Low idle adjusting--out of water

[Huskie]

I need to adjust the low idle on my 70 hp johnson. Can I do this using a hose with the muff's on it. I thought I came across an earlier thread that warned against too much water pressure, any ideas?

[Valv]

Yes you can do it with no problem, just check with a manual for correct settings.

If you can do it while in water it would be better, since idle rpms have to be set with motor in gear, you could just back boat into lake without taking it off trailer, just enough to have prop and water intake submerged.

[Surface Tension]

Yes you can do the low idle speed adjustment with muffs on.

Hook up the muffs and turn the water on before you start the engine. Some inboards you have to be careful about too much pressure and volume.

[FL SNIPER]

Out of curiosity, which outboards should you be careful with too much water/hose pressure? I have a 4 stroke 40 HP suzuki that i put the muffs on from time to time...seems to work well and I don't believe I'm causing any damage. But what should a guy look for so he doesn't mess anything up? Thanks.

[musky hunter]

While low idle can be adjusted using the hose muffs, it is not as good as adjusting while acutally in the water. The reason: underwater exhaust has back pressure not present when you run your motor to the atmosphere. You may not have a satisfactory result and be prepared to do some additional tuning on the water. I hope I'm wrong, and that your motor purrs like a kitten on low idle this Saturday morning. But my experience is the best idle is always found with the motor in the water.

[Huskie]

I was having trouble last year, it would start fine after a few hours of drifting or trolling with the minkota, but when I put it in gear it would die on me. If it happens on the water I will try to adjust it then too, thanks. Winnie in a week!!!

[marine_man]

I think you're going to get your best result in the water as well. The exhaust backpressure will make a difference, as will the load of the motor pushing the boat when you adjust it in gear... there isn't any load on the motor when it's out of the water and will idle lower in the water than when out of the water.

marine_man

[Surface Tension]

FL SNIPER, that was a goof on my part. I meant to say some inboards.

[FL SNIPER]

Thanks Surface Tension.

I just wanted to be sure I wasn't screwing up my motor by turning the hose, water pressure up to much.

This site is great because there are many knowledgable guys like yourself who share their advice. And no question is too small or too big for you gentlemen either. Thank you.

[musky hunter]

That is a symptom of too thin a mixture. I'm speculating that it starts with the choke but then dies. A quarter turn richer may fix your problem. Also, make darn sure your plugs are good.

[Huskie]

70HP Johnson, where do you adjust the mixture to get it a quarter turn richer??