45 hp Chrysler runs rough low speed-better at high speed>>>>>

skizawa

Cadet
Joined
Dec 9, 2016
Messages
24
Running in a very low speed the boat shakes. Put it in neutral it pretty much smooths out. Up on a plane it runs just great and smooth. I had the prop re-conditioned and still had same problem. Lower unit has new oil.
It's a 1985 45hp Chrysler.
Any info from you gents would really be appreciated!
Thank You!!!
 

Chryslerman123

Petty Officer 3rd Class
Joined
Nov 18, 2016
Messages
87
Could the prop still have an unnoticeable slightly bent blade? It doesn't take much damage for a prop to cause vibration and from my experience the vibration usually happens at a certain RPM. Also maybe could be a bent propshaft?
 

Chryslerman123

Petty Officer 3rd Class
Joined
Nov 18, 2016
Messages
87
Forgot to mention... To check the propshaft-remove the plastic prop cone(not sure if that model has a prop cone) and look straight at the end of the propshaft. With the engine not running and in neutral spin the propeller and see if the prop shaft moves side to side any (wobbles). If it spins perfectly center then your prop shaft is fine.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
Rough running at low speed could be the prop, but since you just rebuilt it???
​Hook up a hose and see if there's any wobble.
Then remove the prop and see if the shaft has any wobble.
The low speed jet in the carb is more than likely the problem.

​To set the low speed jet.
Warm motor and running and in gear.
​Can be done not running, results will be close.

​Top of the carb, a slotted screw.
Initial setting is 1 and 1/2 turn out from lightly seated.
As it runs, turn the screw in 1/8th turn and see if it makes any difference in the way it idles.
Repeat this every 10 seconds until the motor stumbles, kicks, stalls.
Then out 1/2 turn.

Important to wait the 10 seconds between turns.
​It allows the motor to burn the fuel in the system at the new rate.

​These motors can run on 1 cyl and run fairly well.
​Do a compression and spark test.

Oh yea, WELCOME!!
 
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