80’s Mercury Black Max 150 XR2 and Battery Type

[JohnnyG]

I have a 1989 Norris Craft with a late 80’s Mercury Black Max 150 XR2. It’s in the shop right now getting some maintenance. My brother was checking on the boat today and the mechanic told him that the manual for that engine called for a lead acid battery and I’m using an Optima AGM battery. Can me using an AGM instead of a lead acid battery hurt my motor in any way? I have 2 Helix 9’s, led lights, bilge, heading sensor, Ethernet switch, and the other minor boat electronics running off it. I have Odyssey’s running my Ultrex. Thanks.

 

[hoop235]

The AGM battery will work just fine as long as it has enough cranking amps it needs to start the motor.
AGM's are great batteries and the XR2 will never know the difference. Lol!
BTW: That's a great motor and loves to turn RPM's so try to get it propped for 5800 - 6000 RPM's on top end and keep a fresh water pump in it.

 

[silvertalon]

Back when those service manuals were written, AGM batteries were not yet invented.

 

[JohnnyG]

Cool. Thanks guys.

 

[JohnnyG]

hoop235 - 2/21/2019 9:15 AM

The AGM battery will work just fine as long as it has enough cranking amps it needs to start the motor.
AGM's are great batteries and the XR2 will never know the difference. Lol!
BTW: That's a great motor and loves to turn RPM's so try to get it propped for 5800 - 6000 RPM's on top end and keep a fresh water pump in it.

I don’t know much about props. Me and my brother are both 6’ 285lb, plus our tackle/equipment. I can usually get the rpms to only 5000. What do you think would be a good prop and pitch for my boat? I’m basically more interested in fuel economy and keeping the engine in a healthy rpm range. Top speed and and spine ripping hole shots are not at the top of my list. My boat’s fuel tank is only 24gallon and the boat is 17.5ft. Thanks.

 

[silvertalon]

On the XR11, any W.O.T. rpm's under 5,500 is considered 'lugging the motor'. If you can only turn 5,000 at W.O.T., drop down in prop pitch- eg; 23" down to a 21" or 19", to get the rpm's up closer to 6K.

 

[hoop235]

JohnnyG - 2/21/2019 4:18 PM

hoop235 - 2/21/2019 9:15 AM

The AGM battery will work just fine as long as it has enough cranking amps it needs to start the motor.
AGM's are great batteries and the XR2 will never know the difference. Lol!
BTW: That's a great motor and loves to turn RPM's so try to get it propped for 5800 - 6000 RPM's on top end and keep a fresh water pump in it.

I don’t know much about props. Me and my brother are both 6’ 285lb, plus our tackle/equipment. I can usually get the rpms to only 5000. What do you think would be a good prop and pitch for my boat? I’m basically more interested in fuel economy and keeping the engine in a healthy rpm range. Top speed and and spine ripping hole shots are not at the top of my list. My boat’s fuel tank is only 24gallon and the boat is 17.5ft. Thanks.

Sounds like you need to look at a different size and/or type of prop for your setup. My suggestion would be to take the boat over to Performance Propeller in Soddy-Daisy and see Tim Hackney or maybe take it to a local marine and let someone look at it to help you with the setup you need. An XR2 on a 17.5ft boat should turn at least 5500 at WOT. Hope this helps!