I have a merc 454 mag mpi and I would like to check the impellar for any damage. Is there any way to check this without taking the whole thing apart?

no you need to pull the 6 bolts and take it out and at that time id just replace it. if your water pressure is good its probaly fine.

It seems to pump fine and my water temp is not bad but it is still the original one and I have 300hrs on it.

If you boat in fresh water and arent near sand, I have seen them go to 600 hours before replacement,,,, Personally,,, if you are willing to take it apart to check it,, put a new one in. Cheap insurance.

I rebuilt mine on the dining room table. Took about 1 hr., including the slick new epoxy paint job. I used new bolts (old ones had been chewed up by Bubba), new gaskets & impeller. Total parts were around $30.

Cheap insurance & peace-of-mind.

D. Ocean
Pompano Beach, FLA

Gee... I hope you put some newspaper down so that your didn't get any food in your pump....

I haven't tried to take it apart yet. Do I take it apart from the front where the pully is or from the back where the hoses go into it?

from the back pull the 2 hoses off and take the 6 bolts out and pull the housing off, the impellar is in the plastic housing push it out and twist and bend the new one in the fins dont need to be a certian way so if some are one way and others another thats ok as soon as you start it they will all go to one direction. not a hard job at all.

good luck