Help! No power. Won't build RPMs in gear!!

Joined
Aug 20, 2008
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Most the time I can gather enough information on this great site by just searching. But this time I?m either not typing in the correct words or something.

Here's the question with a little history,

I currently have a 1976 6hp Evinrude model 6604A.

I bought an eleven and a half foot boat, trailer, and motor a year ago from a friend. This motor has been a constant project since I got it. The latest problems came some back. After some diagnosis I found out I was only firing on one cylinder. So to fix that, I have installed a new coil and tune up kit. This included a new set of points, condensers, and such. Got a feeler gauge and set the points at .020 when the flywheel key is in line with the contact point. Then rotate the prop and do the same for the other side. (I?m only adding all of this so the more experienced can correct me if I've done wrong) I also took the carb completely off. I don't think the guy I bought it from ever tuck it off, and this was the cleanest carb I have ever seen. Spotless, there was like one particle the size of a small sand grain in the bottom of the bowl. So was happy about that.

So after all of that finally got the motor purring. All is well. Ran some jugs and honestly for the first time I think it planed out. Pretty stoked! That was last Friday. It was warm here then. That night it got cold and on Saturday my motor barely ran (no power) on the top end. My bulb never got tight; it constantly would die on me. I even swapped spark plugs while I was out there. Still no improvement.

Last night we pulled the flywheel off and checked the points again. They were a little off like .002 or so. Why won't the stay where they were?
So got the points back where they should be and put new hose clamps on the fuel line and took it out again today. Same thing. I can rev it up just fine when it?s in neutral, but when I put a load on it and go forward. It?s almost like its only building half the rpms i use to get. There is brand new fuel in there with the right mix. The only things better now is that the bulb gets hard, and now it won't die.
While I was out there, I tried to figure out if it were sucking air around the carb. I sprayed a little starting fluid on the gasket and it died. I don't think it was sucking there I just think that some got in front of the carb where it sucks air. But still, why would it die with starting fluid and not rev up? I tried that one more time with just a little squirt nothing big at all. What causes this?

Mainly the question is, What needs to happen so a can get power and build rpms when its in gear?

Thank yall in advance.
Jacob
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: Help! No power. Won't build RPMs in gear!!

First things first, and you should already be familiar with this: 1/2 power almost always means it is running on one cylinder. Your coil and points must not be the problem. How about a spark plug wire arcing out where it is clamped to the armature plate? Or how about you have a bad spark plug? Worst case might be a compression problem on one cylinder (blown head gasket).

Anyhoo, as I said, first things first. Check the compression. After you find that is ok, remove and ground one spark plug lead and see how it runs. Then do the same thing with the other one. Chances are it will not make any difference with one grounded and won't run at all with the other one grounded. The one that makes no difference is the one that is not firing. Now find and fix the reason. Don't go off fixing stuff till you zero in on what the problem is.
 
Joined
Aug 20, 2008
Messages
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Re: Help! No power. Won't build RPMs in gear!!

thank you for your help guys, but the first time i had problems and found out it was only on one cylinder. it sounded like crap. even on the low end. But now it will purr right down until i kill it completely. but this last time i went out, i went ahead and pulled the top spark plug boot off and could definatly tell it made a difference. did the same with the bottom boot same results. this was the first time those sparks had been used. so i know its firing on both cylinders. But i guess i will check compression and go from there.

any others ideas?
thanks again
jacob
 

cdoliver

Petty Officer 1st Class
Joined
Mar 18, 2008
Messages
211
Re: Help! No power. Won't build RPMs in gear!!

It sounds like you have spark. If your compression checks out it has to be a dirty carb.
 

Mas

Lieutenant Commander
Joined
Oct 3, 2006
Messages
1,656
Re: Help! No power. Won't build RPMs in gear!!

How far will your spark jump...7/16 with a strong blue arc? Get or make a spark tester and check spark, check compression, and probably rebuild the carb. When was the last time the carb was gone through?

Also, check spark when the motor is cold and warm!

MAS
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: Help! No power. Won't build RPMs in gear!!

Lack of fuel flow will limit rpm under load yet allow full revs in neutral.

Try pumping the primer bulb while under way to see if rpm increases to prove it.

R & R fuel pump and check all fittings to ensure no air leaking into fuel line.
 
Joined
Aug 20, 2008
Messages
13
Re: Help! No power. Won't build RPMs in gear!!

thanks again guys. The carb was completely off and cleaned like a week ago. it was pretty much already spotless when we took it off. and the fuel line from the tank to the motor just got four new hose clamps and will produce a rock solid bulb. so no leaks there. and i've tried squeezing it when when the motor is running and it won't build any more revs. so today i'm going to run a compression test on it.

How many pounds of pressure am i looking for? does 60# sound about right?

thanks again, jacob
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Help! No power. Won't build RPMs in gear!!

three pull of the rope, tell us what you get. are your butterflies horizonal when you move the throttle to wot? could be a link n sinc, problem. spark and carbs not working together.
 
Joined
Aug 20, 2008
Messages
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Re: Help! No power. Won't build RPMs in gear!!

Guys thanks agian for your suggestions and help. I don't know what the deal is. i ran a compression test on it the other day and one cylinder was at 58 and the other 60. Took the boat out again today. A beuatiful warm day. And boat started on the second pull and ran like a top. two guys and some fishin gear and no problem. I unloaded my buddy at the ramp and took it for a spin with just me. This thing is running great now. and i haven't done anything to it since the last time i thought i was having issues. the only difference is the difference in air temperature.

I know this is a stretch, but could air tempertare solely make that big of a difference on this little two stroke? Heavier denser air versus lighter warmer air? I know some two stroke drag four wheeler guys change a lot of there setup on cooler days. but they're running alchohol and crazy stuff.

Don't judge me :confused:
If this is the case, its all good then because it will just be getting warmer outside.

thanks again,
jacob
 

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: Help! No power. Won't build RPMs in gear!!

sometimes they are just freaky.
 
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