Hidden leak some where
 

Hey guys i finally got my 77 Sceptre running . Problem is on the starboard side in the bilge area theres a steady flow of water coming in when i go up on plane . Seacock is closed . There are high speed seacock pickups on the bottom of the port and starboard sides to . But I got under the boat and blasted water through to see if that was it ( basically knowing it was a shot in the dark ) . I inspected the entire bottom of the boat for any cracks or holes ...nothing . Any ideas . Ive put 5 months into her . Id hate to have to sell it over a "mystery " leak.

I'll take a shot at it. Check your through-the-floor garboard drain tube to see if it is cracked. When you get on plane, the stern goes lower and water is coming through ? Its the only thing I can think of.

I/O or OB?
pic?

i had a similar issue when i had the 74 sceptre, i took one side of a motor ear muff hooked up to the hose and put it over each deck drain thru from the underside of the boat... and sure enough one side allowed water entry. i ended up re doing them with a heavier duty compression fitting. problem solved.

Well I found I have a rotten transom . I’ll start there

In that case make sure you replace the wooden blocks around the scupper holes while you are at it - mine leaked pretty bad and I also had corrosion holes through the original I/O transom housing and the exhaust Y pipe pretty much fell off while I was removing it. I didn't know it was that bad when I started, but I found out that everything in the stern was basically toast - even the U bolts...

Second the comment on the I/O aluminum exhaust pipe . Im no i/o expert but when i was removing twin engines from current project, both were corroded through with holes below the rubber coupling hose. Holes were high enough that don't think they would have leaked until cooling water was flowing through.

Rotten transom and stringer

Rotton stringer, '77 does not have wood stringers :confused:
The old battery box platforms were glass over wood. Is that what your photo shows ?

my bad brother . yes . Ive almost got her prepped for the new transom