Any Yanmars out there?

[Skookster]

Hoping you're all weathering the virus storm, maybe with 5:00 quarantinis!
The PO repowered Skookum with a Yanmar 4JH3E. It has been a great engine with zero problems, a good thing since access is tight. This spring's Balmar alternator upgrade project is gonna start with pulling the harmonic balancer to install the Balmar serpentine belt kit. There's maybe 3/8 inch clearance at the bottom of the harmonic balancer to the glassed crossbeam between the fuel tank and the engine, and no more than 6 inches to the fuel tank. Makes most pullers impossible to get in place. It is looking like I'll have to cut away some of that crossbeam to align the puller forcing screw and pull the balancer off.
Anybody else dealt with this and have words of wisdom?

Update: This was tough boat yoga but worth it. Access sucks! Got just enough clearance to get the balancer off with a star-type puller if I didnt use the centering point on the forcing screw. So task one solved. But getting the new pulley back on over the old wasn't gonna happen without chopping away on that "beam". Photos show how much to cut. Not so bad. Not really much of a crossbeam, it was a hollow inverted U. New alternator pumps out tons more amps. Two thumbs up--Balmar makes a great kit.

[SVJourney]

You will need an impact gun to get the bolt out of the balancer without the crank turning.  I tried on the 'Beke to get it out and totally failed without pulling the engine.  Lots of torque. 
I would remove the mount bolts and slide the engine forward before I cut a structural beam, but I understand that it will be a horrendous job.

[Skookster]

Thank you! I'm definitely concerned about that beam. Hoping I can nibble away just enough with an oscillating multitool (Best Tool Ever!) and repair/reinforce afterwards.

It seems that I don't need to undo the large center bolt on the crankshaft pulley because that pulley won't be removed. It is covered by a slip-on pulley in the Balmar kit, then the balancer goes over both. But even the six perimeter bolts that hold the balancer on may be seized, so a great point to be wary of. Now even more concerned this will end badly! I probably oughta nail all the bolts that have to come out with a shot of pb blaster the week before, huh?