1989 20 HP Johnson power upgraded to 25 HP for zero dollars

[Siguz]

Siguz » 28 Jun 2014, 10:17[/url]"]

Are fuel pumps a common problem with these motors?
I think mine is starting to fail.....

If I have this right you basically put a 25hp intake on a 20 hp motor and you are starving for fuel.?.
The 25 may have the same carb or carbs but your main jets are sized for 20 Me thinks....You may be starving for fuel because the main jets are too small causing a lean condition. Swapping jets and putting a fuel pump rebuild kit are simple. The book may even list a different part number for the jets. You let in a lot more air and no more fuel unless I missed that in this long thread. Did you squeeze the bulb when it acted up?

Sorry
I should have clarified.
The motor w as running fine after the mod for about 3 weeks then all of a sudden couldn't hold idle.
Rebuilt the carb.... Ran well again.
One week later.... No power can't plane.
Found that if I pulled the choke half out it would run better.
All of a sudden runs great again.
In certain there is av few issue.


As for mod.
Carb and jets are the same.
The manifold is also the same but the restriction had been removed.

 

[Stumpalump]

Ethanol fuel that we get today is prone to getting brown jelly like goo in it. Best thing to do as a first step is to give it a fast idle and block one carb at a time with a rag. This creates a high vacuum that will often draw the jelly thru the carb and you won't have to rebuild it. A fresh fuel line is always a good plan if your fighting a problem. I just buy good automotive fuel line and rebuild the bulb by taking apart the check valves in the end and cleaning it all up. Those primer balls will work one minute and not the next. Pull the ends off the bulb and clean it up but don't get the ends swapped. Fuel pump....Is so easy and cheap to rebuild that you might as well knock it out. I don't mess with fuel problems long. I cut my losses and go thru the whole thing once and then I'm done for years. Start with the crap in the bottom of the tank and clean and replace everything you can.

 

[Johny25]

Im guessing the mod has nothing to do with why it is acting up...or it would have happened right away. Could be something as simple as an air leak in the fuel tank line. But it does sound fuel/carb related. Small air leaks can cause havoc

 

[Siguz]

Looks like I got it sorted out.
Rebuilt carb and fuel pump.
Running beautifully again.

I have noticed that the primer needs to 2 pulls to create any vacuum at all. I'll t replace it once the budget allows for it.
Thanks guys

 

[Johny25]

Siguz » Today, 06:40[/url]"]Looks like I got it sorted out.
Rebuilt carb and fuel pump.
Running beautifully again.

I have noticed that the primer needs to 2 pulls to create any vacuum at all. I'll t replace it once the budget allows for it.
Thanks guys

Primer is probably fine........I had to pump mine 3-4 times always first time starting motor

 

[Siguz]

Good to know.
I will double check all the lines though.

 

[Siguz]

Here's a question.....

I was looking through the online parts catalog and noticed that you can buy carb jets suitable for 30-35 HP motors.
Would it make any difference to install these larger jets without replacing the carb itself?

 

[Siguz]

Siguz » 23 Jul 2014, 05:40[/url]"]Here's a question.....

I was looking through the online parts catalog and noticed that you can buy carb jets suitable for 30-35 HP motors.
Would it make any difference to install these larger jets without replacing the carb itself?

Note: Jets from 20-25 are the same

 

[Johny25]

if you add more fuel you have to add more air......hence the larger venturi on the 30-35 carb

 

[Siguz]

if you add more fuel you have to add more air......hence the larger venturi on the 30-35 carb

Agreed.
I have already punched a few holes in the front of the hood to create somewhat of a 'ram air' setup. I just wonder if it'll be enough air.

I might just spend the 40$ and give it a try.

 

[Siguz]

Installed larger carb today.
Had to cut manifold a little further to accommodate.
I guess I didn't cut it out fully last year.
Hopefully I'll be able to get on the water before the end of the month.
Water levels are rising and ice is melting.... Not fast enough though.

 

[EZ707]

Thats fun. I had a 35 hp carb on that same motor and i love it

 

[Siguz]

got the Carb on.
41km/h with a 10x12 prop.
Gonna try a 10x13 and see what happens
Motor seems to run better now that there are no restrictions.

 

[EZ707]

Very nice! Im thinking of doing the 10x13 prop myself. Let me inow how it works out

 

[Siguz]

43 with the 10x13.
I think it can probably handle 10x14 but that depends on each application.

 

[Randolphdmobius]

I found a 25hp carb and intake for my 1982 20hp and do a similar mod.
My engine has a reducer elbow on the fuel line from pump to carb, (I assume all the 20hp engines from this era do), would anyone know if it’s wise to replace this with a larger fuel hose and do away with the reducer?

 

[RaisedByWolves]

Dont know why the quote function changed....

My engine has a reducer elbow

A pic or some size reference would go a long way here, but I dont think there would be much of an issue using what's there as restricting fuel for whatever purpose from the factory would be odd.

Ie, The high speed jet is relatively tiny in comparison to most fuel line.