking the front of the trailer up to simulate ramp angle

Lil Red, That is a good tip, That should have dawned on me. I will try it and see what it does. Keep them coming supposed to be taking this boat with me on vacation in a couple weeks.

Went to the lake last night, backed down the ramp but not in the water, wouldnt fire. Pulled up the ramp adjusted floats and tried again, backed in and it fired up. Still seems a bit rich but runs. Still missing a 1k rpm. I am getting closer.

Your on the right track now, float level really wont effect rich or lean, now its a matter of adjusting idle mixture screws and jetting

And adjust the float level when the boat is in the water, I know my boat is very stern heavy and sits low in the water. Level on the trailer is nowhere near how it sits in the water

+1

+2

Going to the lake tonight with a new set of clean plugs, and try her again. Will keep informed.

A friend of mine had the same issue with a SBC..it would start and run good on the hose..back it in the water and nothing..pull it up and it would start..turned out to be the cam..he didnt have thru hull exhaust and wanted it so he added that instead of changing the cam..(per the advice of someone else)..I think they said it had something to do with back pressure????..I'm really not sure..but the thru hull exhaust fixed it..I hope this is some help..