[bushead]

1st launch
Boat behaved well until entering lock cut out as put in gear all dash electrics lost
Found loose connection at fuse board, main power supply to dash. Tightened connector.
At temperature slight water ingress from launch

2nd outing
Fine in marina and at low speed,
Cut out as increased speed in open water. Replaced connector at fuse board, blown fuse couldn't fix towed in. At temperature water from washing boat ?
Replaced fuse board signs of corrosion and melting at fuse. Cleaned all earth connections and checked all connections and plugs. Located pcv valve in rocker cover

3rd outing river test
Electrics behaved but after pushing the boat hard noticed oil in the bilge found oil was coming out of the dipstick, discovered pcv valve was upside down changed over and seems to be working correctly. Continued test after cleaning bilge. Water in engine bay and at temperature boat cut out when in creasing speed though turns. Blown fuse Changed and all ok. Noticed that kill switch had stopped working. Found burnt and melted wires from kill switch removed and replaced. Also found bad connection to stereo. Not been able to identify yet.
When reconnecting kill switch boat ran rough and lumpy with correct connection but smooth and sweet on opposite connection and Kill switch worked.

4th test
Boat didn't want to start and smelt hot/burning once it had. Was at Low temperature and wet. Missed and ran rough under load tried changing kill switch wires but same results both ways round, also stereo was going on and off boat cut out blown fuse couldn't change towed in again

Today
Boat took new fuse and started 1st time, ran well at berth tested kill switch wires boat ran the same with kill switch bypassed and wired either way. Low temperature and bone dry. Engine has developed nasty sounding rattle at high revs. Think bad connection on stereo was coming from fused ignition wire bypassed and seems to have constant connection.

Please help if you can

[Motoxxx43]

You seem to be headed down the right path in terms of electrical issue. My opinion for what its worth: if you are blowing fuses and there are known compromised wires you have to get on that stuff. I'm not going to doom an gloom you over it but that's pretty hazardous not only as a possibly fire source but sounds like the kill switch wasn't working. That's not good.

I'd trace those wires down and get them replaced or fixed before another day on the lake