Johnson 1956 30hp vs. 1957 35hp

[BoatBuoy]

I wonder if anysone could tell me the differences between the subject engines. I know the 30 bore is a bit smaller, if elec. start it is 6 volt, and the wiring enters the engine differently. What are the other differences besides color scheme?<br /><br />EDIT: Probably goes in Outboard Non-Repair. Mods, pls move.

 

[rolmops]

Re: Johnson 1956 30hp vs. 1957 35hp

The '57 has a 12 volt starter not 6.<br />The standard bore of the 30 is 2.875,the 35 is 3.06<br />the 30 is 35.70 cubic inch with W.O.T. at 4000,while the 35 is 40.5 cubic inch with W.O.T. at 4500.<br />The 30 uses a J6C plug ,the 35 a J4C. That and the cowling are the differences

 

[Paul Moir]

Re: Johnson 1956 30hp vs. 1957 35hp

I thought the standard starter for the 30hp is 12v. It's easy enough to tell the difference. The 12v ones are about 3-3.5" in diameter. The 6v ones are much larger.

 

[BoatBuoy]

Re: Johnson 1956 30hp vs. 1957 35hp

If that's all there is, could a 30 be bored .030 over and result in a "35", assuming one could find pistons and rings.

 

[Chinewalker]

Re: Johnson 1956 30hp vs. 1957 35hp

Hi BoatBuoy,<br /> No - the 30 can't be bored out. The sleeves that make up the cylinder walls would be too thin. Much easier to just find a 35hp, or drop a 35hp powerhead into your 30. The bolt patterns and all long-block items should swap over. Keep the 35hp carb with the 35hp block, though...<br /><br />- Scott

 

[BoatBuoy]

Re: Johnson 1956 30hp vs. 1957 35hp

Hey, thanks Scott. I was asking because I have a 1956 boat and I would like a 30horse period-correct engine for it, rather than a '57 35horse. If the 35 was significantly different/better, I would opt for that. However, what you said makes me think a 30 would work, if I can find one. Thanks.

 

[Paul Moir]

Re: Johnson 1956 30hp vs. 1957 35hp

You would have had to raise the exhaust ports as well. <br /><br />The 30 got reincarnated as the '62-'64 28hp and the 35hp got reincarnated as the '65-'71 33hp. Both those blocks will fit right on as well, and have full needle bearings allowing 50:1 running.

 

[BoatBuoy]

Re: Johnson 1956 30hp vs. 1957 35hp

That's all good info. Just what I was looking for. Thanks all.