78 Evinrude-Max Rpm 2500 at W.O.T.?

[Muskab]

78 Evinrude 115 Hp. Recently tore down carbs cleaned and blew out, new plugs, new fuel filter.<br />Idles Fine, Cranks fine. When in neutral motor will get plenty of RPM's while revving up (4500-5000+). BUT when under load and in-drive it won't get past 2500 Rpm. Boat has been sitting for a couple of years. Same prop I had before, and New fuel in tank. Is it possible i'm not getting enough fire and the motor isn't burning all the fuel?? I just cant figure it out..<br /><br />any help is much appreciated!<br /><br />Brian

 

[OBJ]

Re: 78 Evinrude-Max Rpm 2500 at W.O.T.?

Welcome to iboats Brian!<br /><br />We need to determine if all your cylinders are getting spark. Easy to do.<br /><br />Cut the head off a 10penny nail. Stick the nail in one of the spark plug leads. Use insulated pliers and hold the sharp end of the nail about 7/16" from a clean engine ground. Have a helper crank the engine and see if you have spark across the gap. It should be a thick hot spark. Do this for all the cylinders and let us know what ya' come up with.<br /><br />And it would be a good idea to get a compression reading on all cylinders also. The higher the better and they should all be within 10 to 15% of each other psi wise.

 

[Muskab]

Re: 78 Evinrude-Max Rpm 2500 at W.O.T.?

Ok, checked compression all cylinders; all read about 130-135 psi. <br /><br /> Checked spark on all cylinders, all spark well but I think one side of the motor is getting a little weaker spark than the other (like a little bit thinner). Could this be? or am I imagining it?<br /><br />I am the second hand owner of the boat and I noticed the Power pack on the other side (that has the thicker spark) has been replaced before I think because it doesent match the one on the other side.<br /><br /> Any ideas what to check next? Any way to test a Power Pack?<br /><br />Brian

 

[OBJ]

Re: 78 Evinrude-Max Rpm 2500 at W.O.T.?

Swap the power packs around and try the spark test again. If the thready spark follows the older power pack, replace it.

 

[Muskab]

Re: 78 Evinrude-Max Rpm 2500 at W.O.T.?

Changed the old power pack today, put it on the water. Running a little better but still only about 3000Rpm. <br /><br />When I push in the choke for about 2-3 seconds at WOT, motor surges with lots of power and hauls a##. What should I check next? sounds like fuel starvation?

 

[fireman57]

Re: 78 Evinrude-Max Rpm 2500 at W.O.T.?

Sounds like it is time to rebuild or at least clean the carbs.