Help with my 83

My boat, 83 ski naq.. 351 PCM, is having trouble starting when I put it into the water. On land connected to the hose from the house; boat starts ok. I go to the lake and back the boat into the water won’t start… If I pull the boat out of the lake and start it on the trailer then back it into the water no problem all day long even if I stop the boat. I have ruled out the boat ramp angle as the problem because I just pill the boat out of the waster ad it starts even on the ramp at the same angle. A few more thing I have ruled out the impeller, (new and I tested it.. empties a 5 gal bucket in 20 sec @ 2500 RPM), Has any one else had this problem????? I can only hypnotizes that resistance has built up in the wiring of the boat and added presser of the impeller trying to suck up a 1” column water

I wanted to also add, I suggested to some one on the forum about bypassing and cutting the wires to the safety nub inside the tranny. I did this on my boat but and it was successful fix. But I did later repair the nub for safety reasons.. This would be a good test to see it fixed the problem. And my not ruin your day on the lake.. I was yelled at by another form member for suggesting this procedure and my spelling. I had replied from my I phone and I have trouble with that dam I phone keyboard. Sorry for the spelling and misunderstanding.

Thanks Rob

Policerob,
This was the first recommendation made when you first posted the problem:
"start at the tank checking the pick up and the anti siphon valve. If OK then check the hose forward to the pump. Then check the pump with a pressure gauge - It may be getting to the point that it needs replacing." Did you do the checks? In this thread, your first thread on starting problem there are also a couple other ideas for you to check.   I don't know what you are doing with the water pump impeller. That really wouldn't have anything to do with a starting issue.

I was the one who commented on your spelling. I never knew it was such a problem using a expensive iphone as sole access to the internet. I see that you are still using it!

I was also the one who commented on you bypassing a safety device. I'm glad to hear that you went back and made the proper repair. What was upsetting is that you made the recommendation as a repair to another member. That other member may have no idea what the purpose of a NSS is. He may bypass it per you "idea" of a repair and then seriously injure someone by starting the boat in gear.