RAM mount question

In have a new Humminbird 899 on the way and am looking at the Ram Mounts for this unit. Ram recommends the 2.25 inch ball size, but the 3.68 inch base will not fit in the area that I need it to mount to. The Ram with the 1.5 inch ball has about a 2.75 inch base and will fit- and is rated for units up to 10 pounds, which is double what the 899 will weigh. Has anyone used a Ram mount with the 1.5 inch ball for this size unit and what is your comment on how well it works? I have a 115 horse motor on an 18 foot Seaark boat so I am normally running 40 mph or less. Thanks

i used 1.5" ball worked good on 898 now i got 999 on it

I got the 899 also and I got the 2.5 and it is rock solid. Maybe the 1.5'' will work OK but I would rather be safe than sorry maybe the 2.5'' is over kill but very happy with it.

Have the 1 1/2" inch system on my 898. rock solid...

http://www.crappie.com/crappie/boat-...95-dc-rigging/

danny