A lower ratio leg with higher pitch prop is better than the reverse
Another example same Formula 27PC
530HP motor using a 1.82 ratio drive would get up but not very well. Switch to 2.00 drive and came up much faster. The lower ratio let the motor spin up into it's max torque area sooner
If the crane scale was accurate then the only thing left is you need more motor. The boat most often came with twin 225 of 260hp motors. Your setup sounds like the Formula 27PC I had with a single 454. The single motor didn't have enough power for the hull. I swapped out the motor a few times...
Back firing through intake is caused by spark happening at wrong time, intake valve not fully closed.
It's suggested to keep a spare cap in the boat and wait for issues to start that are unexplained easy. Swap out and if it's fixed all good, if not dig further
The caps on these motors may last a long time and others have a very short life. You can't look at one and see that it's bad. Search the net and you'll find they go out without warning. Yours may be fine but only one way to find out
If cap is good I would do a compression test
I would suggest taking boat and having it weighted
Boat spec says it's around 6K lb, so with gear and trailer its up around 10K. Wonder if hull is water logged
I had a Merc that feed the water heater from the block drain port going in and the water pump housing on return. I don't have a VP 5.7 cooling system manual so I would guess which ever ports where used for open can also be used for closed unless the outlet went to the exhaust elbows
Which 5.7...
Many are installed this way because the Red wire terminal is not large enough to connect direct to starter post. In Merc documentation it list Red as Bat power unfused and Red/Purple Bat power fused
Check the voltage on the other side of the 50 amp breaker
If it deals with the motor running it stays on the start Bat, as in key switch, gauges, starter, alternator, power trim, etc
If it's for any other stuff, this can go on the house Bat
