Mercury 75hp RPM at 5500 ?

 Can anybody assist me with why the max RPM on 75HP mercury 2/stroke is 5250.

I have a Stejcraft 2002 5.25 with 75 outboard.Propped with 13x17P 

RPM at 5500 and 32knots

Does anybody think I need to re pich prop and go up to 19P?

Any suggestions would be fantastic.


Posts: 4561

Date Joined: 01/02/10

 Light load or heavy load?The

Wed, 2016-10-12 09:49

 Light load or heavy load?

The 75's are rated 4750 to 5250 rpm. Funnily enough the 75 is a debated 90 and their rpm is listed as 5000 to 5500. Same motor. 

I wouldn't be too worried. 

____________________________________________________________________________

Does anyone know where the love of god goes, when the waves turn the minutes to hours?

Lukastoy's picture

Posts: 8

Date Joined: 04/10/16

 Thanks DodgyJust myself in

Wed, 2016-10-12 10:09

 Thanks Dodgy

Just myself in boat and 70L of fuel.No additional weight was added at the time.

Ill do another test this weekend when I have a partner and gear on board.

Cold Feet's picture

Posts: 120

Date Joined: 04/08/15

Thats about what to expect..

Wed, 2016-10-12 12:42

 I think...., as I have the 90hp 2 stroke and still strugging to get over 4500rpm on a 5.35 runabout - I have the specs and manual if you like send me a pm with your email and I'll send it over - I assume is a 2000 year model plus?

Dodgy is correct the 75 WOT RPM is 5250 -5500 in the book.. seems your is running pretty well. I max out at 26 knots at 4500rpm, but boat is loaded and fibreglass older model.

I think the thoery is peak fuel economy, cooling and ideal rev range at 5250, so tap off a few knots if you are running a long way, and keep it at the peak 5250rpm for economy... not many places you can hold 32 knots anyway for any long period of time in a 5.25m boat?

____________________________________________________________________________

 Cheers,

Cold Feet 

 

Lukastoy's picture

Posts: 8

Date Joined: 04/10/16

 Cold feethave you looked

Wed, 2016-10-12 16:51

 Cold feet

have you looked into dropping pitch on your prop ?

what prop are you running at the moment ?

 

this could help raise your revs !might get some top speed ?