20 hp Evinrude

[craigrs8271]

I need Help!!!!!!!
I bought an older boat for crabbing in the bay. I figured it was only $450 for the boat with a fish finder & 20 hp Evinrude that ran.
It has a 1988 20 hp Evinrude on it.
When I bought it the motor ran rough..It was sitting for a year,"""SO THEY SAID!!!"""'' I figured the basics it will run good......

I took it home put new plugs, I found the tube in the carb. to be broken. I ended up buying a used carb & boiled it out putting a new carb kit into it.
I fired it up & it still ran rough.
I cleaned out the fuel filter, took apart fuel pump cleaned it up. I have a new gas tank ,new hoses & fittings.
I have done a compression check with results being 125lbs in both cylinders.
Both coils are sparking good !!!
It fires up & idles a little ratty & when I put the throttle to it thats the end of it, dies out ..
Any IDEAS????
thank you
craig

 

[HighTrim]

Re: 20 hp Evinrude

Your compression is great, you say its sparking well, so you must look to fuel delivery.

Will pumping the primer bulb pick it up? Spraying pre mixed fuel into the carb? Choking it out? Was the carb fully rebuilt, all orifices completely cleaned, floats adjusted? I assume the vent is open on the gas tank?

Get a vacuum gauge and hook it inline on the fuel hose before the engine, along with a clear section of hose. Take it for a spin, noting the readings and monitor the fuel flow through the clear hose.

Findings:

-Vacuum of less than 2 inches and air bubbles in the clear hose indicates an airleak into the fuel system
-No air bubbles and less than 2 inches indicates a bad fuel pump
-Vacuum over 4 inches indicates a restriction.

Sample gauge

"http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&sspagename=STRK%3AMEBTOX%3AIT&viewitem=&item=4610113711&_trksid=p3984.cTODAY.m238.lVI"

Also if it is dying when throttle is applied, check all applicable carb settings as per your manual. Check to see if the timer base (starboard side, under the edge of the flywheel, linked to the throttle lever) moves smoothly without sticking when you advance the throttle.

Take the airbox cover off & observe whether the throttle plates are parallel.

Also, the timer base should start it's travel before the throttle plates start to open, or else your girl will fall flat when you try to accelerate.

 

[jbjennings]

Re: 20 hp Evinrude

Sounds like you may have a vacuum leak to me. Or your float may be improperly adjusted. How do you know you have good spark? Had to ask--that spark gives me some grief every once in a while.
JBJ

 

[JB]

Re: 20 hp Evinrude

Check for faulty gaskets on the carb, reed assy and bypass cover too, Craig. They often dry out when sitting a long time

 

[samo_ott]

Re: 20 hp Evinrude

Also, does it run any differently with the hood on or off?

 

[craigrs8271]

Re: 20 hp Evinrude

Also, does it run any differently with the hood on or off?

NO change if hood is off or on

 

[craigrs8271]

Re: 20 hp Evinrude

Check for faulty gaskets on the carb, reed assy and bypass cover too, Craig. They often dry out when sitting a long time

I have heard of this & was thinking about making it my next move. Any easy way of checking ???

 

[JB]

Re: 20 hp Evinrude

Spray some dish soap on the outside of them. If they are leaky you will get bubbles.

 

[craigrs8271]

Re: 20 hp Evinrude

I have not done alot to the motor since I have last posted.
I did however discover when I pulled the new plugs ,they were SOAKED with fuel.
Why would that be ?????
Again it is getting excellent spark it runs until I throttle up on it then it dies out.
Craig

 

[F_R]

Re: 20 hp Evinrude

So, you put a used carb on it. Is it the correct carb for the motor? I suspect you have a problem with the high speed jet orfice plug. Missing, dirty, wrong one, whatever. Or, if you are trying to use a carb from a bigger motor in an effort to increase horsepower, you may have a problem there. It doesn't always work that way.

 

[BruceAML]

Re: 20 hp Evinrude

What is the part number of the original carburetor and was is the part number of the carburetor that is now on the motor?

 

[craigrs8271]

Re: 20 hp Evinrude

You said something that caught my attention........
Instead of buying a new tube or carb. on the weekend with the Marina being closed, I went to a guy that works on outboards around here.
He said he has another carb it was off of a 30 or 35 hp Evinrude. It would work he says. He showed me the carb which they looked to be the same. He also told me the only difference was the intake hole was bigger on the 30,35hp motor. He showed me my intake verses the intake on the 30,35hp. He also says it would add more HP to my motor.
I not only bought his story ,I bought the carb.
So I waited while he boiled the used carb & had him put in the 2nd carb. kit I had purchased for the orig. carb.

Is this right ???

Thank You MUCH
Craig

 

[kynolan2183]

Re: 20 hp Evinrude

Experience from my 1984 20hp to 30 hp upgrade

The 20 hp and the 25 hp used the same carb with different sized restrictor plates.

The 30 hp used a 30 hp carb and a 30 hp restrictor plate.

The 35 hp used a 35 hp carb and a 35 hp restrictor plate.

Look in the throat of your carbs and if you have a 30 hp carb the hole around the butterfly will be larger than the original.

When I upgraded my 1984 20hp to a 30 hp I found that when I cleaned and rebuilt the 30 hp carb I lost a gasket inside the bowl. This would cause the motor to just suck down tons of fuel a die at WOT.

The bowl is made with kind of a pipe in it that goes over the brass fitting (high speed ) from the carb. There is a gasket that must be there, it slides over that brass pipe and seals the bowl from the vacuume created by the engine.

Also make sure you now prop it correctly.
With mine I had a 13 pitch prop spinning 5700 rpm on a 14 36 jon boat (20 hp)

At 30 hp the same prop turned 6200 I had to get a 15 pitch prop.

By the way the boat was kind of dangerous at this point. but a *ell of a ride.

Kyle

 

[bgbass.1]

Re: 20 hp Evinrude

If that carb. is from a 30 0r 35 you need to change the intake to the same It will run a lot better.