Backpressure/timing ?

[BigNiner19]

Some of you know that I have had a whale of a time trying to get my johnson to idle in nuetral or even in gear at low RPM's. Ive cleaned the carbs, I've done all kinds of new parts, and the motor runs FANTASTIC at fast idle all the way through cruise and WOT. But just will not sit and idle while in water.

Now here is the dilemma. I now have the boat idling FOREVER on the hose. But when I get it in the water, it will die. I can leave it sitting in nuetral forever it seems like while its on the hose. But somehow, the backpressure is killing it.

Is this a timing issue? Sometimes I can move the throttle (out of gear) up just a little bit and keep it idling for a little while in water. But its still just not right.

Motor is a late 1988-1990's 60HP.

Cory

 

[JUSTINTIME]

Re: Backpressure/timing ?

you need to adjust ide in gear and warmed up in the water'have you done that?

 

[Dhadley]

Re: Backpressure/timing ?

Let's start with the basics. What motor do you have? There were a couple versions of a 60 hp in the years you mention.

 

[F_R]

Re: Backpressure/timing ?

At idle speeds, the carburetor throttles are closed (or should be). So idle RPM is purely a matter of spark advance/retard. Check your linkages and make sure the carbs are actually closing. If one or more is hanging open it will mess up the idle.

Otherwise, I really think you probably have a sick engine. Stuck rings, scored pistons, something like that.

Either that or it is not firing on all cylinders at idle.

 

[BigNiner19]

Re: Backpressure/timing ?

you need to adjust ide in gear and warmed up in the water'have you done that?

yea, I did that as best as I could. I think I've got it really close.

Dhadley - I honestly dont know which version of 60HP I have. I brought the motor to two evinrude/johnson dealers and they came up with the same conclusion I did, but just looking at the part numbers and motor that it was definitely a late 1980's or early 1990's motor.

There are no productions numbers anywhere to be found on the transom bracket/freeze plug or anywhere.

F_R - I'll have to check to see if the carbs are staying open or completely shut. Its so annoying, because the motor runs FANTASTIC other than the fact that it will just cut out if it sits in nuetral for longer than a few moments.

 

[HighTrim]

Re: Backpressure/timing ?

Your idle should be 650 rpm under load in gear. Were the low speed jets thoroughally cleaned when rebuilding the carb?? Removed and cleaned behind??

 

[BigNiner19]

Re: Backpressure/timing ?

Your idle should be 650 rpm under load in gear. Were the low speed jets thoroughally cleaned when rebuilding the carb?? Removed and cleaned behind??

Yea, I cleaned them real good the 1st time. Then again a second time, thinking I must not have cleaned them good enough. Im not sure what the deal is. Why will the motor idle ALL DAY long on the hose, but not in the water? I wish I had a tachometer.

Cory

 

[F_R]

Re: Backpressure/timing ?

I suggested earlier that the motor may be sick. I guess you didn't want to hear that. Most carburetor trouble is not carburetor trouble at all. That is probably the case here.

You simply have to start with the basics. What is the compression? Is it running with equal power on all cylinders?

 

[Ranger 330V]

Re: Backpressure/timing ?

you guys think the reeds may be getting a bit weak?? I know alot of times they'll do great all around except at idle because the reeds are weak. Sometimes I know that if you'll keep your motor trimmed up some while idling around its alot easier on the motor...trim it all the way down then back up..(not out of the water) make sure the lower unit is down in the water...you'll notice a difference in rpms...not much..I know my old merc would load up if you left it trimmed all the way down to long...I know thats not a "fix" but could allow you to idle if it will idle on the muffs...worth a try till you can fix it.

 

[F_R]

Re: Backpressure/timing ?

Yes, actually I did consider a bad reed. Not "weak" but one of them may have a foreign object caught under it. If that is the case, it would be low on power on that cylinder.

Did I mention is it running with equal power on all cylinders?

 

[Dhadley]

Re: Backpressure/timing ?

We still need to know which motor you have. How many plates are covering the exhaust on the port side of the block? 3 or 1?

 

[Ranger 330V]

Re: Backpressure/timing ?

my fault..yeah you mentioned that...didn't think about that. Not trying to mess up the thread..but something can actually get caught under a reed?? I guess like a chuck of carbon or something??

 

[CharlieB]

Re: Backpressure/timing ?

I suspect idle air bleeds are restricted and or idle passage(s) still not clear

Test, pull off the airbox so you can use your hand to mannually choke, block off a large portion of the airflow to each carb, see what, if, orany change in the idle behavior.

If it begins to idle choked in the water then you pretty much shown that it needs moore fuel, get back into those carbs again

Float level is critical to idle mixture, usually setting the float dead on level with the carb inverted is fine. From there you can 'crutch' the idle mixture fatter or leaner by changing the float 1/16 but NO MORE THAN 1/8 inch higher or lower

BE SURE that all idle passages, air and fuel, are CLEAR, use carb cleaner (spray can) followed by compressed air, shop air hose not a can of air to blow dust out of your keyboard!