I am trying to see how my 260 hp engine is balanced in my boat,I am trying to get a casting year determined,the boat is an 88 but that does not mean it has an 88 block.
I wanted to know if they are externally balanced,anyone know?

The "old" motors were internally balanced,"new" motors were externally balanced. If motor is in the boat use a mirror or something to try to see if you can see a aluminum 1 piece seal adapter at back of oil pan. If you can see aluminum back there near where pan meets block at rear main seal it has 1 piece crank seal which also means it is the new style externally balanced. The new style motors also use a 1 piece pan gasket and always have center bolt valve covers,Smitty

It does have the center bolt valve covers,I will look at the rear main tonight.

If it's a one piece seal block and crank the crank is external balanced in the rear or flywheel and internally balanced in the front or harmonic balancer side you can use the old style damper on the front but the flywheel has to be the correct one . Best of luck.