V4 Johnson 115 - Sputter - runs rough at idle

[Ipswichwhaler]

I like these old V4 engines... looks good on my 1964 16-1/2' whaler Katama. But mine sputters at idle and low speed.... runs rough. She smokes (could be my oil/gas ratio) yet at WOT she the sputter goes away (of course). Bottom line is she just doesn't leave me confident to allow my youngest daughter to take her out for a day on the water.

In my area (Northeast, Boston) for some reason mechanics don't like to work on the older models. One place told me that the carbs are worn and need to be replaced. He did a link/sync and turned up the idle. Runs a little better but I am just not happy..

Snapper in Australia had a similar issue. His engine is now running like this --> Smooth Running V4

DAMN! If I could have mine run like this I would be ecstatic! When she first starts it sounds like she is not running on all 4 cylinders. After I giver her a fast rev she blows by her stumble and will idle. Eventually she begins to sputter. I've looked through the sputter threads. I found one by Snapper Fisho who got to the bottom of his issue. Hopefully I can get there too!!

I've:

• replaced the thermostats
• cleaned out the water cavities (all the sand over the years)
• new head gaskets
• new plugs
• new wires
• new carb kits
• new water pump
• I can post compression for each cylinder.

What next? Timing with a light? Inspect the carbs again? Thoughts????

Thanks!!

[bigtime_mcalpine]

I’ve never seen the carbs on these to confirm but my first step would be to inspect and clean the idle passages in each of the carbs. Make sure all the small openings into the carb throat are nice and clean. You could put a new carb kit in each but if you have not ensured that the tiny idle passages are clear of crap then it won’t make a difference.

[racerone]

Model # of this engine.----Compression tester is the first tool to be applied to these motors.----They are world famous for broken piston rings.----Post your numbers.----The motor in the video could still run smoother.------And no the carburetors really don't wear out.

[Snapper Fisho]

Hi Ipswich Whaler,
I would carefully clean and rebuild both carbs and then make sure you have synchronized both carbs precisely so they close and open at the same time.
In the video you posted from my thread back then, it was prior to my last post where I tweaked the carbs linkage and synch even more. It is actually idling and running a bit better than that and it's been a brilliant motor for me for 40 years now.
Hope you get the same outcome, as long as your compressions are good and relatively even.

[Ipswichwhaler]

Model # of this engine.----Compression tester is the first tool to be applied to these motors.----They are world famous for broken piston rings.----Post your numbers.----The motor in the video could still run smoother.------And no the carburetors really don't wear out.

Ya I was suspicious when I was told the carb was "worn out"

I'll pull some numbers and post them. What would be acceptable compression numbers?

Unfortunately this engine I don't think has any model plates on it to provide any identification. I will post some pictures with hopes that will give everyone an idea what I have.