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I'll run the risk of 'troublemaking' by making two posts on the one thread and point out air (oxygen) doesn't come into it. In chemistry terms oxidisation is the loss of electrons. With galvanic corrosion or in a galvanic cell one metal robs the other metal of electrons. it's also called a Redox reaction (short for reduction/ oxidisation).

I'll run the risk of 'troublemaking' and point out that it's galvanic corrosion you have to worry about in this instance. Ie when two different metals come into contact the less noble or more reactive one will corrode. Unfortunately it's aluminium that will be the metal to corrode in most cases. You don't need any external current for galvanic corrosion to occur, but the metals need to be exposed to the same conductive solution such as seawater.

I did just point that out in a post.

The fact is that explosions as I have described, though unlikely, have have happened. On top of that accidents from angle grinders kicking back or disks exploding when cutting metal are not infrequent. Offiicial safety guidlines for angle gringers usually state that alternative (ie safer methods) should be considered first.

There is another way it can explode called a thermite reaction which can occur when iron oxide is mixed with powdered aluminium. It is therefore not a good idea to use a cutting wheel or a grinding wheel that has been used on rusty steel susequently on aluminium. PS: You don't seem to have considered that though you are using a safe cutting method someone else might try to do the same project after reading this thread and would have done it in an unsafe way if i had not highlighted the pitfalls.

It's happened, I can give references if you are really interested.

I did say specialised equipment - most people dont have a mig or tig welder lying around. With angle grinders but it is not unheard of for people to notice it's not cutting so they will press harder, the heat generated can be enough to melt the aluminium hence the clogging. Explosions are rare but not unheard of (aluminium power is a common ingredient in explosives) . Also people have used saw type blades in angle grinders and they have shattered and angle grinders are not completely shielded. Fiber reinforced grinder blades may not shatter but the grinder can be prone to kicking back if the disc gets caught and lead to injuries.

Apart from being a qualified chemist it is fairly common knowledge what I have said on these topics.

I wasn't suggested he weld the floor, just asking. If i was doing the job on my boat I wouldn't use aluminium in any case - I'd go for plywood and seal it well with epoxy.

Are you going to weld the aluminium floor in? That will require special skills and equipment. Also you will need a safe way of cutting the aluminium. Angle grinders are too fast and the disc can jam and shatter and injure you. There is also an explosion hazard from the fine aluminium particles generated. Plywood should be long lasting if you seal both sides and edges and holes you have drilled with epoxy resin (it's very good at waterproofing) and easier to work with.

Some people have made their own using electric linear actuators from trim tab units.

I have had WD40 it eat away the rubber or plastic (I'm not sure of the composition) plug on my echo sounder, so that's why I'm wary of spraying it all over my motor. I think there are better products to use.

It might be more cost effective to sell the motor and buy a new one (with trim and tilt).

With a short rod you will be able to exert more pressure on the fish (less leverage disadvantage) and so pul them away from the pylons.

There are rubber hoses carrying the cooling water and these won't be the same composition as fuel hoses. Then there are plastic parts of various composition, seal and gaskets as well as greased moving parts which may not react well with WD-40.