1975 70hp Evinrude has no power in the water

I bought a little bass boat over the winter, and it has a 1975 70hp Evinrude on it. I changed out the fuel in the tank, and drained all the lines and bowls. Put it on the water hose and it fired up great in the driveway, but it won't run in the lake. I sprayed carb cleaner in the carbs and took a small tooth brush to them. Then I could get it to idle in the lake, but it sounds very weak and can't handle the load of going into gear. It sound like it is flooding. It gets a real hollow sound and slows to a stop. I let it idle through 4 gallons of fuel with Sea Foam with no improvment.
I then took it home, checked the compression, and it has 118psi, 118psi, and 120psi. I checked the spark with an ignition spark tool, and all three have strong spark. I then let it idel in the driveway and pumped the primer bulb. There was no change in the idle. While it was still idling I pulled the plug wires one at a time. The #1 cyl showed no difference in the idle. The #2 caused it to run very rough and blew out a lot of white smoke when the plug was reattached. The #3 caused it to change a little, but also blew out a lot of white smoke when reattached. This leads me to believe that I have a fuel problem on #1 and possibly #3.
I then pulled the carbs and cleaned them. All of the passages seemed to have very good flow with no observed obstructions. It was dark by the time I was done tonight so I didn't get to the lake. I will test it tomorrow after work. Is there anything else that anyone can think of that I may have overlooked? Any help would be greatly appreciated. I have a fishing tourny on Sunday, and I really don't want to fight the wind in the pantoon boat again. Thanks.

Re: 1975 70hp Evinrude has no power in the water

Others with more experience will chime in but it sounds like #1 cylinder is either not firing under compression or it's not getting fuel to fire. Did #1 have a snap and bright blue streak to it?.

Re: 1975 70hp Evinrude has no power in the water

Pull out numer 1 plug and see if it looks like the other 2. If it does you may need a link and sync or a carb rebuild.

Re: 1975 70hp Evinrude has no power in the water

Will, yes it was very nice. Like a Tazer going off.

Patrick, I will double check when I get off work, but I'm almos positive that they all look about the same. Pretty clean, and just a touch damp.

Re: 1975 70hp Evinrude has no power in the water

Will, about the spark test. My spark tester shows that for a .030 plug gap it should be set at almost 3/4 of an inch, but I have read in several places on this forum that it should be able to arc a 7/16 gap. Is it different for a two stroke mixture vs. gas? I get an arc for over 1/2" but not the 3/4" my tester says it should be for a .030 spark plug.

Re: 1975 70hp Evinrude has no power in the water

Okay, I tested it on the water again this evening. I had a little improvment, but not engough to count for anything. I put in a new set of spark plugs just before going to the lake. When I got back I checked the plugs. #1 was wet around the electrode and the ceramic at the base of the electrode. #2 was dry except for the ring near the threads. #3 was wet in the same areas as #1, but not quite as bad. I also looked inside the spark plug holes and saw that the #1 an #3 pistons looked pretty wet. The #2 just looked lubricated. I know that if there is fuel built up in the cylinder then it is usually a spark problem, but could it be that it's running too lean to burn?

Re: 1975 70hp Evinrude has no power in the water

Okay, I tested it on the water again this evening. I had a little improvment, but not engough to count for anything. I put in a new set of spark plugs just before going to the lake. When I got back I checked the plugs. #1 was wet around the electrode and the ceramic at the base of the electrode. #2 was dry except for the ring near the threads. #3 was wet in the same areas as #1, but not quite as bad. I also looked inside the spark plug holes and saw that the #1 an #3 pistons looked pretty wet. The #2 just looked lubricated. I know that if there is fuel built up in the cylinder then it is usually a spark problem, but could it be that it's running too lean to burn?

Re: 1975 70hp Evinrude has no power in the water

This motor is a 70573E, if that helps any.

Re: 1975 70hp Evinrude has no power in the water

I always say if I kit one carb,may as well do all 3,when installing start readjustments at the midcarb,Clean all 3 twice,make double sure hispeed set orfices are cleaned,set 3 lowspeeds at 1 1/2 turns out,mid carb start fine low adjustment.look in secret files.

Re: 1975 70hp Evinrude has no power in the water

My vote is carbs....did you actually put kits into them?....and pop the welch plugs and clean the channels behind them?
If not, I know where I'd start....

Re: 1975 70hp Evinrude has no power in the water

No, I didn't put kits in. I just disassembled, cleaned, and inspected. The carbs looked good other than a llittle gunk build up.
This morming I found a couple of corroded wires that were split. One was the red lead to the rectifier, and other was the red battery lead on the same bus. I went through the whole wiring harness, but didn't find anything else. I fixed the ones I found. I ran it on the muffs for a bit. Now cly #2 and #3 are both running strong, but #1 still has nothing. I pulled the spark plug on #1, and it is wet, and the cylinder has a good bit of fuel in it. The piston head was very wet. It keeps passing the spark thest all the way out to 5/8", and that is more than the 7/16" this forum says, and more than the 1/2" my book says. So I should have spark, and I can see the fuel in there, but still no bang. It has got to be something little that I am overlooking.

Re: 1975 70hp Evinrude has no power in the water

A little gunk in a carb means alot! I dont believe the rectifier has much to do woth your spark,but if you have good spark the next step is fuel.Air,fuel,spark thats it.

Re: 1975 70hp Evinrude has no power in the water

You should be right about the rectifier. I believe it only deals with the charging system. The wet cylinder is what is throwing me off. I'm going to pull the #1 carb again, and give it another go. Something is just not adding up in my head. Maybe I'm just over thinking it.

Re: 1975 70hp Evinrude has no power in the water

Okay. Disasembled and cleaned #1 carb again. Still same thing. It's not firing on the #1 cylinder, and it has plenty of raw fuel in the cylinder after running. I even ran it with the spark tester on to see if it may be loosing spark while it is running. It had lots of pretty blue spark. Could something be causing it to spark at the wrong time on just that cylinder?

Re: 1975 70hp Evinrude has no power in the water

Did you remove and clean main jets? Unhook top carb choke link & close, open choke listen for change. A bad top crank seal will effect top cyl. Remove main jet plug & pump bulb ck fuel flow, plug back in do center & compare. A lean cyl at low rpm won't burn right and can look wet. All else fails swap top and bottom carb's.

Re: 1975 70hp Evinrude has no power in the water

Big Flop, I did the choke on the #1 carb like you said, and it slowed the motor, and produced more wihite smoke. I will have to try the other things tomorrow, I have to get ready for our fishing tourny now. Looks like another day of fighting 25-35mph winds in the pontoon boat. Yippie! :facepalm:

Re: 1975 70hp Evinrude has no power in the water

BomerFett said:

No, I didn't put kits in. I just disassembled, cleaned, and inspected. The carbs looked good other than a llittle gunk build up.
This morming I found a couple of corroded wires that were split. One was the red lead to the rectifier, and other was the red battery lead on the same bus. I went through the whole wiring harness, but didn't find anything else. I fixed the ones I found. I ran it on the muffs for a bit. Now cly #2 and #3 are both running strong, but #1 still has nothing. I pulled the spark plug on #1, and it is wet, and the cylinder has a good bit of fuel in it. The piston head was very wet. It keeps passing the spark thest all the way out to 5/8", and that is more than the 7/16" this forum says, and more than the 1/2" my book says. So I should have spark, and I can see the fuel in there, but still no bang. It has got to be something little that I am overlooking.

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If there was gunk in the carburetors, and you did not buy kits, how did you R&R the welch plugs? Or did you?...you never did answer that question.
You have to remove them to verify that the channels behind them are not plugged, and there is no other way to access them.

Tim Frank said:

My vote is carbs....did you actually put kits into them?.... and pop the welch plugs and clean the channels behind them?
If not, I know where I'd start... .

Click to expand...

Re: 1975 70hp Evinrude has no power in the water

Tim, I did not remove the wech plugs. I removed the carbs from the motor. Then I removed the high and low speed plugs, float bowl, float and float needle. The only parts that were relpaced were the gaskets. I didn't go any further than that. Mainly because I am still studying up on how to go any further with these carbs. There doesn't seem to be much to them so I'm sure there isn't much room for error when putting them back together. Looks like a full rebuild is in order, including welch plugs. I should have it figured out by the time the kits come in.

Re: 1975 70hp Evinrude has no power in the water

Well, it looks like I have taken too long to finish this fix. My wife says that it is going into the shop in the morning. I guess I can't complain about a wife that wants to go fishing. I will post the results when I get it back, but I'm sure y'all are right about it being the carbs. If I would have known what I know now then maybe I could have tore them down all the way the first time, and maybe even got them back together right.

Re: 1975 70hp Evinrude has no power in the water

My wife dropped off the boat today. The guy pulled the #1 plug and said, you've got a blown head gasket. Then explained that the cylinder was getting water in it, and that was why it wasn't firing. Apparently he knew this because the inside of the cylinder was very clean. I gues that would explain why it was always wet inside after I ran it. He is going to call later to let me know if it is even worth fixing. It was run in salt water before I bought it, and he said that often leads to more problems that wouldn't be worth correcting.