Best way to cut bigger holes in transom?

[THRILLSEEKER]

I'm switching from 2.5" exhaust tips to 4" tips. whats the best way to cut the existing holes bigger and keep them uniform and on axis? Do they make a hole saw pilot that big??

[Full Force]

Well.... since I am doing the same thing.... I have an idea so far, i am going to mount a piece of wood from the inside through the existing stud holes, that will get me started, once it is started I am sure the hole saw will flollow.. thats the only thing I came up with so far.

[ROGUE]

There was a pretty good thread on this on OSO but it was a long time ago. Not sure if it still is there. It was pretty much what Tim said. Do it from both sides though.

[THRILLSEEKER]

I was thinking of using a 2.5" or 2 9/6" holesaw to cut a "plug", screw a backing board on the inside of the transom, and screwing the plug to the backing board. The plug already has a pilot hole on the proper axis.

..thoughts??

[bajalion]

Put a 2.5 hole saw inside the 4" hole saw. The 2.5 will act as pilot.

Works the same on gauges and exhaust tips......not that I would know.:Wall:

[Bouyhunter]

Put a 2.5 hole saw inside the 4" hole saw. The 2.5 will act as pilot.

Works the same on gauges and exhaust tips......not that I would know.:Wall:

EXACTLY!!!

Make sure you have a good arbor that will accept the "stacked" hole saw combo.
I used to use this trick all the time back in my carpenter days.
Just need to get the larger hole started (through the Glass) then remove the smaller hole saw, and finish with just the larger one.
Piece of pie, easy as cake.

[OUTDRIVE MAN]

Well.... since I am doing the same thing.... I have an idea so far, i am going to mount a piece of wood from the inside through the existing stud holes, that will get me started, once it is started I am sure the hole saw will flollow.. thats the only thing I came up with so far.

This is how we do it at work. id like to see if bobs way is easier though, i think ill have to ask the guys to try it out.

[Full Force]

Put a 2.5 hole saw inside the 4" hole saw. The 2.5 will act as pilot.

Works the same on gauges and exhaust tips......not that I would know.:Wall:

DING!!! we have a winner!! I like that idea!! I never thought of that one!

[ROGUE]

Dont buy the 4-1/8 hole saw. You can use mine. It might even be 4-1/4. I have to look when I get home from NC.

[THRILLSEEKER]

Thanks Tom, Ive got a 4.25 but I think its going to be a little on the large side. I think 4 1/8th is the ticket. Looking at my lennox 4.25 right now, theres only about 1 full thread of the arbor base protruding thru the inside of the blade, not so sure that there is enough there to thread the 2.5 on top of the 4 1/8th.

[ROGUE]

Thanks Tom, Ive got a 4.25 but I think its going to be a little on the large side. I think 4 1/8th is the ticket. Looking at my lennox 4.25 right now, theres only about 1 full thread of the arbor base protruding thru the inside of the blade, not so sure that there is enough there to thread the 2.5 on top of the 4 1/8th.

Yea, Ive got a real good one and there isnt enough to thread on a second. I think youre plan will work well. I will be home thursday and can check my hole saw but I know it is the minimum so it must be 4-1/8. A large rotary rasp works well for minor adjustments. Make sure you west system the hole good before installing the tips.

[ROGUE]

I will add one more thing. Please dont cut the holes until the enignes are in and properly aligned. I had a hell of a time making angled shims for the formula with dry pipes to try and hit the holes because the original holes were off. And please dont think that you can make it work with the rubber hoses because they will burn where the bend is. BTDT. You can buy these cheap laser sighters now for all kinds of saws that you can attach to the elbow and see where the hole should be. If it hits right on, great. But if it doesnt, its a lot easier to move the hole before you make it bigger than after.

Just my $.02.

[Full Force]

I was going to wait until engines are in since I am using a totally different exhaust, thanks for the tips Tom!