72' 85hp Johnson WOT RPM?

[Fishstick1962]

I have a Clymers (I Knooooow!) it is clear as mud about WOT RPM for my engine. Best I can tell it says 4500 is wot. That sounds kinda low to me. One mech told me 5500. What do the pros say? I'm fixing this one up for my dad and after finally getting her to run (runs greeeeat!) I don't want to blow her up now!

 

[red boat]

Re: 72' 85hp Johnson WOT RPM?

5500-6000. prop for 6000

 

[steelespike]

Re: 72' 85hp Johnson WOT RPM?

My intertec manual says it developes its hp at 5,000 rpm.
I would think 5,500 to 6,000 would work.
I'm pretty conservetive I would shoot for 5,500 with your normal load.If I tended to run alone much of the time I might shoot for 6,000 but run her easy when alone.

 

[Fishstick1962]

Re: 72' 85hp Johnson WOT RPM?

Thanks guys, I sure appreciate the help. I'll prop for 6000 empty and alone. That way under load I will probably see closer to 5500.

 

[emdsapmgr]

Re: 72' 85hp Johnson WOT RPM?

The engine was originally rated to operate between 4500 and 5500 rpm. It is rated at 85 hp at 5000. You have a low-ported block and it's design capability will start to run out of breathing capability over 5500 rpm. You will get better engine life by propping it in the 5500-5700 rpm range instead of 6000. That's only one prop size difference.