I put in lithium batteries in my z8 and lost 12 mph

[Ronc4773]

I have a z8 with 225 Merc. I put in four lithium batteries and lost 12 mph. I can run 2 days with no charge and have livescope and garmin force. I dropped down from a 25 four blade to a 24 four blade (fury), went to 3” PAD TO PROP, 91 octane and no tackle up front to gain 10 mph back

 

[cceguy]

12 mph seems to be a lot to lose with a 225 with the changes as described. Did you add the 4 batteries, or did you replace batteries? If you replaced, how many and what type were they? I don't think the part about running 2 days with livescope and garmin has any relevance to the speed drop. This is open to debate, but I doubt if 91 octane in Iowa helps - 87 might be better. If you can, it's usually better to change 1 thing at a time to see what helps. Probably not, but maybe you gained 14 mph with the prop change, and the 3" change lost 4 mph.

 

[Gr8steven]

Perhaps I am misunderstanding... but you added 200 pounds of additional batteries and want to know why you lost mph? Umm does your boat go slower with 3 people versus 2 people? Just saying you know the answer...

 

[Kirby Wilson]

The change in props and the motor height is where you lost the speed. As far as 91 nonethanol octane verses 87 octane there will be little difference in performance. The gas needs to be nonethanol due to the increase of ethanol from 10% to 15% would be the concern now on boat motors.