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  Mercury 125-HP 2-stoke Classic: Maximum Crankcase Speed

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Author Topic:   Mercury 125-HP 2-stoke Classic: Maximum Crankcase Speed
ALAFIARAT posted 08-02-2004 02:16 PM ET (US)   Profile for ALAFIARAT   Send Email to ALAFIARAT  
What is the maximum crankcase speed on a 1996 Mercury 125-HP 2-stroke Classic? I have recently aquired a 1996 model.Thanks, Dave
Bigshot posted 08-02-2004 03:27 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
WOT is 5250 I believe.
ALAFIARAT posted 08-02-2004 03:46 PM ET (US)     Profile for ALAFIARAT  Send Email to ALAFIARAT     
Thanks Big, I am turning about 5000. Do you think I should try a different prop to find the rest of the rpms? Dave
Bigshot posted 08-03-2004 10:45 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
No
BQUICK posted 08-04-2004 04:19 PM ET (US)     Profile for BQUICK  Send Email to BQUICK     
Dave:
If 5000 is lightly loaded I would go down 2 inches in pitch and gain 300-400 rpm.

Bruce

ALAFIARAT posted 08-04-2004 06:02 PM ET (US)     Profile for ALAFIARAT  Send Email to ALAFIARAT     
Thanks Nick and Bruce. By lightly loaded do you mean boat weight? The boat weight is about 1500 lbs. I have trim tabs, also. Dave
jimh posted 08-04-2004 08:23 PM ET (US)     Profile for jimh  Send Email to jimh     
Increasing the engine speed to 5400 would put it above the maximum of 5250--probably not a good idea to run that engine above 5250. The in-line four cylinder without balancing shafts is not a high-rev engine. I am sure you can run that engine at higher speeds, but the very low rating of 5250 tells me there is a good reason not to.
merc125 posted 08-04-2004 08:43 PM ET (US)     Profile for merc125  Send Email to merc125     
Max torque at 4800, leave it were its at. what prop are you running? MartyD
Swellmonster posted 08-04-2004 10:29 PM ET (US)     Profile for Swellmonster  Send Email to Swellmonster     
Lightly loaded is less than a six pack! ;)
ALAFIARAT posted 08-05-2004 07:15 AM ET (US)     Profile for ALAFIARAT  Send Email to ALAFIARAT     
I had to check the prop size while the boat is on the lift. I can find the number 23 for the pitch but may have to remove prop to find the dia. Dave
Richard Quinlivan posted 08-05-2004 10:38 AM ET (US)     Profile for Richard Quinlivan  Send Email to Richard Quinlivan     
I have a 1995 125 Merc. I have run it as high as 5600 for short spurts with no bad results. That being said max HP is supposed to occur at about 5000 rpm. My recomendation would be to prop the boat so that you can get to 5250+ at your lightest total boat weight when the weather is cool so that as you load the boat up with people and equipment and the temperature goes up in the summer causing rpm to decrease the available HP and Torque will be higher. That will give you a stable operating point.Dick

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