mercury 1988 3 cyl 70 hp

[Simmity]

Hi Guys,
Hope you guys have some input for me, if so thanks.

The problem I'm having is, when on the water, the boat will do 3500 rpm. On occasion when I throttle down to a low speed, the rpm drops, but, when I throttle up it wont go past 1300 rpm. Then, If I throttle up and down a few times, it goes back to working normal. Happens periodically.
Compression is 120 psi on all 3 cyl. cleaned carbs. Any recommendations?

could it be a bad coil? or timing?

Thanks

 

[flyingscott]

3500 rpm is to low. Have you tried pumping the primer ball? Have you done a compression and spark test?

 

[Simmity]

sorry, meant 4500 rpm
put, new water pump
yes, I tried pumping the primer ball
I did compression test, 120 psi on all 3 cylinders
changed plugs,
not sure how to do a spark test.

 

[flyingscott]

4500 rpm is still to low. To do a spark test buy a cheap spark tester and make sure the spark jumps at least a 1/2 " air gap.

 

[Simmity]

whats a normal rpm?

 

[flyingscott]

I believe that motor should go to 5500 rpm.