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Charles
Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3343
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have a 25 hp 2 stroke 1994 yamaha. It is on a 13 ft skiff. used to plane out easily and

Customer Question

i have a 25 hp 2 stroke 1994 yamaha. It is on a 13 ft skiff. used to plane out easily and haul butt, it will not plane out now. it idles smooth, i have new gas, has 120 psi both cyliders
Submitted: 1 year ago.
Category: Boat
Expert:  Charles replied 1 year ago.
Hello, my name is***** you for allowing me to assist you today.
Would you please post the model number of the engine?
Customer: replied 1 year ago.
Yamaha C25 ELRR
Expert:  Charles replied 1 year ago.
Thanks, ***** ***** engine been sitting for some time unused?
Customer: replied 1 year ago.
no i use it all the time.
Expert:  Charles replied 1 year ago.
How long has the engine been running this way?Have you checked the fuel filter for water?How do the spark plugs look?Have you checked for spark on both cylinders?
Customer: replied 1 year ago.
i will do that now
been a few months i usually just cruise around the inlets slow , a few monthds ago i went to go plane and it wouldnt quite make it. just barely
Expert:  Charles replied 1 year ago.
Ok, First remove the plugs and look at the tips. If you have a multi-meter, you can test them.Then using an adjustable gap spark tester, check the spark on the engine. Make sure that both cylinders are hot and blue spark. The fuel filter can be unspun and then the contents poured into a glass jar. Make sure that there is not two layers inside the jar.
Customer: replied 1 year ago.
k ill be back in 10 mins
Expert:  Charles replied 1 year ago.
Ok i will be here.
Customer: replied 1 year ago.
what would a weak spark cause it to do ?
Expert:  Charles replied 1 year ago.
Run poorly on both cylinders. that an be caused by a weak stator, pulser coil or the CDI.
Customer: replied 1 year ago.
well, i took each plug out and tried to use this hei spark tester i goy from advance auto https://www.youtube.com/watch?v=9Vl9JlIFiicIt didnt show a spark. def not a fat blue spark. i am sitting in the water in blazing sun though.So i pulled both plugs and tried to run the engine on one cylinder . it didnt like that . it tried . i tried using a screwdriver from the lead to the block. if there was a spark it was faint. i put both plugs back in. it starts right up idles great. i used the fast idle on the throttle it revs great.I pulled the filter. there is a very slight amount of possible water . but i mean a tiny bit of separation/bubblesIm gonna take it out bumble around and fish and maybe try some more tommorrow... i just dont get it . 125 psi...gas. spark . what tha heck does it want
Expert:  Charles replied 1 year ago.
Does the issue happen more after you have been running for some time?
Customer: replied 1 year ago.
theres no "issue" it just not enough power to plane out.
Expert:  Charles replied 1 year ago.
I guess, what I am asking, is that does it always happen or just after you have been running for some time?
Customer: replied 1 year ago.
well i have a no wake zone for the first 20 mins ....soooo ... ill have to take it out. let it sit i guess...whille im out there and try to take off
Expert:  Charles replied 1 year ago.
I am just wondering if it is getting hot and that is the issue. Can you feel the water discharge from the engine next time that you have it out. A hot engine will not run well either.
Customer: replied 1 year ago.
I will follow up this week. its the same. weird .Compression . check
Gas filter . check
Boat bottom clean. check
Idles smooth. check
fuel line vented. checknew plugs ? but it idles smooth
valves ?
carb jets ?
seems to throttle up when not under load
replaced prop with new prop. supposedly with the same pitch etc. took old prop to a well known prop shop in town . murphys .
Expert:  Charles replied 1 year ago.
Did the motor plane out with the old prop?
Customer: replied 1 year ago.
Yes
Expert:  Charles replied 1 year ago.
What markings are on this old and the new prop?

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