1977 70Hp Evinrude boging down.

[huck42]

Hello, first time poster, long time reader. I have a 70hp Evinrude model 70773S. It idles fine, but bogs down under a load when you try to open up throttle. I cleaned the carbs three times, relaced fuel pump, replaced water pump, put in new plugs. You can raise the warm up leaver and get the rpm up to 2500 and it will run fine until you kill it and you have to start over.
The compression on #1 is 115, #2 is 110, and #3 is 115.
It has just started this and is getting worse.

 

[xtraham]

Re: 1977 70Hp Evinrude boging down.

classic symtems for these engines, did you soak the carbs in carb cleaner and remove the welch plugs and clean the ofiices with compressed air? also check the bottom carb. the air silencer will pinch off the fuel line to the carb. runs fine util its under load right? also look for cracked coils and check spark 3 cyl's idle good on 2 pull each plug wire 1 at a time see if rpm's drop if not that is the cyl with fuel/fire problem

 

[huck42]

Re: 1977 70Hp Evinrude boging down.

I let the carbs soak overnight and cleaned them with compressed air. I did not pull the plugs on the carbs!
There is good fire on all 3 spark plugs! When you pull the plug wires one at a time it changes the rpm's.The air silencer is not on it now. It acts like it's flooding i have it in a drum of water and after you shut it off there is some gas and oil on top of the water. When you raise the warm up lever it takes a little while for it to raise the rpm's.

 

[rickdb1boat]

Re: 1977 70Hp Evinrude boging down.

2 things I would do right off. Take a timing light and a helper with you on the water and hook it up to each plug wire when under a load and bogging down. See if you are losing spark under load. The other is pump the primer bulb and see if she picks up. I know you replaced the fuel pump, but ya never know. Check for air leaks and fuel leaks at all fuel lines from the tank right up to the carbs. Make sure they are all tight and secured. A small air leak will cause those symptoms...What do the spark plugs look like right after this happen? Fouled, dry, Etc....Pull them and see the next time it does this....

 

[huck42]

Re: 1977 70Hp Evinrude boging down.

Rick I went to the lake friday night and I didn't have a timing light but I got my friend to drive and I pulled the plug wires one at a time with a pair of plyers that had a hole in the insulation. So I'm pretty sure they are firing. I pumped the primer bulb and it didn't help. The plugs are kind of black and wet. All hoses are new with new clamps.

Thanks

 

[xtraham]

Re: 1977 70Hp Evinrude boging down.

even though it shocked you, you have to make sure that the spark will jump at least 3/8"

http://www.outboardrepairs.com/johnson_outboards_by_horse_power/?johnson#johnson_70_hp

 

[huck42]

Re: 1977 70Hp Evinrude boging down.

I don't know if this has anything to do with it but with it idling in the drum I can put my hand over the carbs starting with #1. It will kill the engine, same thing with #2 but #3 just changes the rpm's a little and I have alot of gas on my hand. #2 and #3 don't do this. I swaped coils on #2 and #3 it still does the same thing.

Thanks

 

[xtraham]

Re: 1977 70Hp Evinrude boging down.

carb. starving, it's always the one thats hard to get too..open the throttle look in the throat above the butter fly and clean the 3 holes that are there with a piece of stiff wire remove the screw in plug at the top front spray carb cleaner then air replace the plug sometimes that will get, it if not remove the carb again remove the plugs and clean it really good. install a new carb kit...

 

[huck42]

Re: 1977 70Hp Evinrude boging down.

I took my boat to the lake this weekend after I cleaned and put new kits in the carb’s it run a little better but still not right. After we got it home I pulled the plugs #2 had water on it. I pulled the head but could not find a leak on the gasket would it be obvious. Or do I need to look some where else? There was some water in the exhaust port and on top of the head.
Thanks

 

[guywithboat]

Re: 1977 70Hp Evinrude boging down.

Make sure that you are getting spark to all the plugs. At this point you may have a dead cylinder. I had the same issue with my 72 Evinrude. I had to replace the power pack.

 

[blazzer00]

Re: 1977 70Hp Evinrude boging down.

I have this same engine with the same problem. I found that if I primed it when it starts to bogg it pick up idel and takes off. If I dont prime it the motor will die if I dont take it out of gear! Any advice on this problem. Im going to replace plugs.