Evinrude 70hp bogging down when throttled up

[hv]

I have a 1982 Evinrude 70hp 3 cylinder 2 stroke engine on a boat that I fixed up with my kids. It was running OK last summer but could not pull a skier, seemed to bog down under load. It would run fine (pushed the little 15' boat at 32mph), but not when under greater load like pulling a skier. I assumed it was a fuel problem and removed all three carbs and cleaned them, replacing the gaskets between the bowl and body. I made sure the floats were set right as per manual. The needles looked fine to me. I did not replace anything else. I also looked over the pump and noticed the screen was caught in the gasket - so fixed that. The rest of the pump looked OK to me, so did nothing to it. It starts great, and idles fine.

However, now it will not even get to WOT. Just chugs along at 8mph. If you push the throttle lever forward it stalls the engine. Not getting enough fuel?? The bulb stays firm all the time. I tried squeezing it when on the go, but made no difference.

I also replaced the spark plugs - no difference.

Not sure where to go from here. It was working better before I cleaned the carbs and looked opened the pump.

any advice welcome.
thanks

 

[racerone]

2 tests to do.------Post the results of a compression test.------And see if spark jumps a gap of 3/8" ( 1 cm ) or more.----Post results of proper testing.----Sounds like the motor is running on 2 of 3 cylinders.

 

[boobie]

Do a cylinder drop test on it. May tell you more.

 

[hv]

sorry, forgot to add. I did a compression test and got 120psi on all three cylinders. I also used a spark tester and got a spark at each plug, but not a gap tester. I will have to buy a proper gap tester and try it.
What's a cylinder drop test?

 

[racerone]

Start motor.----Let it idle.----Pull one sparkplug wire off at a time.-----Report on how the motor reacts when you pull the wire off.-----Report on how the motor reacts when you put the wire back on.

 

[hv]

OK I'll try that. I assume that can be done on muffs? or does it have to be in the water?

 

[boobie]

Can be done on muffs. That's the cyl drop test.

 

[hv]

Results from the 2 tests:

Cylinder drop test
Started the engine and once idling, pulled the wires off one at a time, replacing them before pulling off the next.
Top wire off - the engine died immediately
Middle wire off - no change to engine sound or function
Bottom wire off - slight change in sound, but engine did not die, when replaced engine sounded stronger again.

Spark gap test:
Set gap of tester to 7/16" and tested all three wires to plugs, all three had sparks continuously jumping gap while engine ran. When testing the top wire, the engine never started, but still showed good spark - I guess that was to be expected given the results of the drop test.

So where do I go from here?

thanks for the help.

 

[racerone]

Some will argue ---I would clean the carburetors.----Sounds like high speed jets in carburetors might be restricted.----They are in the float bowl and often missed by a novice.-----And do NOT RUN this motor until you find the issue.----No fuel going into 1 cylinder means no oil.------Could also be water spraying in from faulty exhaust manifold gaskets.----Also a common issue on a 40 year old motor !

 

[hv]

I was thinking fuel too, so I cleaned the carbs again, just a few days go. Is there any particular way to clean them? not sure what I missed. was there something I needed to remove and clean properly? there is a tube going into the bowl through the middle of the float, but I blew air and carb cleaner thru and it seemed clean.

here is the link to the carb I have. also gives the engine model #

http://www.marineengine.com/parts/j...LCNB&manufacturer=Evinrude&section=Carburetor

I attached a diagram from the manual too.

 

[hv]

seemed the link didn't work - sorry
my engine is a 1982 Evinrude 70 hp E70ELCNB

I use marineengine.com for parts

 

[racerone]

That tube is called a nozzle.----Remove drain plug on the carburetor bowl.----Then look in that hole.----The high speed fuel metering jet ( high speed orifice ) is way inside there and needs to be CLEAN.----Look for it , find it.

 

[hv]

Go it.

Is there any chance my fuel pump is not working properly as well? I did take the drain plug out of each bowl and when I squeezed the bulb fuel came out well. But maybe that's not a fair test.

 

[racerone]

Some testing and inspection on your part will find the problem.------I remember 52 years ago when a customer would roll a lawnmower into the shop.-----I would ask a few simple questions because I needed INFORMATION to help people.----I would reach for the gas cap on the tank.----Folks would say " sonny the tank is full "------I would still take the cap off to look.----I replied that I want to smell the gas and look for water in the tank.----Many old folks left the shop with a " thank you very much for your skills young man " and hand shake.

 

[hv]

So I finally got time to take the carbs off and clean them thoroughly, all jets and orifices. I also replaced the needles and seats while i was at it. Did a drop test before heading to the river and it seemed fine. slight change in sound when I pulled off each plug, but the engine never died, like before. I also checked to make sure the fuel pump was working which is was.
At the river it ran great - first time all summer, even got my teenage son up on skis - for about 2 minutes, then it throttled back and did the same thing I saw before - never got up to full revs again. Fuel lines are new 3/16th tubing. the only thing I have not replaced is the line with the bulb in it could that be whats causing the problem - hard to imagine.

not sure where to go from here..

 

[juno pierrat]

haven't read back thru all the posts but do you have a fuel filter?

 

[oldboat1]

You are apparently using an inline tester for spark -- need the open air adjustable style to measure spark (test ignition strength). Test each wire with all plugs removed.

 

[hv]

No I tested each spark with a gap tester set at 7/16". No I do not have a fuel filter. Should I have one inline? if so what kind? I have heard different opinion on this. will it affect the mixed fuel?

 

[racerone]

Test run with another tank and hose.----Borrow one from a buddy or someone at the launch ramp if you live in a friendly small town.----You are aware of possible water leaks on those 3 exhaust plates on the side of the block ?---That can leak water into the engine and cause performance issues.----Filters do not filter out oil !----Not sure where that tall tale might come from.----Once again that question proves that oil mixed with gas and 2 stroke engine operation is a mystery to some !

 

[juno pierrat]

spin-on water separating fuel filter,many brands , will not effect oil mixture