56 30hp Johnson different power head?

[89Aluma]

Hi there, so I was searching for a different motor since my Mercury died on me. And came across a 56 Johnson 30 hp Rd-18. It's tough to start but does start with some persuasion a little squirt of gas into the carb so I figured it probably needs to be cleaned and rebuilt while inspecting the power head some more I noticed it had evinrude freeze plugs and different shaped heads than what I had seen in most pictures of this model. Then noticed it was blueish greenish color like the old evinrudes. The head has pert rides out a little and has a spring sticking out of each cylinder. I think it may be a evinrude 35hp. Not to sure but I need to order a rebuild kit for it so I can work out the kinks here but don't know what to order for. I'll try to post pictures

 

[89Aluma]

No Title

 

[jimmbo]

You have a bit of a FrankinJonRude. Power head looks like a Evinrude. The head looks like it's from a 1957 35 hp or a 58 BigTwin and has the Compression Relief System, that's what the springs are about, but the linkage from the recoil starter to operate it is not there. The pressurized fuel system has been replaced with a fuel pump. I don't know if the head from a 35hp will work on a 30 hp as the bore is different. The 30 hp has a 2 7/8 bore and the 35 3 1/16 bore. A head from an Evinrude may be different from a Johnson due to the different style of cowls and how they attach to the engine. If a 30hp powerhead was replaced by a 35hp powerhead, the carb may or may not be the correct carb. The Air Silencer looks like the one from a 30hp.

 

[F_R]

Did you buy this motor, or are you just considering buying it? If just considering, run while you can. Otherwise, be prepared to do some work and spend some $$. Start with the ignition system. If it has already been replaced, fine. But otherwise expect to replace coils, points, condensers & wires.

As already said, the Johnson and Evinrude hoods are not interchangeable. So that brings up the question, are you going to do all this only to find out later that the hood won't fit?

 

[Chinewalker]

The Johnson cowling will fit just fine on the Evinrude powerhead IF you use the Johnson recoil mounting brackets, which I think I can see in one of the photos. The Johnson brackets have the brass nubs that hold the cowling bumpers. The cylinder heads are the same, although the Evinrude head would also have the Evinrude cowling bumpers bolted onto it. Both heads have the ears for the Johnson cowling cast into them.

 

[F_R]

That's correct, I'd forgotten how the hood bumpers work with either head.

 

[89Aluma]

Well I picked it up for $175 and the Johnson hood fits on it, fits well actually. And once it gets started it runs really really well good throttle response and good rpm range gets to full throttle fine. Just tough as nails to start probably due to the compression relief system I had the low speed 1 and 1/4 out and the high speed at 1 and 1/8 out I wonder how hard it would be to get my hands on that compression relief system. It would probably start considerably easier with that. Right?

 

[82rude]

Good news is all parts are the same between the 35 and 30.carb kit ignition parts.

 

[F_R]

The compression relief system does NOT make it start easier. It makes it easier to pull the rope. But if you are strong enough to pull the rope fast enough, it will actually start easier with the compression relief disabled. In other words, it's all about pulling the rope.

 

[89Aluma]

Ok, it's a real beast to start so my plan of action is to pull the carb disassemble it clean it reassemble it and and bolt that back on. While I'm at it and since I already have the tools to do it I'll pull the flywheel and and see how old it all is under there I'm thinking since it's obviously had a power head swap that someone hopefully took the time to replace coils condensers and points... If not I already found them there pretty cheap compared to Mercury parts!! So if the coils and all look good I may try to readjust the points back to 20 thousands. As indicated on the flywheel and see where that gets me other wise since it runs smooth I think the jets in the carb are plenty enough, is there a primer system on this carb though??

 

[oldboat1]

Interesting project. It's an easy electric start conversion too -- can keep an eye out for parts (essentially, starter, bracket, and ringed flywheel.)

 

[89Aluma]

I'll do my best to keep it updated!!

 

[jimmbo]

Primer system? Well there should be a primer bulb in the fuel line, engines from this era use a choke on the carb

 

[89Aluma]

Ya I was just curious about it because my Mercury has a bulb that when you pull the choke it squirts a little gas in to help get her started up. I looked again and see nothing of the sort on the carb wasn't sure if it was suppose to have it or not

 

[89Aluma]

So the 35 hp is still tough to start upon further inspections I think I'm missing the "packing" for the carb needles, could this cause hard starting

 

[F_R]

The primary purpose of the needles packings is to keep them from spinning due to vibration. They really have no effect on starting. Possibly a small effect on idle quality if the slow speed needle packing is really leaking badly.

You said you have the H/S open 1-1/8 turns. That's way too much. 3/4 is enough for initial startup with fine tuning at full throttle on a boat on the lake. It will probably end up about 5/8 turn out. Like I said, on a boat, on the lake.

 

[89Aluma]

The primary purpose of the needles packings is to keep them from spinning due to vibration. They really have no effect on starting. Possibly a small effect on idle quality if the slow speed needle packing is really leaking badly.

You said you have the H/S open 1-1/8 turns. That's way too much. 3/4 is enough for initial startup with fine tuning at full throttle on a boat on the lake. It will probably end up about 5/8 turn out. Like I said, on a boat, on the lake.

Thank you very much supreme mariner I think I'll order a carb kit and just rebuild it 100% including pulling all the passage plugs and cleaning the crap out of them. I pulled off the fly wheel to look at the ignition system it all looked fairly new point were just a little over 20 thou. I re adjusted them and reassembled it but no noticeable change, I have to have the plugs touching the block to get a spark, not really the strongest spark ever but should be enough to do the job I think I'll just replace the points coils condensers and see how it does

 

[boobie]

Your spark should jump a 1/4 " open air gap on a spark tester. The way you're testing the spark doesn't tell you anything.

 

[89Aluma]

For anyone who was wondering, I strapped this motor to the boat and took it out for a bit and it is purring like a kitten, I converted it to electric start and that worked great pull starts a lot easier to