1980 mercury 9.8 poor top end

[wrbea]

this problem is driving me crazy the motor starts great runs up to about mid range with out a problem however it will not plane out a 10 ft zodiac ..i have just sold a older 9.8 that made the same inflatable just fly these are the same motors just 3 years apart and the newer one sucks at high speed ...the only difference is the newer one has a 3 blade prop on it compared to a 2 on the other one ...the motor sounds like it just dosent want to get the high rpms but other wise sounds great

[KURAN]

[wrbea]

hi kuran
thanks for the reply however it was a blank reply
I assume you did not mean for it to be

thanks

wayne

[outboardbarn]

wrbea, Frist thing what year is the engine? and size next u need to to pick up a shop repair book on the engine.
It sound like to me you'er dropping a cylinder. i suggest that u pick up a spark tester at your nearest auto parts store. One that has an adjustable gap, to check the spark. you want to see a nice crisp blue spark in both cylinders.
While the plugs are out take a look at the condistion that the plugs are in. Are they: tanish-brown? black and carboned? maaybe there wet with what looks like a trace of oi on the edge?
after both of thoughs are done give it a compression test. with the plugs out and coils grounded (so u don't wreck the coils) crank the engine threw for a min. of 5 compression cycles. record the reading. Anything above 100 psi. is ok.if there is more than 10% difference between the cylinders then u may want to replace the rings.
if the plugs are wet u maybe running rich. to rich for the voltage to light the fire under compression. or it could come from running to much oil in the fuel mix.

[wrbea]

thanks for the tips ....installed new plugs and plug wires had coils tested and compression is 125 psi in each cyclinder lots of spark but same problem so going to try new gas and tank and switch back to a 2 blade prop and see what happens

[KURAN]

i'am not sure whether the above engine got TRIGGER ASSY on it. the problem seems like the trigger failed to produce high firing output....