Mercury 60/40 4 Stroke 4800 RPM WOT right?

[JL8Jeff]

Just for reference, I have a Lowe 1652 jet tunnel and with my mid 90's 60/45 Mercury 2 stroke I was getting around 28 mph upstream. I'm not sure what the rpm was or if my linkage/timing is correct at WOT because the linkage was broken when I got the motor. I don't normally run close to WOT but I found a small GPS so I did a test. The batteries died before I could get a downstream speed check.

 

[LarryMc]

Sounds about right. I was getting about the same speed with my 2005 Merc 60/40 2 stroke. With the 4 stroke 60/40 I'm lucky to get 26 mph upstream, usually it's around 25.

 

[handyandy]

MrTotty I'll get you a new impeller to send back to them to make merc happy if you'll hold on to that old style for me.

 

[JoshKeller]

Sounds about right. I was getting about the same speed with my 2005 Merc 60/40 2 stroke. With the 4 stroke 60/40 I'm lucky to get 26 mph upstream, usually it's around 25.

what is the weight difference between the 2 stroke and 4 stroke? that may be some of your speed missing.

 

[LarryMc]

According to Mercury, the 4 stroke dry weight is 267 lbs. The 2 stroke weighs 233 lbs. Not enough weight difference to make that much difference in the speed. The 4 stroke motor is just not strong enough to run the standard 6 7/8" impeller at 5200 rpm which is what I got with the 2 stroke. Mercury had to cut the trailing edge of the impeller back in order to get the motor to rev up to 5200 rpm. I tried running my old impeller in the 4 stroke and it would only get 4900 rpm. The hole shot was a little better, but max speed was only around 24 mph in still water.