Here's the deal. The boat is a 22' Schiada with a Powerglide and #4 Speedmaster drive. Barry (Obnoxious001) just rebuild the 468 blower motor. With the powerglide the motor is pushed pretty far forward with about 18" of exhause hose from the tips (Rex mufflers) to the headers. The whole pipe is underwater.
Starts and runs perfect on the trailer. But once the boat is in the water, the starter can't seem to turn the engine fast enough to start up. Seems like it builds too much backpressure with all the water in the exhaust hose. It will crank and crank but won't fire...... but if you pull the boat up the ramp to where the exhaust is above the water line - she fires right up!
Same when floating. Won't fire sitting still but if getting towed it lights up.
Current starter looks like a basic old marine starter.
Separately but related the relay is going bad and needs some help (tapping) when hot.
Batteries are two new Optimas.
So the questions are - would the relay be the culprit?
Do I need a whole new starter?
What models/brands will allow for a high enough crank speed to blow the water out the exhaust and get the engine running?
Sorry for the long thread - just trying to get as many questions answered ahead of time.