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1999 50hp model Hshot shaft

gremlinplay

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"Hi all, i have a problem with

"Hi all, i have a problem with a 50hp yammy at high rpm its seems to surge in power and it doesn't sound like its reaching 5000rpm i am guessing it round 4000/4400rpm.almost like its in safe mode! i have cleaned all the carbs,fuel lines.fitted new fuel pump and primer bulb and stil no joy. so i am hoping to have ruled out a fuel problem. i dunno where els to look.
P.S its a hand start motor on a racing duck with a 11 pitch prop on it."
 
just a quick update...
just h


just a quick update...
just had it back on the water to try give a better description of the fault. it sounds like a miss fire at WOT with a definite surge and loss of power. if you back the throttle a bit its clear. but its no where near 5000rpm. took a ride on a mates boat and his motor screams...i am slowly pulling out my hair..the symptom is pointing at fuel but i have replaced almost everything....could it be the CDI? and how can i tell if its running in safe mode?
 
"No tach to be sure of rpm&#39

"No tach to be sure of rpm's? If you are getting up on plane you can't be down more than 1 cylinder if any. Bad coil, plug wire, plug...if only at wot i would look to ignition issues"
 
"Hi Rollie,thanks for your rep

"Hi Rollie,thanks for your reply..yes its only at WOT that it does it...its a strange fault. the previous owner has fitted new coils i see but that not to say one`s not bad either i have put in new plugs that's the first place i looked. could a sensor or a kill switch cause a symptom like this?"
 
is it at all possible timing c

is it at all possible timing could play a role in this surge. i noticed that there is a rheostat on the CDI that obviously advances and retards the timing .there is a single line at the top and double line at the bottom but the metal pointer never lines up with either if u open or close the throttle. i got the story today that the motor went to our local dealer for service and never been rite since which was 9 months back. the owner gave up and sold the boat in the end..now i have the head ache.
 
"Wouldn't be the kill swit

"Wouldn't be the kill switch. Timing could be involved, there are a few possibilities. All hard to diagnose when you can't duplicate it in a shop for a tech. I've been lucky to have a shop that will allow me to borrow used electrical parts to try one at a time on the motor. The right part I buy it, the wrong one..bring it back and try something else. I had a miss/hesitation on my 200hp always at about 3400rpm. Turned out to be a coil going south. Found it by swapping out coils 2 at a time, on the 2nd go the miss went away. Also, go back to the dealer and find out what work he did 9 months ago."
 
"HI there, i went to the so ca

"HI there, i went to the so called dealer and asked what they had done to the motor ,i was taken round the back and showen what all was done
3 X Spark plugs
1 X fuel filter
Gear oil
Flush the Carbs

I will also add i have little faith in the JUNGLE BUNNY mechanic they have there!!
I am gonna try swop out the coils and plug leads see if that makes a diffrence,i will keep you updated with my findings as i go."
 
"No thats sumthing i havent tr

"No thats sumthing i havent tried? how do i go about testing that?
i have also checked the reed valves , they seal and that no tips are curld."
 
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