performance issue/ '86 "25 sj"

[hootiesskipper]

'pull starts on 2nd pull EVERY time and idles perfect, even when u shift into gear, runs GOOD thru half to 3/4 throttle, then when u go on to full throttle, there is no more power. It just plows and labors as if the prop is WAY to stiff, or there is too much weight to handle, UNTIL you kink the fuel hose to starve it for fuel, (lean way out), and it will pick up and run like a SCAAAAALDED ape, then let fuel line open and it will continue to RUN until you have to back off throttle, then its the same sequence all over. I ORDERED 2 DIFFERENT part #'s of pilot jets, no change. what's been done: compression ck @135# and 140#'s; disassembled (x3), soaked in carb cleaner 1st time, CLEANED EVERY vein w/90#s air nozzle, renewed kit, and float, (TO SPECS), ran it, no change, tore down twice more to renew pilot jets, pulled reed plate and checked, no leakage, ran it again with no change. All this was after purchasing a NEW tank, hose assy., and non-eth. premium fuel. I am wondering if the main jet has been enlarged in an idiot attempt to gain more power. It sits on a 14' long and 6' WIDE, mon ark alum. hull with nothing but 2 seats, paddle, and fuel tank. NO added wt. VERY light boat, and as said above, it WILL haul tail when it does stretch out upon setting up a lean condition. THANK U for any ideas, have a blessed day!

[99yam40]

I would monitor the timing to make sure it is advancing properly just to make sure. Not advancing (less power)


I found the main jets in my C40 were drilled out by previous owner. Took me a year to finally get that found out. Never did find the correct way to measure on the net.
I finally bought one and compared the holes using small drill bits, then bought all new ones when I saw them too big compared to the new one.

My motor would run well with cowling and silencer off and running into the wind, but would drop a cylinder at high RPM going with the wind or with all parts in place.

Might look at fuel pump to make sure it is not leaking into crankcase and causing too rich of a mix in one cylinder

[hootiesskipper]

25sj performance issue

First off let me thank you for response. How can one tell if the pump is lkg.? And did the c40 true up w/smaller jets? Thanks again. Jeff

[whsalum1]

I have a 2008 25hp doing basically the same thing.Did you ever get this fixed ??