RPH Welch Plugs?

[Mumbles]

Two free six horse motors came my way recently and both powerheads have RPH stamped on the Welch plugs. Would the RPH stand for Replacement Power Head? I’ve never seen it before.

Both motors aren’t painted any color and the blocks are factory primer with the front halves being bare aluminum.

• This topic was modified 5 years, 3 months ago by Mumbles.

[fisherman6]

I would say you’re correct Mumbles, especially since they are in factory primer. I have never seen one stamped RPH either but have come across a couple motors with the red primer only on the powerheads. Those were certainly replacements. Maybe someone that knows for sure will chime in.
-Ben

OldJohnnyRude on YouTube

[PugetSoundBoater]

I have wondered what OMC would stamp on the welsh plug of a replacement powerhead, now we know.

What year are the 6 hp’s Mumbles? From the 100:1 years?

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

[Mumbles]

PugetSoundBoater wrote:

What year are the 6 hp’s Mumbles? From the 100:1 years?

I don’t know. One was on a ’60 Fisherman tower which had been converted for use on a blow boat while the other one was in a box of extra parts and they are both six horse motors as they have needle bearings on the rods big end. One T-stat had a build date of 7 – 09 on it so it’s anyones guess when they were purchased. They couldn’t have been used much as both of them have the cross hatch showing in the cylinders and when I checked them with a bore gauge, all cylinders are straight with less than half a thou wear in any of them. These blocks are rebuild material!!

Just wondering, did BRP supply powerheads after taking over OMC?

[aquasonic]

Good score there Mumbles! The price was right.

Now, I’m wondering why the “front half” of the blocks were produced without even a coating of primer, yet the “back halves” came primed? Wouldn’t the manufacturing facility have been in possession of both halves?

[frankr]

The cylinder block was dipped in the corrosion inhibitor before being machined. Since the crankcase is not submerged in water (hopefully), no need for the coating. The two are then mated and final machining done.

[dan-in-tn]

{content}Well FrankR that close! The back half (all of OMC die cast blocks) were pressure coated. Put in a pressure cooker looking vat. Then pressure was applied to force the paint into the pores of the aluminum. This was only done on the water cavities half of the block. The front half was not deemed necessary. It was don’t before machining as FrankR mentioned.
I believe these would have been OMC powerheads because they quit doing this before the end of OMC (cost savings). When powerheads were sent out lots of dealers did not paint the new powerhead for the customer. Warranty would pay to paint & allow for paint, but you had to ask? Left a bad experience with some consumers after they got the engine back. When the plants moved south the assembly procedure changed & all assemblies got painted black before final rigging.

Dan in TN

[aquasonic]

Frank and Dan, thanks for answering my questions. Always good to learn something!

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