70hp evinrude power issue

[fishon13]

I have a 1982 70hp evinrude starts every time first crank idles great. Goes to about 2000 rpm then when i try to go to full throttle it bogs down and stalls. sometimes it will go to full power and run great. It seems the problem happens at 3/4 throttle. The in line filter is clean, sparkplugs are pristeen. Two power packs were replaced last year and carborators were rebuilt or cleaned by previous owner. The first time I had the boat out no problems at all. When I got the boat it had old gas in the tank I flushed and put new gas with a 50:1 mix. Any information before I take it to the mechanic would be lots of help. I think it is the carborators.

 

[crxess]

Re: 70hp evinrude power issue

When it bogs down, does the bulb loose prime?(fuel pump)
It you roll the throttle back does it smooth out?(Carb/ignition) Possible float sticking

 

[fishon13]

Re: 70hp evinrude power issue

Thanks the primber bulb does'nt loose prime checked that yesterday. it does smooth out when I back the throtle down. Any ideas on how to issolate which one it might be? If it is a stuck bowl do I have to rebuild?

 

[crxess]

Re: 70hp evinrude power issue

It will take 2 people to check on the water.

USE EXTREME CAUTION!!!

With motor cover off bring mptpr just to point of problem.(bog) Have one person Tap one carb near the float bowl at a time with the plastic end of a screwdriver. If tapping any one carb suddenly corrects the Bog that is the suspect Carb. Pull it and rebuild.

Probably would be prudent tor the cost of kits to just rebuild all 3.

 

[fishon13]

Re: 70hp evinrude power issue

Thanks for the Help I forgot to mention that the motor will throttle up in neutral does this have any influence on the possible stuck float or can it be only sticking under load.

 

[crxess]

Re: 70hp evinrude power issue

No, the motor will react totally different under load.

 

[fishon13]

Re: 70hp evinrude power issue

Thanks again if there are any other things you think I should check I'm headed to the lake (fontana in NC) around noon. I will check before I leave, If it is the carbs any idea on price to fix. most repairs I do myself except carbs long story.

 

[crxess]

Re: 70hp evinrude power issue

Kits are cheap, around $20-$25 per carb on avg. They are not that labor intensive but I have no idea waht a shop might charge.

 

[fishon13]

Re: 70hp evinrude power issue

Thanks for the info will post back after test In the fall how should I put the motor to bed for the winter. I don't want to encounter the same problem next spring. Forgive the ignorance never had to winterize motor orriginally from florida.

 

[fishon13]

Re: 70hp evinrude power issue

well back from the water could'nt reach the carbs very well but did tap them anyone have any other suggestionns

 

[haulyard]

Re: 70hp evinrude power issue

am having same problem with my 1985 70 hp evinrude,mine starts easy but bogs down when advancing throttle , i will run motor about a minute and it will kick in and just about throw me back in my seat ,and will run great about 20-30 seconds then bog again ,i will back off throttle to keep it running then advance again and same thing ... does this sound like carbs or fuel delivery??? vro is disconnected and am running premix...
any ideas?? can someone post a link to carb rebuild kits...or do i need a fuel pump from an earlier year??

 

[scrampbell]

Re: 70hp evinrude power issue

Very similar problem with my 1984 Johnson 70hp Fishon. It idles just fine both in gear and out. It revs just fine on the muffs and in neutral on the water. But under load on the water it won't get past about a fast idle before it bogs. I got the Clymer's shop manual from the library yesterday and will start going through the troubleshooting steps this evening. I'm suspecting the floats, but I will also welcome the excuse to do the link and sync.

Let's keep each other updated here if we learn/fix anything. Good luck!


Haulyard, you can go to shop.evinrude.com, select parts, then choose your motor type from the pull down and select your year and hp on the left. Carb repair kit for my engine is just under $30 each. Not sure if this will fix any float issue though. Anybody know?

 

[egorcenski]

Re: 70hp evinrude power issue

I have the same problem with my 1983 70hp evinirude. It starts just fine on the mufs and pumps plenty of water. It idles nicely and revs up on the muffs too. I put it in the water for the first time this year and she started great and idled well. I got it out on the lake and gave some rpms and it bogged down I went to wot and the boat wouldn't even get up on plane. I have an aluminum center console and that thing should get up to about 25 or so mph, I couldn't even get up to 5 mph. As the motor got up to temp it ran worse and worse to the point where it wouldn't even stay running and it wasvery hard to start. I removed the head to check for bad gasket and such and found the gasket is fine but only one of the three cylinders was firing. I could tell this by how much raw fuel was in two of the cylinders and how dry the third one was. My thought is that I may have a couple of bad coils and really want a turn key motor. My plan is to change all three coils and many other mechanical parts ie. carb kits fuel pump kit head gasket thermostat etc and when finished take it to a shop and just have them tune for link and sink get her running well. I ordered all the parts from iboats and they all came to about 170 with shipping not bad......

 

[haulyard]

Re: 70hp evinrude power issue

hi scrampbell, today i started motor and pulled plug wires one at a time ,top wire pulled seemed to smooth out engine,middle wire stalled engine and bottom plug wire had no effect,So with cover off carbs and engine running i squirted pre-mix into bottom carb and rpm's picked up immediately.
spraying mix into top two carbs stalled engine ,which i assume caused motor to flood ..
i increased motor speed and squirted mix into bottom carb several times until it did what i was hoping for , cleared up and ran smoothly (without squirting mix)....shut motor down and started again and had to do the squirts all over again,maybe on the river i can run her long enough to clear things up,but i know there may be no way around a future carb re-build, but things are looking promising...........

 

[haulyard]

Re: 70hp evinrude power issue

egor,try squirting the premix into your carbs ,is worth a try,carb kits cheaper than anything else...

 

[krogie]

Re: 70hp evinrude power issue

when you said you replaced the powerpacks ( plural ) did you mean the coils?

 

[Randybeall]

Re: 70hp evinrude power issue

Squirting pre mix is a good test under load, however, do not run it long periods trying to "clear it out"! The two stroke engine depends on proper fuel mix from the carbs at all times to lubricate bearings, pistons, and rings. Partially plugged carbs have likely killed more engines from burned up parts than any other reason. Print out the carb overhaul instruction sticky and overhaul them. It is not a black art or big secret. I have been doing carbs since the early 60s on cars trucks boats and motorcycles, they are simple if you organize what your doing.

 

[bill_sss2002]

Re: 70hp evinrude power issue

Squirting pre mix is a good test under load, however, do not run it long periods trying to "clear it out"! The two stroke engine depends on proper fuel mix from the carbs at all times to lubricate bearings, pistons, and rings. Partially plugged carbs have likely killed more engines from burned up parts than any other reason. Print out the carb overhaul instruction sticky and overhaul them. It is not a black art or big secret. I have been doing carbs since the early 60s on cars trucks boats and motorcycles, they are simple if you organize what your doing.

I have a 1971 evinrude 50 on a 16' boat which when I put it into drive and give it full throttle I get about half of the rpm's as when it is in nuetral why? All this is happening while in the water.

 

[krogie]

Re: 70hp evinrude power issue

yes , get the proper manuel for this motor for sure , it is the best thing you can do for yorself and the engine. as for the carbs it never hurts to give them a good cleaning and inspection , so even if this is not your problem there was no work done in vain. it sure beats burning up a good motor over something so small .

 

[scrampbell]

Re: 70hp evinrude power issue

I fixed the issue on my 1984 70hp Johnson!

As per the Clymer's manual suggestion, I started at the fuel tank and worked my way back. Main line 5/16" hose was starting to crack, especially at the fuel pump. Also, with the engine running, fuel was pouring out of one of the T connections that feeds fuel from the fuel pump to the carbs. So, I also replaced the 5/32" hose and the two small T connections in that fuel line assembly. I used standard duty nylon cable ties as hose clamps on the 5/32" hose (I know this is not ideal, but the best I could find).

Also, while I was at the mechanic's buying the 5/32 hose and T-connections, he was pretty confident that this wouldn't fix my "Won't go fast" issue, as he put it.

So, since I already had the silencer plate removed to visually check if all butterfly's were opened at the same time and because of the mechanic's advice I removed the top cylinder high speed jet (Float Bowl Orifice Plug on shop.evinrude.com) with my skinniest screwdriver (I could see down the hole with a flashlight). The nozzle on the orifice plug was very gummed up and I couldn't see through it at all. After cleaning this one and the middle carb the same way, I just gently poked my cleaning tool into the bottom cylinder orifice since it would have been much more difficult to get it out of the carb.

Took her out yesterday after work and she ran like a champ!

To summarize, what I did to fix the issue and how long it took (Keep in mind that I'm no veteran):
1. Removed Silencer plate assembly to visually check that all butterflies were open at the same time (20 minutes)
2. Replaced most fuel line from tank to carbs (1 hour 15 minutes - does not include finding parts... 5/32" hose was hard to find on the weekend)
3. Cleaned float bowl Orifice Plugs, aka High Speed Jets, on all 3 cylinders (20 minutes). I didn't test on the water after replacing the fuel line, but I'm pretty sure that #3 was the main cause of my problem.

Good luck to you all and I hope to hear soon that yours are also running like new again!