Still won't idle 2000 Johnson Jet

gman01

Recruit
Joined
Nov 26, 2008
Messages
4
I previously posted the the below msg concerning my 2000 30JRSSB having problems not idling properly. I have sped the idle speed up a bit and have been using it, as it runs fine other than when the butterflies are all the way closed. Sounds like one cylinder is soemtimes missing at low RPM's. I have rebuilt the carbs, checked compression, (135psi in both) replaced plugs, replaced a leaking gasket between the powerhead and lower end and it still has the same issue. When running it in a tank, I notice that exhust fumes are coming out of other areas on the lower end than just the exhaust outlet on the back. I have not dug into the lower unit to see how the exhaust is suppose to flow and if this is an issue or normal and the shop manual I have is not real clear. In the shop manual it does say that back pressure can cause idle problems. Anyone have any experience with this? Or any other suggestions on what to look at next? I haven't checked timing, but the way it runs for all other speeds, and the fact that the timing adjust rod is at the exact 2" noted in the manual, I'm not sure that justifies me purchasing a timing light just to prove it out. Thanks!


I previously had a thread concerning my 2000 Johnson 30 Jet The model # is J30JRSSB concerning idle problems (very rough idle, won't stay running). Got some great advice recommending carb rebuilds and I have done that, unfortunately it didn't resolve the issue. I have now noticed that there is some oil and water dripping out from between the Power head and the lower unit (remember it's a Jet). Now I trying to decide if this leak could cause the problem I am having with idle. I also see one of the bolts is broken off that holds the Power head to the lower unit. Just trying to determine if I get a power head gasket set will it have the gasket I need and will it likely address my problem with the idle. I don't want to overhaul the powerhead, as the compression in both cylinders is 135 psi, so that shouldn't be an issue. I am also trying to deside how big of job this is and if I should just decide to take it into the shop and pay the $95 hr to have them work through.

Has anyone seen this problem before - or know why a leak in this area would cause an idle problem? How big of job is it - the shop manual isn't real clear and only discusses rebuild. Thanks in advance for your feedback.
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,174
Re: Still won't idle 2000 Johnson Jet

A leak which causes idle problems usually has a telltale sign such as steam cleaned plugs or low compression, you don't have that.

Have you used a spark gap tester to check idle spark?
 

Harker

Chief Petty Officer
Joined
Sep 21, 2003
Messages
452
Re: Still won't idle 2000 Johnson Jet

If exaust is getting sucked up under the hood, it will choke out the motor. There are two gaskets below the powerhead. One seals the powerhead exaust and the other seals between the midsection and pan. Either can let a lot of exaust out to get sucked under the hood. Look to see that the idle relief on the back of the motor isn't clogged and that a mouse hasn't packed crap in the lower.
 
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