1958 Johnson Seahorse 35HP lower unit compatability

[Redhook98]

I just bought a 15-ft 1958 Norris Craft to restore and it came with a 1958 Johnson 35HP. I pulled the lower unit off the motor and found the dog clutch was badly worn (also had lots of water and a lot of wear showing on the internals). I decided to search for a different lower unit and found one in Oregon. The guy said it is off of a 1956 30 HP. All measurements and pics match up perfectly. It is Holiday Bronze as well (I though only 57-59 motors were Holiday Bronze???)

Does anyone foresee any issues with this swap? What are the years that are compatible with this motor. On some sites I see 57-59 being the key years. Others say 55/56-60. ??

The new lower unit was been tested on the motor prior to being separated. Also, it was pressure and vacuum tested and the fluid was good. It does not come with the drive shaft or the water pump housing. I figure mine will fit. (But, isn't there a difference between the 57 and 58 waterpumps?).

The casting number on this LU is 375769. The one i have installed right now is 376874.

Any insight would be much appreciated.

Thanks!!!

 

[lindy46]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

If your motor has a single water tube and no thermostat, it should work. 1958 was the year of changeover for some models to the quiet legs with the outer exhaust housing. Those had two water tubes and thermostats. I know Evinrude (Lark) made this change but not sure if Johnson changed over until 1959. I think they made a SuperSeahorse in '58 which would have the outer exhaust housing.

 

[wbeaton]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

It'll work as an assembly or you can drop the gears/clutch dog from the 30 hp into your existing lower unit.

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

I just have the one cooling tube. I did some more digging and noted that the water pump is also the same providing I do not have the thermostats. I broke a screw getting my water pump housing off anyway, so this is an easy fix. The old leg appears to be good, just worn. If nothing else, its a good supply for parts if I need. it. Thanks for the info guys!

 

[samo_ott]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

I have the parts manuals for both if you want to PM me with your email address and request then you can compare parts #'s. As Wayne says, I'm pretty sure it will swap over also. I have both those engines but have never tried to swap em.

 

[F_R]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

1955 25hp and 1956 30hp had the old style pinion gear & bearing. 1957-up 35 and 40hp has a stronger gear and bearings. The '56 complete gearcase will fit your single-tube '58, but you will be getting a gear setup that is not as strong and may fail.

And you can not swap internals from one type to the other.

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

1955 25hp and 1956 30hp had the old style pinion gear & bearing. 1957-up 35 and 40hp has a stronger gear and bearings. The '56 complete gearcase will fit your single-tube '58, but you will be getting a gear setup that is not as strong and may fail.

And you can not swap internals from one type to the other.

Well that's just not what I want to hear! Lol! So this new unit failing would be most likely a product of heavy strain on the lower end (i.e. to big of a prop, to big of a boat/load or towing-skis and tubes), right? If the boat was just for 2 people with no water sports, I don't imagine I would break it to easy, would I? These are the questions i need to ask beofre mating it up and going through the process. I am not hard on my boats and like em just to cruise. Not real "full-thottle" action or heavy hole-shots for me.

 

[F_R]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Well, horsepower is horsepower. 35 horses are stronger than 25 or thirty. So a 35hp motor running at full throttle is putting more strain on the gears than a 30hp at full throttle, no matter what size boat it is pushing.

However.....neither one of them puts full strain on the gears at part throttle "cruising". You may be just fine, I just wanted you to know there is a difference, and they changed the design for a reason.

 

[1946Zephyr]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

The internals for 35 and 40hp should work, all the way up to the 70's. The housings will be different, from the 58 Super Quiet and all 59 and up, because of the water tube set up.

Holiday Bronze was in use, from 1956 - 58 and in two shades. 59 and up was all white.

Too bad you didn't ask F_R before you purchased Oh well, it'll mount up and work, but I wouldn't work it too hard. It may be a good time to consider rebuilding your exhisting.

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

At this point I will probably use the smaller LU while I rebuild the original unit. Anyone know what it costs to rebuild one? I see LU seal kits going for $30 or so and new clutch dogs for my motor going for $50. Is there anything else? (providing the gears and bearings are good)

 

[wilde1j]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Fwd gear is usually bad if the clutch dog is bad.

 

[1946Zephyr]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

You can search fleabay or the AOMCI website. There are still a lot of parts available for these, it's just a matter of diggin hard.

 

[wbeaton]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

And you can not swap internals from one type to the other.

I've heard this before, but I can tell you that I have 1957 gears (except the pinion) in my 1954 25 hp. I and others have swapped the foward/reverse gears and clutch dog between 25-30-35 hp models with no problems even though they are a matched set. It is true that the 25-30 hp lower unit isn't as strong at the pinion.

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Well you guys talked me into it. I am trying to return the unit that I bought from the 56. I found a lower end off a 1958 Evinrude that is good and ordered that. I still plan on rebuilding the old unit and/or use it for spares. I just would not feel comfortable crossing to Potomac on my way from the house to the marina with a weak lower unit like that. With my dumb luck I will be caught in the middle when a squall pops up in the summer. Doh!

 

[F_R]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

I've heard this before, but I can tell you that I have 1957 gears (except the pinion) in my 1954 25 hp. I and others have swapped the foward/reverse gears and clutch dog between 25-30-35 hp models with no problems even though they are a matched set. It is true that the 25-30 hp lower unit isn't as strong at the pinion.

Well sure, some of the parts are swappable. But obviously the pinion and pinion bearings are not.

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Just disassembled the lower unit of my old engine. The dog clutch actually looks near new after I had a good look at it and knew what to look for. The gears look great as well. The clutch fork though is bent to hell. Looks like something let loose down there at one time and they bent it back into shape. Yikes! Anyone know where to get one of those?

The drive shaft looks new also. When I got the boat, it had an old drive shaft sitting in it that was badly abused. I guess I know why now.

Guess I should not have jumped the gun and bought two more lower ends that I do not need. Oh well, good for parts. I would like to find a clutch fork separately so as to keep the other units whole though. The LU I have had so much old frothy-oil and water in it, it looked like toast. Live and learn I guess.

 

[samo_ott]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Dang. Got pics of the mint clutch dog and gears and LU? We love pics!

 

[Redhook98]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Nope, no pics yet. The story gets better. After stripping the paint from the LU, I found it had a nasty crack in it. Looks like it is back to being a parts-only unit. Lol! My luck.....

 

[HighTrim]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

Send it to me and Ill dispose of it for you

 

[samo_ott]

Re: 1958 Johnson Seahorse 35HP lower unit compatability

How nasty? If it was hidden by paint it cant be that bad? If it's a hairline crack it can easily be welded using aluminum rods like Durafix or something and a propane torch. I have done it and it works well.