Stupid question??
 

Ok, I feel like a dumbazz for asking this but...

What do you do when you really can't find the serial numbers on your engines? I've looked above the starter for the 'pop riveted' plate and looked all over.
Non original (HP500) spark arrestors on top of the carbs so that doesn't help.

I'm pretty sure they're Mercruiser 420hp BBC because it says so on the valve cover, has Crane roller rockers (gold with 13-170 stamped on them) and GM 6269318 part number intake manifolds.

They're in a '91 Fountain Fever 29ft, and could be original but the boat definitely has later model Bravo drives than '91 (OL750035 & OL750037 serial numbers) so I can't be sure.

Just bought this thing and want to buy sea water pump kits etc but everyone wants an engine serial number.

Carbs (Holley double pumpers of some size yet unknown) also look a little damp so could do with a reccomendation as to where to send them for a rebuild if anyone could help with that too.

Any ideas gentlemen?

Since it sounds as if the motor is not original, It's hard to tell, but if it says 420hp, then they may be merc 420s (454, 420hp). I have never had to provide a engine serial number for a seapump kit. I think you just need a bravo sea pump kit. I get mine at napa auto parts or the local marine dealer.

Someone will correct me I'm sure, but i believe that the merc part numbers are as follows:

Impeller: 47-59362T1
Sea Pump Kit: 46-807151A14

Rookie from your location best friend to have is MIKES280. He will set you right up.
-Mike

Oh yea sorry meant to say he is in the Velocity section if you need to get a hold of him. Tell him i sent ya.
-Mike

Check the sea water pumps to see if they are the 1 piece plastic bodies, or the 2 piece metal bodies. Previous owner may have switched them over to the plastic bodies. If so, the part numbers listed above should be correct. The kit listed above shows that it includes the body. If you want just the impeller, wear plate, o-ring and quad ring, it is repair kit number 47-59362T6. That is for the pump with the 1 piece plastic body. If it is the 2 piece metal pump, you'll need a few more parts and I think you have to buy them separately. Go look at mercruiserparts dot com. There are basically two styles of bravo sea water pumps for the BBC's that I know of, excluding the 496's - they have their own impeller kits.