96 yamaha 70hp RPM in Gear

[fshndad]

Hi,

What should the RPMs be when in gear on the water? mine is at 700 rpm.

Also around 1100-1400 rpm the motor is missing a bit. I've rebuilt the carbs. Could it be the Low speed jets?

[robert graham]

At idle out of gear should be 750 to 850 RPM's....at idle in gear 700RPM's seems fairly normal to me....

[TownsendsFJR1300]

Hi,

What should the RPMs be when in gear on the water? mine is at 700 rpm.

Also around 1100-1400 rpm the motor is missing a bit. I've rebuilt the carbs. Could it be the Low speed jets?

If its idleing at 700 RPM's in gear or out, you low speed jets are probably ok..

If the engine has sat awhile with old fuel in it (over a month old, un-treated), running some Yamaha "RingFree" (on the heavy side won't hurt anything), it can only help. Its a fuel cleaner and a top end cleaner, works extremly well;

https://www.yamahapartsandaccessorie...?b=Search&d=34

Did you pull all the jets when you rebuilt the carbs and literally look thru ALL the jets? Just soaking and NOT inspecting does NOT count..

[robert graham]

Might not hurt it to take it down the river and give it a good wide open throttle run for a few miles....blow some of the old oil/carbon out of it!....

[fshndad]

Might not hurt it to take it down the river and give it a good wide open throttle run for a few miles....blow some of the old oil/carbon out of it!....

It runs good after 1600+ rpm smooth no hesitation. Its the first few hundred rpms which it's missing a bit.

I will try to run Ringfree. Does the Idle Mixture Screw control the low rpms? I've trying adjusting it and no difference. New spark plugs too!

[robert graham]

My 1999 C90 Yamaha started idling poorly/stalling, so I pulled each idle jet screw out and sprayed carb cleaner into each orifice, replaced idle jet screws and it fixed the problem!...must of been some trash in one or more of those orifices, but whatever it was, it's gone now!....maybe give it a try?....

[dngharvey]

Don't all these three cyl engines idle a bit rough? I had a 70 and now a 90 and loved em both, but they did not run real smooth till some throttle was applied. Also have a 115, it's some better but still sounds a bit like a cammed up high po at idle. Long as they don't stall and foul plugs, I'm a happy boater!

[99yam40]

It runs good after 1600+ rpm smooth no hesitation. Its the first few hundred rpms which it's missing a bit.

I will try to run Ringfree. Does the Idle Mixture Screw control the low rpms? I've trying adjusting it and no difference. New spark plugs too!

You should follow the steps in service manual to link and syc the carbs to each other.
Also set the pilot screws to spec in manual.
If it does not run well ate those settings then something is wrong in carbs or the motor itself

Sometimes opening up the pilot screws a little will help a hesitation coming off of idle.
Pay attention to the timing also. needs to be in spec and advance properly

[throrope]

Don't all these three cyl engines idle a bit rough? I had a 70 and now a 90 and loved em both, but they did not run real smooth till some throttle was applied. Also have a 115, it's some better but still sounds a bit like a cammed up high po at idle. Long as they don't stall and foul plugs, I'm a happy boater!

Yes, our TLR 90 settles down shortly after warming up and running under load. The owner's manual mentions something similar. My nerves calmed after watching a few other 90's on YouTube.

[robert graham]

Yes, our TLR 90 settles down shortly after warming up and running under load. The owner's manual mentions something similar. My nerves calmed after watching a few other 90's on YouTube.

My C90 is pretty rough compared to a newer 90HP 4 stroke, but that's just the nature of the beast....but remember the C90 is making 90HP from 70 cubic inches, so it's a performance tuned motor....not made for smooth/quiet....it's O.K.....