Johnson Motor identification help needed

[tharmon01]

I purchased a Johnson outboard motor recently and am having trouble identifying it. The identification plate shows Model number as RX-11A with a SN of 2335270. The ID plate also states that the motor operates at 28 hp at a 4500 rpm range.

However, the motor cover states Johnson Super Sea horse 33 hp electric

Ive searched on many different sites and cannot find this Johnson model number of RX-11A anywhere. Based on how the cylinder head looks compared to the diagrams on iboats it seems that it could be anywhere from a 1962- 28 hp to a 1964 - 28 hp, but I really cant tell.

The cylinder head has a number stamped on it of 30905?. I cant seem to find that part number anywhere either. I'm adding a few pics of the cylinder head.

Can anyone help me identify this motor and cylinder head? i'd really like to get this engine running.

Thanks so much in advance.

Todd

 

[Joe Reeves]

RX-11A is a 1963 28hp Johnson

If memory serves me correctly... the 28hp was reached at 4500 rpms with the maximum top rpm being at that time 4800.

 

[F_R]

You have the head off, so measure the bore. A 28hp is 2-7/8", and a 33hp is 3-1/16". Motor covers will fit both.

 

[jimmbo]

That looks like a 28 hp cylinder head, a 33 hp head would look a lot different

From the 1963 brochure, some info