I am removing the bottom paint and talked to a few marinas that blast it off with walnut shells. anybody have experience with this? Any tips...I have 40/100 media to use. This is on my cruiser and I will repaint with Interlux.

Walnut shells can do a good job, however - removal is not always a sure thing, adhesion, intercoat adhesion , thickness of existing paint, type of fiberglass, gel coat thickness and health of the OEM gel coat are all factors. What works for one does not always work for the next. As a rule of thumb start with the fine/small grit size with moderate pressure 5-75 psi - if the project is going ok increase the pressure up to 120 psi - if work is still going well increase grit size and drop pressure - start all over again -

You will likely rupture blisters, spald off some gel coat and in some instance not be able to effectively remove paint, drips sags etc.. stop and sand or grind these areas -

Protect the blaster from resulting dust using air feed helmet & tyvek suit, walnut shells become a huge mess when they blow around and get wet - do this in a freinds yard not in your own -

Air required 5/16" nozzle = 150 cfm @ 120 psi
3/8" nozzle = 200 cfm @ 120 psi

Thanks.

soda blasting is the way to go.

I agree. Just watched a professional take bottom paint off a boat with baking soda. It is the only way to go.......

Don

Lots of different type of blast media can be used, includeing baking soda - fact is each bottom, type of coating and coating thickness is different - no way a single method will work on all paints - each have advatages and draw backs - CO2 blasting ( Blasting with dry ice) may be the best/simplest method, no clean up because the ice evaporates realative soft media etc.... the cost is 5X however of a conventional blast -
If your doing this yourself - use local materials and local equipment and work slow and steady - If your going to hire a professional, explain your expectations and paramaters and allow them to select the method/media used. When you mow your lawn you have the edger, weed eater, push mower and big tractor - Don't limit yourself and believe that one method or grit type will get you where you want to end up -

Good luck - and why are you still screwing with this??? - the sun is out you should be in the water -

Thanks James, Yes i should be on the water. Unfortunately work has kept me from getting the boat ready. I leave for houston today for a week and I hope to get it finished next weekend. The slip is waiting for me at Grand Lake in Oklahoma.