70hp VRO won't run once rpms are up

[PeltHunter]

Hey guys I have a 70hp Evinrude VRO I got on a 90 Sea Nymph I bought for early and late season fishing. I got it running by cleaning the carbs and new plugs. Ran it up yesterday and it ran good but the impeller didn't have great flow so I changed that today. Got it all back together today and it doesn't seem to want to stay running under higher rpms sometimes it'll bog out and die when I hit the little throttle lever on the linkage and sometimes I'll put it in gear and let it run up with the butterfly's barely open and it'll go fine then just quit after about a minute. Not really sure what it could be guessing maybe a fuel issue or intermittent spark but I have nobody here to check spark while I turn it over. Any suggestions? I'm not too familiar with outboards and definitely not familiar with these kind of "jetless" carbs (only a pilot jet it seems. It idles fine once you can get it to start back up which could take 30 seconds to a few minutes. Thanks Paul!

 

 

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[180ccf]

Sounds like it is starving for fuel. I am not sure why you say it has no jets, there has to be a few items metering air and fuel. Needle seats and small orifices. Did you change your fuel filter. Check the fuel ball and make sure it is hard and stays hard. If it collapses on itself it is pulling a vacuum and you need to check the fuel tank vent system. If it is starving for fuel it is running lean. The worst thing ever for a two stroke, it can seize up or melt the exhaust side of a piston under a lean condition. When it starts to die and you add choke does it recover or stall out.

 

http://www.crowleymarine.com/johnson-evinrude/parts/47531.cfm?mdl=YZ0APG

http://www.crowleymarine.com/johnson-evinrude/parts/47551.cfm?mdl=YZ0APG

[PeltHunter]

Hey thanks for the info I'm just talking jets in a way I'm used to like a snowmobile or dirt bike. I'll check on the choke thing later on toda


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[fisherdude]

did you ck to see the gas tank vent is open ? 

[finsntins]

are you putting it in gear and using the throttle on the control box to increase rpm's or are you raising the rpm's buy lifting the throttle linkage on the carbs?

[rolmops]

I'm thinking that a 70 horse evinrude vro  is probably late 80s or early 90s. They still used hoses then that were not impervious to alcohol. I would suggest that you replace all the hoses on both sides of the fuel pumps(vro) and check the fuel filters both in the tank and along the lines. If it is a 1980s VRO I would suggest you remove it and either replace it with a past 1991 vro pump or just replace it with a regular fuel pump and mix your own fuel. The early generations of VRO pumps are notorious for failure and destroying engines. If you choose to go with a regular fuel pump you will probably have that engine for the next 30 years.

[PeltHunter]

Both and it cuts out quicker with carb linkage. Is there a nuetral safety on these like the I/Os? I messed with the linkage so thinking maybe that could be it but it was shifting fine


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[finsntins]

when you lift the throttle linkage on the carbs you are not advancing the timing thus flooding the motor.the only way to raise rpm's on a 2-stroke is to do it with the control box throttle.put it in gear and run it as if you were on the water,just dont over rev the motor and make sure no kids or animals are running around.if it still acts up,i would check compression.

[PeltHunter]

Timing should just go off the flywheel no?


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[finsntins]

pm sent

[perchjerk jim]

I had a vro from the early eighties a 50 horse and it ran great woman was warm but once you get cold the alarm would go off. The mechanic told me to put a little gas in with the oil to thin it out. Because the vro stood for very rarely oiled. I opted to mix my gas and oil and run it that way

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[PeltHunter]

Found a bad ground on the back of the shift linkage that would cut out once the linkage moved


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[hard knox]

replace filter and ck fuel pump 

[PeltHunter]

Confirmed spark issue thought I had it pegged took it out for a shakedown and it acted up again spread some wires apart and got it running for a while up on plane. Will have to tear into the wiring deeper tomorrow


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[Gill-T]

Replace fuel lines. Agree with PAP. 

[PeltHunter]

Replaced lines before I ever ran it. I thought I added that I guess not


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[Beanstir]

Keep going. Good luck. i am hoping you find what the problem is. Same problem here. Older 90hp Mercury. Same as you, rpm's cutting back at high speed. I have had fuel pump rebuilt, replaced fuel lines, carburetors rebuilt, replaced 3 coils, sparkplugs and wires, installed new trigger assembly. I thought the trigger assembly would be it.  There was a bad wire on it. Nope same as before, worse could not even get past 7mph. Next is the stator assembly and the switchbox CDI assembly.  Keep this thread going, let us know what solved the problem. Also checked the fuel for water, fuel good. 

[PeltHunter]

Mine doesn't cut back it completely kills the motor unless that is what you mean? I'm going to tear into wires and take the flywheel off and look around under there. When I move around the little timing bracket that goes up under the flywheel is usually when I get spark back and that whole thing moves when throttling up so that may be a good place for you to look.


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[Beanstir]

How are you making out with your motor? We have just today taken my problem motor for a test run after finishing with the fix. Motor middle cylinder not firing properly. Replaced CDI box. Lots of excess gas around lower carburetors. Replaced Reed Set. Adjusted Lever Spark Advance (timing?). Adjusted idle needle. Used fresh gas. Good to go. We did a short test run because of rough water and we were satisfied with the results. Good luck with your motor. Beanstir

[Xxx]

OOHH MAN, those damn CDI boxes can give you a migraine!! One took a partial dump making me guess at a few things, something told me it has to that darn CDI box but being intermittent didn't exactly fit the bill, hooked motor up to the muffs and ran the motor at 3000 rpm you could hear it wasn't nice and smooth and under a load it was way worse, anyway after 5 minutes of a continuous 3000 just shut motor down. Pulled all 4 plugs and the CDI box controlling the plugs that looked darker and not nice lite chocolate color. Changed the CDI box and all's good again. I ended getting the box from a marinea parts place that is right befor T-I Bridge on the left going north on 81, I think it's on the RT "6" side

[PeltHunter]

Loose wire on the timer base I believe is the problem (whenever it dies if I push that wire back up it'll start right back up). Going to test it out with a known good timer base and stator tomorrow to confirm.


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