1955 Johnson 25 Hp Seahorse Questions

[Shakedownscott]

Hello,

First off I have to say this site is awsome, there is a lot of great info here. I am a big fan of older Johnson Seahorse engines. My current boat has a 1962 5.5 Hp Seahorse outboard which I love. It has been a great fishing companion and was my father-in-laws before he passed.

A few years ago I was given an RDE-17S, Johnson 25 Hp outboard. I am really happy to have this motor, to me it is the big brother to my 5.5 Seahorse. I can't believe someone was just giving it away. At the time I got it, she had good compression but no spark. It is really clean under the cowel and looks to be in great shape.



I recently bought a 16 ft Starcraft Seafarer to put this motor on.



I purchased a ignition rebuild kit, impeller and ignition wires from iboat. Now the boat has a strong spark and it started right up in a trash can. I don't have a two line tank so I blocked the pressure line coming from the crankcase and put a one line tank up on a ladder for positive pressure.



Now that I know this motor runs I want to upgrade the engine with a fuel pump. I am hoping I can do this cheaper than buying and restoring a two line tank, they are rare and usually rusty around here. I found a lot of great info on this site about doing this but I have a few questions.

It looks like later model fuel pumps are attached to the bypass cover, it is done this way on my '62 Johnson. Can I just drill and tap a hole thru the bypass cover and screw the pump to the bypass cover? I am assuming this hole would give the pump the pressure/vacuum cycle it needs to operate?



My biggest concern is that I don't starve the motor for fuel and cause it to loose lubrication. Can I just buy a 25 Hp or up fuel pump off a newer motor and adapt it? Are there pumps that are more suitable for this than others?

Thanks in advance for the help.

 

[1946Zephyr]

Re: 1955 Johnson 25 Hp Seahorse Questions

You can get a fuel pump and bypass cover from a 28hp of the '60's era.

 

[Shakedownscott]

Re: 1955 Johnson 25 Hp Seahorse Questions

That's great thanks. I will start looking for a '60's era cover and fuel pump from a 28Hp motor. Did the 28 Hp motors replace the 25Hp ones? Or are they the same basic motor?

 

[1946Zephyr]

Re: 1955 Johnson 25 Hp Seahorse Questions

Well, oddly enough, the 28's were a continuation of the older 25's and 30's but with a more modern look, by replacing the aluminum clamshell shroud, with a fiberglass hood. The 33's were a continuation of the older 35's with the same concept of the 28's. 95% of the parts on these are replaceable with what is on the 25, 30 and 35 in the '50's. They even have the same engine blocks, lower units, ignition systems and the like. Really, the only basic changes are in the shrouding and carburetors. The midsections are pretty close, but slightly changed to accomodate rubber shock absorbers for the lower shroud. What is really funny, is if you look at the head on the 33, it still comes from a modified casting that was used for the old 35, from '57. They still even have the mountings, for the compression release actuator, but of course, the 33 never had the compression releases. So, bottom line is, the 28 had the 35.7 cube block, that the older 25's and 30's had and the 33 had the 40.5 cube block, that the older 35's had.
The '58 and '59 35's with the Super Quiet design though did have a different block design, because of the thermostat and different cooling system.

 

[Shakedownscott]

Re: 1955 Johnson 25 Hp Seahorse Questions

Thanks, that is very helpful info. I am happy to hear that there are so many interchangable parts over different Hp ranges and model years. This will hopefully make finding parts easier.

I found some parts diagrams online and was up way too late last night combing thru them for info. So far this is what I have found out:

Up until '63 they had what looks like a remote fuel pump with a sediment bowl integral to the assembly. My carb already has this bowl, so I am going to look for a later model pump than these. When done I would like this to look as factory as possible.

The '64 28 Hp motor looks to have what I am looking for with regards to the bypass cover and fuel pump. These same part numbers were carried forward to the following years and Hp's:

1965 33 Hp
1966 33 Hp & 40 Hp
1967 33 Hp & 40 Hp

In 1968 the bypass cover and fuel pump part numbers change but has the same bypass cover gasket number. I am assuming that should mean these would still bolt up but are somehow different? Does anyone know if you can interchange the '68 and later fuel pump & bypass cover onto earlier 60's motors mentioned above?