Rough accelleration

TinBoats.net

Help Support TinBoats.net:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Charger25

Well-known member
Joined
Jul 31, 2012
Messages
457
Reaction score
0
Location
Aylett,Va.
Got a slight problem with a buds early 90's 25hp evinrude. It starts up great with an occasional lean pop when cold. It idles well and top end is good. The issue is the bottom 1/3 of the throttle, what I mean is when accelerating to get on plane it stumbles / struggles to get up on plane. Once up it runs great,you can back off to 2/3 throttle and it still runs good .
What I've done is pull carb and it is clean, can't find any debris anywhere ,needle and seat looks good, float is level bottom of carb.
checked plugs and gap, even put in a spare set I had. For the heck of it ,ohm out coils .both were the same, coil wires were good as well. No fuel restrictions anywhere, new line and bulb . link n sync appear to be ok. I'm at a loss as to why it struggles to get up on top end. Any advise is welcome. Oh and it does not have a T-stat in.
 
Without a thermostat the motor may not reach operating temperature, causing the rough running. Why is the thermostat out? Maybe to compensate for a weak water pump? Maybe corrosion in the water jackets if it's a salt water motor? If it's been awhile, it may be time for a head gasket.
 
Did you pull out the little lead shot where the adjustment needle is and clean in there. The very narrow passages are easily blocked
 
Use Champion spark plugs.
Make sure the engine is warming up at idle
Take a look at the pick up point of the throttle roller to the mag plate. Pick up the carb earlier. Make sure it is getting to WOT as well.
Lean the engine at idle somewhat if you think it is rough/rich.
Replace the High speed jet with a new one. Have seen several HS jets eroded several sizes larger than stamped. Probably around 100 jets or so in the last year.
Take a look at the prop. Correct pitch? Worn? Less pitch and or a worn prop will not load the engine enough to make it 2-cycle during acceleration.
That should give some ideas....now go fix it.
 
Nohasslekindaguy , he took the T-Stat out,cause it got stuck and over heated . I had the head milled and installed a new gasket. This was several years ago. it could use a new impeller, It is run in salt water at times but always flushed afterwards.

JMichael, Its a 2stroke E25REND link and sync "appear'' to be ok. Didn't look at it that closely


Analog Kid, didn't have any lead shot to replace with ,so didn't pull those out.


Pappy, it is running Champion plugs, JY77 ,? Its as warm as it can get w/out a t-stat, It is getting to WOT as butterfly is open all the way, I think I have a spare HS jet in my parts box
Didn't look at the pick up point on mag plate, Prop is 10 X 13 but well worn , could use a new one.

Thanks Fellas, going it look at it this weekend. If ya can think of anything else............
 
Think I got it figured out , It seemed that the timing plate was sticking kinda. There's a small coil spring that advances the plate, after running it with the hood off ,I saw it slam forward after a few seconds or so after he nailed it to get up on plane. I'm guessing that and some plugs that needed cleaning or replacing is all it was. Thanks Fellas, Oh and Pappy the plugs are L77JC4 Champions.
 

Latest posts

Top