25 hp evinrude, need help

[captbuddy]

I am trying to help a friend out. His 25 hp will not let you run it pass, lets say about half way. I have taken the carb off and soaked it in carb cleaner. I took two jets out and soaked them while out. He has new tank and hose. I can run it up while on land and even in gear while on the trailer but when you put a load on it, in the water it will shut down if you try to run wot. Any hints will be appreciated. I told him I thought it might be the coil? Thanks in advance.
captbuddy

 

[stormchaser]

Does it run OK when cold or first started? One of the fist signs of over heating for older 2-stroke Johnson & E'rude engines is bogging down and VERY poor performance once ran for a little while. I ran in to this problem with my 1975 Johnson 50. It ran fantastic for the first 20 minutes. And the mechanic could never reproduce the problem, because he would to the test runs with the cowling off which kept temps down. Consider a water pump job and replace the little thermostat that's under the cowling if it hasn't been done in a while.

 

[captbuddy]

No dave, it has a new water pump on it. It pisses real good and runs the same with the cowling on or off. It sounds a little rough when running but it will run on low speed. Just boggs out when you try and run wot.

Thanks,
captbuddy

 

[gbharrington]

Fuel pump?
Try squeezing the priming bulb when you attempt WOT. That was my problem.

 

[captbuddy]

Greg, I tried that also. No change while running. Like I said, you can run it wot while on he trailer with the water ears on and even put in gear and run it wot and it runs good. Just not in the water under the load.
captbuddy

 

[gbharrington]

Coil and/or condensor would be my next choice.

 

[stormchaser]

First, what year is the Engine? I don't suppose you have the model number from the mounting plate? Might help is we knew more about what level of complexity this engine has.

Still sounds like fuel (or air) starvation to me. Have you checked the fuel filter screen? The older Johnson/E'Rude engines don't have real filters, just a screen on the fuel pump. The fuel pump is a diaphragm type attached to the motor (starboard side if facing the aft of the boat on the 50). Also, if an older engine, have all the fuel lines been replaced with ones compatible with ethanol? What about the rubber/plastic bits of the carbs?

 

[krush]

First, did the motor ever run correctly for him? When did the problem start? (these are important questions)

Next, for sake of diagnostics I'm going to assume that the carb job is done correctly. If you pulled the jets out and soaked the carbs over night and BLEW all the little holes out with compressed air, hopefully you got it all clean. The compressed air part is important because on these smaller engines the little passages in the carbs are quite small.

The reason I asked if it ever ran correctly is because I had a huge headache on a motor I got for free once. It would idle fine and be ok up to 50%, but over that it would bog out. It was running too rich. It had 3 carbs and it turned out that somebody switched the main jets with the bowl vents on 2 of the carbs. The bowl vents look like the jets, but are bigger orifices.


And lastly, if all is well on the carbs, these outboard engines usually have two sets of ignition components. One for high speed and one for low speed. I'd have to dig and look up info on a 25hp johnrude, but the bigger mercury flavors have a high speed section of the stator and a low speed section of the stator that is used to make the electricity to send to the coils for different RPM.

Also, the timing advance is controlled on most outboards by rotating the pickup underneath the flywheel. This normally doesn't change with time...so if the motor used to run correctly and nobody messed with it, it is likely fine.

 

[stormchaser]

If it helps, here's an online parts catalog for Johnsons (same site covers many brands). I find the diagrams quite helpful. Also, haveing a shop/service manual for the outboard helps.

http://www.boats.net/parts/search/BRP/JOHNSON/parts.html

 

[Andy B]

Try running it with the choke pulled if it runs good then ,pull and clean out the main jet in the carb,depending on the year the mixture knob screw has a seal on it if the seal is bad it will run poorly.and if it's really Old check the points
Andy

 

[Sailor John]

2 things that have caused me 'outboard grief' in the past:
Old fuel, and vent caps that don't vent. (just loosen the cap)
Sailor John

 

[captbuddy]

I changed out the two coils and it still does the same. I think it ran a little better but it still would not run WOT in the water. I did not change the condenser. I have left my friend now in Mahatten, KS and am heading south towards Mississippi. I did not soak the carb overnight and I did not have air to blow it out. I told my friend to take it to a mechanic before spending anymore money on it. Thanks for the help.
captbuddy

 

[stormchaser]

1. You have good spark
2. No air restrictions
3. I assume compression is at least 110#, new/rebuilt spec is 140# (my 1975 Johnson 50 runs like great with 122# on one cylinder and 120# on the other)
4. NOT overheating
5. Fuel is still questionable


So, you have 3 out of 4 things needed for suck-bang-blow. The only one left to consider is fuel. I'd still bet it's a fuel problem of some sort. My thoughts? Pull carbs and do an overnight soak of the carbs and throw a repair/rebuild kit on them. The kits are under $30 each. Then REPLACE the fuel filter screen and the 3 fuels lines inside the engine. There is one that goes from connector to fuel pump, one from fuel pump to carb1, and finally one from carb1 to carb2. If they were originals or replaced before 2008, they are (or could be) susceptible to damage/deterioration from ethanol. If there is no inline fuel filter on the hose from tank to engine, consider splicing one in. A disposable clear filter should be under $5 and good stainless clamps would add another couple bucks...but it could save a ton later.

 

[rmatt]

Sounds like a lean(starving for fuel) fuel condition to me.