1990 Johnson 100GT WOT rpm

[Strawn M]

I am looking for the proper RPM at WOT for a 1990 Johnson GT100. I understand from reading that this is basically a 115 which was labeled at a 100 to account for measuring output at the prop rather than the powerhead. I am wanting to change props as the boat has a composite prop on it now which I don't care for. The boat is a Sea Nymph 195 GLS. Current pitch is equivalent to a 17p. I know that asking what pitch to use is a variable answer question so lets start with the recommended RPM at WOT and I will work on this issue.

 

[emdsapmgr]

Re: 1990 Johnson 100GT WOT rpm

The factory states that the engine's normal operating range is between 4500 and 5500 rpm's. Current thinking is that you should prop it to run at the upper end of that range, or 5500. If you run it at 5000, that's considered "lugging" the engine. Once you get a prop that is pitched close to the ideal rpms, a change to a prop of a higher/lower pitch should make about a 300 rpm difference. (I would not worry if the ideal prop lets it run up to 5600.)

 

[Strawn M]

Re: 1990 Johnson 100GT WOT rpm

Thank you for that information. Time to start playing the prop swap game.