1958 30hp johnson running rough

3

30hpbob

Seaman Apprentice
Joined
Aug 23, 2011
Messages
34
After new points, plugs, condenser, coils my 30hp started. Lots of oil/gas in water but sort of expected that at first. Took off and ran pretty good and figured I would have to make high and low speed adjustments. But it seemed to use a lot of gas (5gals in 20minutes) and the plugs were fouling. Everytime I changed plugs it would start and run but only a short time. I doubled checked the gaps on everything. Anyone have any suggestions or help. Thanks.
 
F

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,195
Re: 1958 30hp johnson running rough

No such thing as a 1958 30hp. Nevertheless, it is gulping way too much gas. No way can it burn that much. It is just dumping it into the water. Did you adjust the high and slow speed knobs?

It should run a couple of hours at wide open throttle on a tank of gas. They are not the cleanest motors ever built and will discharge some gas into the water, but yours is way beyond reason.
 
3

30hpbob

Seaman Apprentice
Joined
Aug 23, 2011
Messages
34
Re: 1958 30hp johnson running rough

Sorry, I meant a 1956 Johnson 30hp. Yes I did adjust the low and high speed knobs. I made up a stick with a slot in it so I could turn the knobs while I was driving. I made slight adjustments and waited for the engine to respond before making more. It just didn't seem to help and like I said, it just emptyed the gas tank in no time.
 
1946Zephyr

1946Zephyr

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Joined
Oct 21, 2008
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5,556
Re: 1958 30hp johnson running rough

This has been done a few times, but it is nothing uncommon. You might also check and make sure you have the correct needle in the correct hole. The top hole should have the tapered needle with the point and sets 1 1/2 turns out from lightly seated. The bottom hole should have the blunt tipped needle and sets at 3/4 turn out from lightly seated. If it's still drinking like three Irishmen after that, then you have a float issue and it's not shutting off the fuel flow correctly. It sounds like you may need to do a carb overhaul as well.
 
3

30hpbob

Seaman Apprentice
Joined
Aug 23, 2011
Messages
34
Re: 1958 30hp johnson running rough

Thanks Captain,

I had 11/2 turns out on top needle and 1 turn out on the bottem needel and the tapered needel is on the top and the blunt on the bottom. I had already rebuilt the carburator (new float) two weeks ago. Other than checking the float of the carb. can you think of anything else I could try. Also, a lot of blue smoke as I drove the boat down the river.
 
samo_ott

samo_ott

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Joined
Jun 18, 2006
Messages
5,125
Re: 1958 30hp johnson running rough

Something is definitely wrong. It should get about 1.5 hours on a 5 gallon tank at WOT. Obviously you checked for leaks.
 
F

freddyray21

Commander
Joined
Jun 10, 2006
Messages
2,460
Re: 1958 30hp johnson running rough

one turn out on the bottom needle is way too much so something it wrong. Most of the motors I have about 1/2 to 3/8 of a turn on the high speed is about right, but do it by sound. turn it out 3/4 of a turn and start it. turn it in until is wants to die then bring it back out where it runs it's best as wide open.
 
O

OCboat

Seaman
Joined
Apr 26, 2007
Messages
73
Re: 1958 30hp johnson running rough

I don't have near the experience that most of you do but I did have a similar issue with my '66 40hp. I would check your float needle valve. I rebuilt my carb with a Sierra kit and either the needle valve or seat was defective. I put my old one back in and it solved the problem. Good luck.
 
kfa4303

kfa4303

Banned
Joined
Sep 17, 2010
Messages
6,094
Re: 1958 30hp johnson running rough

I agree with OCboat. I think you're float needle valve may be getting hung up and essentially flooding the engine. As per the previous posts, you should get several hrs out of a tank at WOT. I would just check/rebuild the carb to bet sure all is well. You may also only be running on one cylinder. These old Big Twins are surprisingly strong on just one can. May as well double check the ignition too. YOu should get a spark that can jump a 1/4" gap with a strong, blue, "snapping" spark. These links may help a bit.

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm
http://forums.iboats.com/showthread.php?t=167352
 
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