68 evinrude 40hp won't plane out boat

[hokie60]

i have a 68 evinrude 40 hp on a '65 15.5 ft seaeray 500
runs great at slow speed but will not plane out .
the model is 40873A and the serial is EO4702
boat mainly used for pulling tubers thanks

 

[Solittle]

Re: 68 evinrude 40hp won't plane out boat

What troubleshooting have you done so far? Gotta start somewhere.

 

[hokie60]

Re: 68 evinrude 40hp won't plane out boat

i've changed plugs, cleaned carb, changed prop
maybe there is a adjustment i missed

 

[Paul Moir]

Re: 68 evinrude 40hp won't plane out boat

Perhaps you're dropping a cylinder. Is it only turning about 1/2 the normal RPMs? If so try a spark test with a gap of 3/8". This can be accomplished with a cheap spark gap tester or with a pair of nails pounded into a board 3/8" apart ; one connected with a length of wire to the engine block and the spark plug boot placed over the other.

There's a familiar problem of cracked ignition coils which will allow the spark to jump a little but not over about 1/8". This causes both cylinders to fire at idle, but one to drop out as the RPMs come up.

 

[hokie60]

Re: 68 evinrude 40hp won't plane out boat

i just did the 3/8" test and the spark jumped the
distance could it still be the coils or maybe a fuel problem.

 

[Paul Moir]

Re: 68 evinrude 40hp won't plane out boat

Definitely not the coils then, or the points/condensors. That's a healthy ignition system.

Have you run a compression test?

 

[hokie60]

Re: 68 evinrude 40hp won't plane out boat

yes it has about 100psi per cylinder

 

[rickdb1boat]

Re: 68 evinrude 40hp won't plane out boat

I had this problem on my 1991 70 HP rude and as Paul said, the coils could be a problem. Mine too hit on all 3 during the spark test and at idle. But on the water under a load, one was shutting down on me. 3 new coils and all is well. Not saying that is the problem with yours, but it can happen...Hook up a timing light to each plug wire while on the water when this happens. This will verify if you are losing spark or not...You may also have a failing fuel pump. Have you tried squeezing the primer bulb and see if she picks up? Give that a try too...Did this happen suddenly or is this an ongoing problem?

 

[hokie60]

Re: 68 evinrude 40hp won't plane out boat

this has been doing this from the day o bought it three weeks ago. i will try the timing light and let you know
and also squezzing the bulb.