1993 60* 150 Johnson after rebuild.

[James R]

This is the second 1993 150 I have rebuilt. The first, after a few scares, runs beautifully and is fitted to our restored Cobia BR. Some pics attached.
Ran the second motor in the tub today and appears to run but a bit lumpy. Checks show that all cylinders are firing but it coughs at idle once in a while. Evidence of even fuel at each cylinder. Bring the revs up and it has a skip at about 1500. Sparks are all there but they will not jump better than 1/4 inch on the tester. Am using 32:1 and we noticed that the first motor we did didn't like the extra oil.
Input would be greatly appreciated. This motor is to be refitted to the Nitro that it came from. We have not finished restoring her yet.

 

[jonesg]

Re: 1993 60* 150 Johnson after rebuild.

What sparkplugs are you running.?

Definately looks like theres an ignition problem with the weak spark.
Do any of the cylinders produce strong spark?
What did the rebuild consist of ?...why was it rebuilt etc, history of engine.

Nice pics, don't neglect to install a safety chain from the bow eye to the trailer frame with a safety spring clip at the bow eye.

 

[James R]

Re: 1993 60* 150 Johnson after rebuild.

Thank you for the response Jonesg.
New plugs are QL77JC4. All cylinder sparks the same. Spark is blue at each plug but not what we call fat. All cylinders are firing. Rebored all six. Not my motor originally.Had slight overheat and scored 3 Cylinders. Carbs were not that dirty but I suspect, as I did on the first motor, that the manifold sealing was not good and it ran lean.
Have now reset the timing and carb sync. I don't have the OMC tester to set the idle timing. Is there an alternative way to set this without a tester.
I can check with my timing light of course.
I very much appreciate your input.
Thanks.

 

[jonesg]

Re: 1993 60* 150 Johnson after rebuild.

Thank you for the response Jonesg.
New plugs are QL77JC4. All cylinder sparks the same. Spark is blue at each plug but not what we call fat. All cylinders are firing. Rebored all six. Not my motor originally.Had slight overheat and scored 3 Cylinders. Carbs were not that dirty but I suspect, as I did on the first motor, that the manifold sealing was not good and it ran lean.
Have now reset the timing and carb sync. I don't have the OMC tester to set the idle timing. Is there an alternative way to set this without a tester.
I can check with my timing light of course.
I very much appreciate your input.
Thanks.

Yeh but the spark has to jump 3/8ths inch.
REad this by Bill Kelly.
http://www.maxrules.com/fixomcoisignition.html

I think it entails disabling the Quickstart feature to check timing, that won't do anything for the spark but he has directions for checking the stator.

 

[James R]

Re: 1993 60* 150 Johnson after rebuild.

Thanks again Jonesq.
I am assuming that the CDI article refers to the OIS system fitted by OMC and not just an aftermarket CDI system.
I will run the timing checks this weekend per the article and see what we have.
Don't own a Fluke or a scope these days.Have a good analog and digital multi meter so the other checks will have to be secondary.
I have been advised that an intermittent sneeze from the exhaust is indicative of one cylinder running a little lean and that these motors often need jet changes to correct that.
That's a pain and not very practical for a little guy like me.
What's your take on this?

 

[jonesg]

Re: 1993 60* 150 Johnson after rebuild.

Lean sneeze , I would rebuild the carb again.
If jets need modifying I'd just order one, they screw in.
Bet its not the problem though, if one needed changing they'd all need doing.
Its very likely just crap in the carb.


You need the DVA adapter to read peak v during crank tests.
http://esitest.com/640.html

Unless your meter is "peak reading" ?