top rpm on 78 merc 1400 (140)

[mirf1200]

Just purchased a 78 glastron 17.5 ft fish/ski. The motor (78 merc 140) runs great and compression is 130 on all six cyl, Im seeing 4300 rpm at WOT and maybe 30 out of the boat (guess) is this what I should expect?

 

[what200]

Re: top rpm on 78 merc 1400 (140)

If 4300 is your WOT rpm, you are likely damaging the motor. You need a lower pitch or the motor is not running correctly.<br /><br />Check compression.<br />Prop this motor for 5700-6000 with a light load in the boat. Run 93 octane and set timing to 20* BTDC max.<br /><br />BTW- this motor is identical to the 77' 1500.