1970 40hp evinrude big twin "bogging down"

[aludeidmonkey]

Hello,<br /> I have a 1970 40hp evinrude big twin with a power loss problem. The problem was extreme at idle and power but after replacing plugs and rebuilding the carb., it only does it past half throttle in gear. I also bought a new fuel line bulb and gas tank w/ vent. I had the engine making all rpms before I replaced the fuel tank. The bulb would lose pressure and as soon as I would pump the bulb the engine would open up for a second. Now it will only hang at about 60% of its max power and the bulb stays firm. I took the only fuel filter I saw apart and it was clean and also took the pump apart and it appeared to be fine also. Should I replace the parts inside the pump anyway? Also, in idle it will rev as high as the cutout safety switch will allow. Only problems are when a load is applied. <br /> Thanx in advance

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

Reving it in neutral won't tell you anything and may blow it up or damage it (if you haven't already). The engine has to be under load to tell if its operating correctly.<br />If you have the fuel pump apart replace the parts, as it sounds like at one point you had the symtoms of a bad fuel pump. Check all your fuel line connectors for air leaks. You bought new hoses, did you buy new connectors also? What did you do to the carbs when you "rebuilt them"?<br />Have you done a compression test, if so what are the numbers?

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

The only things I have done to the engine I posted. As far as blowing the engine I have worked on enough things and ran enough boats to know when I should back off. Any suggestions??????

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

Exactly what did you do to the carb when you rebuilt it?

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

I vatted the carb body and harware. I also replaced the float, pin, needle, seat, all gaskets, and ceaned the jet. The carb is immaculate. It is appearing to get too much fuel now. How can I test the engine to see if it is getting too much or too little fuel?

 

[united jigsticker]

Re: 1970 40hp evinrude big twin "bogging down"

turn your idle screws in while @ idle.

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

Where are they at? The only things I see are mixture adjustments.

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

Put 2 fingers in the throat of a carb, if it gets worse that carb is probably running rich, if it gets better it is too lean. Stop the engine while its running at the rpm that gives you trouble. Examine the plugs, black sooty equals rich, brown equal good, grayish white equals lean.

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

The mixture adjustments would be for the idle mixture. How many turns out from lightly seated are they.

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

The low end adj. is about 1-1.5 turns out when idling best. When I do the finger test it dies down.

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

Does that engine have 1 or 2 carbs?

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

one carb

 

[jim dozier]

Re: 1970 40hp evinrude big twin "bogging down"

With one carb, if the plugs don't look the same its not the carb. Either, compression, ignition, or reeds need to be looked at.

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

I just put a fuel pump kit on it and now it runs out of the water like a champ. I got it idling better than any other motor I have heard but, the plugs are different as far as getting carbon build up. I also did a compression check and both cylinders were between 90 and 95. I haven't put it in the water and ran it under a load yet but, do you think I have an ignition problem?

 

[aludeidmonkey]

Re: 1970 40hp evinrude big twin "bogging down"

Just for future problems like this one, I finally broke down and pulled the flywheel. It revealed the entire problem. Both coil pack ground wires had been chaffing on the drive shaft. There was only one strand holding on the first one and half on the other one. Thanks for all the help.<br /> Charles Brackett