Info on NOS 4 HP Powerhead -- Corrected Part #

[SolingSailor]

Hello to the group,

I recently purchased a new old stock 4 hp powerhead, and I have some questions:

The powerhead came with intake manifold, reedplate, head, and of course pistons and crakshaft, all assembled. There is no exhaust cover. Is this how these powerheads are typically supplied?

The seller does not know the year of manufacture, or which models this powerhead may fit. The crankcase shows p/n 389522 (this is the correction). The head is p/n 325325.

Would anyone know which year or range of years this powerhead was used?

Thanks for your help.
--Mitchell

 

[Rick.]

Re: Info on NOS 4 HP Powerhead

Re: Info on NOS 4 HP Powerhead

You can go here and search for yourself or post the model number off the tag on the transom bracket and someone will know the year from that. No it isn't common to ship motors with parts not installed. Best of luck. Rick.

http://epc.brp.com/Index.aspx?lang=E&s1=4fb44c75-0b63-4cb0-a52e-196fa4ece40d

 

[SolingSailor]

Re: Info on NOS 4 HP Powerhead

Re: Info on NOS 4 HP Powerhead

Hi Rick,

Thanks for responding. This is not a complete motor, just the powerhead.
Hence no transom bracket and no tag. No midsection, no lower unit, no covers. There is also no stamped disc installed.

 

[jay_merrill]

Re: Info on NOS 4 HP Powerhead

Re: Info on NOS 4 HP Powerhead

Look for the welch plug on the top of the powerhead - it should be towards the rear of it. At a minimum, there will be a serial number on it and there may be a model number, as well. Post whatever information you find, and we can go from there.



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[SolingSailor]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

Thanks Jay,

There is a plug on the top near the rear, but it is small, like 1/4", and has no numbers on it. I don't find any other numbers anywhere on the powerhead.

One other thing -- I read the crankcase number incorrectly originally. I have edited the original post with the correct number, 389522.

--Mitchell

 

[jay_merrill]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

Where did you buy the powerhead? Can the seller tell you the year?



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[SolingSailor]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

Jay, thank you for responding,

No, the seller does not know much about it. It seems to be in new condition, and I am thinking of assembling a working motor from it. It is drilled and tapped for a fuel pump, which suits my purpose.

If I can learn the year, I can easily order parts for it.

--Mitchell

 

[jay_merrill]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

I just went out to my shop to look at an early 70s 4hp Johnson that I own. The welch plug is on the starboard side, right below the fuel pump. Mine has both the "M" symbol and the serial number of the motor on it.

I am beginning to think that whoever sold you the powerhead that you bought, is not telling you the truth. Where did you get it? Is it something that you found on EBay, Craigslist, etc.? Are you sure that it is new and not just repainted?

Also, if you can take a digital pic and post it here, I might be able to tell you if what you have, really is an OMC 4hp powerhead.


PS: When you say "drilled and tapped for a fuel pump," do you mean that the original mounting bosses are present on the casing, or do you mean that someone drilled and tapped the casing to mount a fuel pump? If the latter is the situation, this is probably not an OMC 4hp powerhead. Further, if such drilling and tapping was not done on a bypass cover (which the OMC 4hp powerhead doesn't have), the powerhead could now be junk.



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[SolingSailor]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

Hi Jay,

I did buy it from ebay.

The powerhead was cast with the holes and bosses for a fuel pump. I meant that it was designed for a motor with a fuel pump, and not an internal tank or pressurized tank.

There are no other serial numbers on the motor. It has some cast in logos, which are identical to ones on my other 4 hp. I don't believe spare powerheads come with serial numbers. I have purchased new (meaning never used, but made in the '80's) crankcase and cylinder assemblies from the shopatron/evinrude site, and there were no serial numbers. My original powerhead, which I replaced, had a disc with a serial number matching the model number tag on the transom bracket.

I will try to get a photo, but this is what I am pretty sure of:

It is a genuine OMC powerhead.
It has never been installed or used. The pistons are pristine, crosshatch visible on the cylinder walls, water passages totally clean, not painted, just a new looking assembly.

The questions I have are does such a spare parts assembly usually come without an exhaust cover? But more importantly, if someone knew offhand what years the part numbers I cited were used, it would be easier to either buy more parts, or use this powerhead for its parts. I would also know what kind of bearings are used on the crankshaft (and thus the oil ratio) without breaking the halves apart.

I suppose I could spend a few hours searching manually through the OMC parts diagrams, hoping to get lucky.

Thanks for your efforts on my behalf.

--Mitchell

 

[jay_merrill]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

I have not been successful in cross referencing your part number with a powerhead of any particular year, but I am going to take a guess that it is from the 1978 manufacturing year.

The closest that I have found, is a 389502, which is a crankcase & cylinder assembly for a 1978 OMC 4hp motor. That assembly does not include the pistons, connecting rods and crank, so it is less than a complete shortblock.

OMC made 4hp motors from 1930 - 1932 and from 1969 - 1979. I think we can rule out the 1930 - 1932 range, so that leaves us with the later motors. During the 70s, the major difference between the engines, was the use of magneto ignition systems, with ignition coils, condensors and points under the flywheel in the pre-1977 motors, v. the stator, sensor, charge coil & external ignition coil setup of the 1977, 1978 & 1979 motors. Your powerhead, of course, has none of these things currently attached to it, so figuring out which it is, is the "fifty dollar question."

I recommend that you call an Evinrude dealer, to see if they can tell you anything about the part number that you have. You can contact BRP too, but they tend to push callers to the local dealers, on any question pertaining to older motors.



???

 

[SolingSailor]

Re: Info on NOS 4 HP Powerhead -- Corrected Part #

Thank you Jay. You've gone beyond the call of duty researching that for me.
I am now pointed in the correct general direction.
--Mitchell