Oberdorfer pump for M25 question

[Harlan]

My '83 OD34 has an M25 engine. I'm looking for help installing a new raw water pump. The old pump is an Oberdorfer with a tag 202M-7. It appears that a N202M-07 is the replacement. That has a round mounting flange with mounting holes in 2 ears. While my old pump has those holes they are not used. Instead 2 smaller holes have been drilled closer to the pump body (ie, smaller bolt circle) that are used to mount to an adapter plate on the engine. I do not find those holes on any stock pumps. I ordered a stock pump from Depco and planned to machine the mounting holes myself.

Here's the problem. The old pump had a more or less round body with a grease cup. There was plenty of room to drill the mounting holes with room to spin a nut. The new pump has a square body with a zerk fitting. It apparently is a factory redesign. The Oberdorfer website still shows the round pump body for the N202M-07. The parts store here shows a square body but grease cup. Continuous improvement I assume!

The square body is bigger. There appears to be enough room to drill the holes but one will be close to the body. I'm concerned about having enough room to turn the nut. Anyone have a similar pump arrangement with these mounting holes? Have you changed to a square body pump and does it fit properly?

 

[Skipper]

That's the wrong pump for that engine.
It originally came with a Sherwood.
Someone decided to replace it with an Oberdorfer 07, maybe because that's all they had, and did a kluge adaptation.
Remove the adapter plate. Use a 16.
I think SBO (this site) might have them, or https://www.catalinadirect.com/inde...ump-replacement-or-retrofit-12-oberdorfer.cfm

 

[LeslieTroyer]

@Skipper that engine came from 82- at least 83 with the -3 pump. The early ones (-3 & -7) came with a male/female shaft adapter and mount spacer. They switched to a -15 later in the production cycle ( a -7 May have been in between) I don’t think the Sherwood’s came along until the XP or XPB models. The -3 has much less flow than the other 3 models.

I would replace it with a -15 or -16 to get away from the grease cup and the ability to pull the shaft and not worry about the shaft adapter falling out of alignment. Pumpsandparts.com will give you a discount for CIA36 members.

Which ever model you choose, loose the snap ring it isn’t needed according to the factory.

 

[Harlan]

Thank you both! Went to the boat today and removed the adapter. Looks like a change to the 15/16 will work perfectly. I called Depco, returned the -07 and they are shipping a -15 and gasket. Very helpful and no hassle. (I went with the 3/8" in/out as that eliminates additional plumbing changes.) I noted that the adapter appears to accommodate the standard bolt holes on the -07 except one bolt would end up under (and rubbing on) the alternator belt. That must be why it was reworked with the odd holes.

This will be a very positive change - thanks again.