70 HP Evinrude bogging down

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Cadet
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Oct 30, 2009
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I have a 84 Evinrude 70 HP motor that bogs down. A was on the river last week and was on plane and it slowly started losing speed and bogged down with the throttle all the way open. I limped back to the boat dock and the next day it ran good for maybe a minute then did the same thing. I took it to a guy and he said that 2nd and 3rd cylinder were water wet and replaced the head gasket but its still doing the same thing.

Anybody feel like helping a guy trying to have a dependable fishing boat? Any ideas?
 

oldcatamount

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Re: 70 HP Evinrude bogging down

Sounds like it may be a fuel issue. Make sure your tank/s are venting right. Look at the fuel lines, filters, clamps, etc. Older fuel lines will fall apart on the inside and plug the flow of fuel.
 

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Re: 70 HP Evinrude bogging down

Looked at the fuel lines and everything looked Ok to me, It has a 6 gallon tank and it was vented and i primed the ball and gas was flowing good.
 

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Re: 70 HP Evinrude bogging down

Plus compression is around 120 on all 3 cylinders and they all are firing.
 

eavega

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Re: 70 HP Evinrude bogging down

Run the motor until it starts to bog down, then check spark and compression. Sometimes you get electrical components that start to short when they get warm and expand. Won't manifest itself when engine is cold.

Just a thought.

-Rgds
 

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Cadet
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Re: 70 HP Evinrude bogging down

Run the motor until it starts to bog down, then check spark and compression. Sometimes you get electrical components that start to short when they get warm and expand. Won't manifest itself when engine is cold.

Just a thought.

-Rgds

Will try this, any other thoughts?
 

boobie

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Re: 70 HP Evinrude bogging down

Try hitting your choke/primer when it does it and see what happens.
 

boatmore

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Re: 70 HP Evinrude bogging down

When the motor starts to bog down have someone else pump the primer bulb while you are still WOT and see if the engine takes off again. If it does, more than likely it is the fuel pump. Also if your engine is using a quick connect on the fuel line leading to the motor, make sure you check that the orings/seals are not leaking and allowing air into lines.
 

imokintex

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Oct 14, 2010
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Re: 70 HP Evinrude bogging down

I had the same problem on the same motor a few years ago and it was a bad coil.
 

mrcj001

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Jul 25, 2008
Messages
313
Re: 70 HP Evinrude bogging down

Could it be a bad exhaust gasket?

Probably not........

The ignition system on that motor is over 25 years old. When the engine gets hot some componets start to fail. Try troubleshooting the ignition system when it acts up.
 

jtexas

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8,646
Re: 70 HP Evinrude bogging down

*fuel line holding pressure? is the bulb still firm after it starts acting up?
*how old is the gas?
*what spark plugs you running, what condition are they in? what do they look like after the motor's been running? I assume you checked 'em for water after the repair?

What I'd do:
*inspect the tank for water, debris.
*inspect the fuel filter(s).
*airbox cover off, pressurize the line with the primer bulb and tilt the motor full up -- does gas run out the carb throats?
*Spark test (not a "spark plug" test): get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it won't fire in the hole under heat & compression.
 

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Re: 70 HP Evinrude bogging down

*fuel line holding pressure? is the bulb still firm after it starts acting up?
*how old is the gas?
*what spark plugs you running, what condition are they in? what do they look like after the motor's been running? I assume you checked 'em for water after the repair?

What I'd do:
*inspect the tank for water, debris.
*inspect the fuel filter(s).
*airbox cover off, pressurize the line with the primer bulb and tilt the motor full up -- does gas run out the carb throats?
*Spark test (not a "spark plug" test): get an inline spark tester (couple bucks at autozone), set the gap for 7/16", clip it to the engine block, attach the plug leads (one at a time) and look for a strong blue spark while cranking. If it can't jump a half-inch gap in the open air without a spark plug, it won't fire in the hole under heat & compression.

Thanks, I will do all of this when I go get my boat back.

I just spoke to the "shop" that has my boat and he said something about a bearing with groves that keeps gas in the third cylinder being bad and that its none replacable. He said that he hasent checked it yet but thats what he thinks. Does this make since at all?
 

jtexas

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8,646
Re: 70 HP Evinrude bogging down

Lower crank seal maybe?
Still getting water in #3?
 
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