Can I swap a 1980 mercury 402 powerhead with 1979 merc 402 powerhead?

[MacDaddy21]

I have a 1979 mercury 402, and a 1980 402 with a bad powerhead. I want to swap the powerhead on the 1980 with the 1979 powerhead. Can anyone tell me if this is possible, and if so, how to go about it getting the powerhead(s) off. thanks

[daveswaves]

the power heads are interchangeable but why not just run the 79 and move any parts from the 80 over to it. The lower unit is easier to swap than the power head and you should change the water pump impeller anyway. Just a thought.

[MacDaddy21]

the 79 lower unit and transom mount are in pretty bad shape, but the 1980 transom mount and entire lower unit is all in much better condition, and i figured it might be easier to swap the powerheads, but I am having trouble removing the powerhead on the 1980. not sure why.

[ONERCBOATER]

my 1976 200 came apart like a dream... but more often then not once your sure you have all the bolts out of the way...they need some prudent prying pulling tugging cussing.

Sean

[daveswaves]

OK, I see why you are keeping the lower end intact, you should still change the impeller though. For the power head make sure you have all the bolts removed, there should be 8, 3 on each side of the main block and 2 under the front intake. Often the front ones are not noticed on the first attempt. Remove the defective power head first, learn on it. The gasket can hold on to the block as well. You may have to run a knife around to separate the gasket. you can tap the knife blade in as a tiny wedge to break the seal, do not try to pry the head off. Go slowly, use lots of penetrating oil or liquid wrench on the studs, turn the engine upside down and let the fluid run down the bolts.