Johnson 80-85hp owner's.....What speed you getting out of your motor?

BonairII

Commander
Joined
Jun 7, 2011
Messages
2,727
Before I even bother trying to get more speed out of my '67 Johnson 80hp motor, I need to know approx what speed this motor is capable of.

My 15' Glasspar weighs 675lbs, motor 240lbs, gear/fuel/me 310-ish lbs.....and I'm getting a max speed of 33mph w/ stock prop.

If this is normal, I'm fine with it. But if people are getting 40+mph out of similar rigs then I'll do some more tweaking.
 

ADK_Boater

Petty Officer 1st Class
Joined
Jun 29, 2010
Messages
217
Re: Johnson 80-85hp owner's.....What speed you getting out of your motor?

Do you know your WOT rpm's?...if not does it sound like it's 5000 or so?
What size and pitch is your prop? (might want to look into higher degree of pitch if rpm's are good)
How's the hull on your boat?
I have a 75 hp that weighs 234 lbs on a MFG with a deep-V that weighs 900 lbs, and I'm getting 36-38mph, if that helps. I've gotten 35 out of it with three people.
Seems like you should be getting at least 40+.
 

BonairII

Commander
Joined
Jun 7, 2011
Messages
2,727
Re: Johnson 80-85hp owner's.....What speed you getting out of your motor?

I don't have a tach and have no idea what 5000 rpms sound like on an outboard. I'm going to pull each plug wire one at a time just to be absolutely sure all cylinders are still firing.

I'll have my son with me tomorrow, so maybe I can tweak etc while he drives.
 

McGR

Senior Chief Petty Officer
Joined
Jun 19, 2004
Messages
654
Re: Johnson 80-85hp owner's.....What speed you getting out of your motor?

I used to run an 85hp Johnson on a Sea Nymph 17' full console aluminum fishing boat. On one occasion I managed to hit 40mph (GPS) on that rig. It always frustrated me that after hitting 40 it was never able to do it again. The conditions that day for some reason must have been perfect... Day in / day out it used to run 36/37 top speed with a 19" prop.
 

BonairII

Commander
Joined
Jun 7, 2011
Messages
2,727
Re: Johnson 80-85hp owner's.....What speed you getting out of your motor?

Just found the size of one of my extra props 10 1/4 x 10. I'm not sure what prop is on my motor right now.
 

laotou

Seaman
Joined
Jul 8, 2011
Messages
54
Re: Johnson 80-85hp owner's.....What speed you getting out of your motor?

My 16' fiberglass boat is 750 lbs. The 85HP engine weighs 290 lbs. Fuel, batteries and me are 280 lbs. The top speed is 31 mph.
 
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