Jonny 70 lifting under load

[Grounded]

I had the chance to go out in mate's boat today, to cross the Manukau bar. He has a Fyran 540 with a Johnson 70 (2000), electric T&T. The problem was the motor had a tendency to lift when driving hard through heavy seas, quite disconcerting having to throttle back just when you need maximum power at your back. He has checked the oil level and that seems fine, but there doesn't seem to be enough pressure to hold the engine down against a lot of water.<br />Can anyone help please?<br />My thanks<br />Chris

 

[OBJ]

Re: Jonny 70 lifting under load

Hey Grounded.....it's been my experience that with TNT when underway, the power of the engine would keep the engine down and not let it lift up. (Hope I said that in a way that's understandable.) Saying it another way, if the seals and all are good in the TNT unit and the fluid level is OK, the only thing that would cause the engine to raise while underway is the TNT motor kicking on. Have you tried disconnecting the TNT motor to see if there is a possibility of a short somewhere causing the TNT motor to run without hitting the TNT switch? May be something to try.

 

[Dhadley]

Re: Jonny 70 lifting under load

The motors will have a tendency to "trail out" if you chop the throttle when running at or near wide open.<br /><br />Thats the reason we put bungie cords on the motors on Offshore Race boats. Thats to keep the motor tight aginst the trim rams in that situation so it wont slam back down on the rams.<br /><br />While its possible, its hard to imagine that situation with your motor. I would look at the impact valve in the TNT unit to make sure its still operating properly. Your service manual will take you through the steps.<br /><br />Good luck!

 

[Grounded]

Re: Jonny 70 lifting under load

Thanks for these thoughts, chaps, I will pass them on to my mate. Are there any other suggestions out there, as I am sure the T&T motor was not kicking in.<br />Ta