OMC block/powerhead ID

[76Stingray]

I am trying to ID a powerhead that is supposedly a 235/2.6 GT motor. The tag on the midsection does confirm that this is a 1984 GT, but i am not convinced that the powerhead has not been changed over the years. What can i look for on the block itself to ID this as a true 1984 GT motor??
CB

[racer]

Top of #2 cyl is also a serial/model tag. Check the head numbers and look to see if it has scallop pistons and square ports by removing one intake cover

[76Stingray]

is the serial # on top of # 2 on the block or head?? And I am not sure what to be look ing for on the scallop piston??? Is this scallop on the top of piston?? sorry I am new to outboards.

[BarryStrawn]

The model and serial numbers are on top of the block. They are stamped into an aluminum disk that is pressed into a shallow hole. Sometimes they get painted over.

The scallops are cut into the piston skirt on the intake side. If you remove a transfer cover on the side of the block, you can see (or not) a scallop machined into the bottom of each piston skirt. On a regular piston, the bottom edge of the piston skirt is straight all the way around. You would also see the block machined away in an arc where the transfer port opens from the crankcase.

The GP/XP intake ports into the cylinder will be four sided with round corners. Regular 235 pots are overlapping round holes. This is the port near the head when when you remove the transfer cover on the side of the block.

[76Stingray]

the #'s on the aluminum disk, do these look something like a freeze out plug?? and where on the block would i find them?? front , rear,port side??
Thank you for the help....I really appreciate it!!!!
CB

[BarryStrawn]

On the top of the block above the #2 cylinder between the head and the flywheel. #2 is the top cylinder on the port bank.

It is not a freeze plug, just a small aluminum disk pressed into a shallow hole.

[76baja18ft]

xp block has cnc machined ports as opposed to the regular block having plunge milled ports....xp block has scallops at the bottom of the cylinder..
xp block looks like this..(click on picture for larger view)

.

[76Stingray]

thank you very much for the info...I will look in the morning....this disk will have the serial # on it?? same as serial on tag on midsection??
Thanks again
CB

[76Stingray]

wow...thanks 76 Baja!! will check it out in the morning. The pic is a BIG help!!

[76Stingray]

and.... the scallops are on the cylinder walls, not the piston?

[76baja18ft]

it should be in both....the scallop on the piston will line up with the scallop on the cylinder when the piston is all the way down

[76Stingray]

thank you for the info!!!!

[76baja18ft]

click on the pictures for larger versions....

regular block will have ports like this....





xp block will look like this.....




xp on the left.. regular block on the right....

[EMDSAPMGR]

Here is what a piston will look like.