'97 Evinrude 25hp throttle issue

[WhiteRice]

So I have tried several things with this motor and can't seem to get it to open up beyond a fast idle speed. Motor starts on just about every first pull (rope start) and idles fine. I have cleaned the fuel lines, tank, disassembled all three carbs (and cleaned), checked compression (125, 124 and 119) and replaced the plugs (they were slightly fouled). Motor was having rough idle issues and sporadic starting problems but those seem to be resolved after doing the above. I have taken the boat out twice and it drives great going through the marina and through the canals in the neighborhood we launch from. As soon as I clear the area and try to open it up it just wont go any faster than about 7-10mph (as indicated on my GPS). It does not go up and then "bog out" but rather just limited power. Almost like it's limiting itself. I visually inspected the throttle cable while in motion and it appears to be moving all three carbs to WOT and advancing the timing to 20 (what the sticker on the motor shows for timing), but just no cruising power. What am I missing? This is my first outboard but the concept and minor repairs of small motors is not new to me.

 

[jbuote]

Hmmm....
Maybe try connecting a timing light when you're out running, and see if you're losing spark when at throttle?
​I guess it's possible it's losing spark at RPM, but have normal spark towards idle..

Still not an expert here.. lol...
​Just a thought..

 

[flyingscott]

Compression and spark test need to be done.

 

[WhiteRice]

Compression numbers were 125, 124 and 119. I checked the spark with one of the plug testers and it was set at 3/8" Spark was nice and blue. Interesting point about checking the timing while out

 

[jbuote]

Well, the thought was not so much checking the timing, but rather using the timing light as an indicator to see if you're losing spark.. IF you don't see steady flashes at RPM, then it's missing. IF it flashes steady, then it's ok...
​If that made any sense... LOL

 

[ondarvr]

Pull of a plug wire and see if it runs worse with each try, if it doesn't you found the problem cylinder, and do it while trying to go fast.

 

[WhiteRice]

This may be a little bit of a goofy question, but is there a better way to check this without pulling plug wires while on the water? Where I take it is an hours drive one way

 

[ondarvr]

They can run OK on two cylinders when out of the water and there's no load, unless you try it in the same way that's having problems it may not be noticeable. You can always try on the hose before you go out on the water to see if you find something though.

 

[WhiteRice]

True. I do have a 50 gal flush barrel I use over the muffs if that's what you are referring to when you say "the hose".

But let me ask this... Should my throttle control open up the RPMs through its entire distance? When throttling up from "no wake" speed, it works it's way up to it's 7-10 mph speed about 1/3 from full throttle position. The remainder of the distance toward full throttle makes no adjustment in RPMs at all.

 

[jbuote]

Yeah.. it should.. Even without the engine running.. If you advance the throttle, does the timer base advance to full and then the throttle butterflies continue to open through the whole range of the throttle control, or does timing AND throttle butterflies stop moving before you get to full throttle on the control?

 

[ondarvr]

The tests are to rule things out. Right now you have no idea what the issue is, after this test you'll either find a problem, or know you have spark and its running the same on each cylinder. With this knowledge you can make the next step in the direction it leads you.

 

[WhiteRice]

The timing base advances from 10 (idle) to 20 as soon as I go out of neutral. 20 is as far as the timing will advance (it appears to max at 30 based on the markings) and it appears that the butterfly actuator continues to operate all the carbs through the entire motion of the throttle.

 

[racerone]

Checked reed valves ?----Checked flywheel key ?

 

[WhiteRice]

Would there be any harm in attempting to throttle up the motor in a flush barrel with the prop off vs. trouble-shooting on the water?

 

[jbuote]

I've asked the same question, and the answer was....
​Do NOT throttle up past say 1500-2000rpm MAX on muffs or test barrel...
​(Edit: And I would NOT take the prop off either.. NEED the prop, or test prop for some load).

​Reason is, you don't have the same load on the engine as you would in the lake..
​Even a test barrel wouldn't have the same load on the engine as the lake would..

​Without the proper loading, you risk a runaway situation..

​High RPM, or WOT tests should always be done on the lake, while in motion..

​At least that's what I've been told by the pro's here, and I tend to believe them.. lol

 

[WhiteRice]

Well, that sounds....... sound. Thanks

 

[WhiteRice]

Ok... so I didn't get it on the water but I started it up on the barrel and pulled one plug wire at a time. No change in idle speed or running with each plug. Tried them in different order but no change with any of them...

Made the mistake of pulling two off and got a nice "hand-shake" from the power pack :-/.

Will pulling the plug wires to check how the motor runs only work while it's I gear on the water? I would think not but I am uncertain.

 

[WhiteRice]

No Title

Reed valves also appeared to be in good shape. They all opened easily with very slightly pressure. Although I did find a small vacuum line that came from the intake manifold that was disconnected from the powerhead. It was not the blow-back line but it "T'd" off from another vacuum line going into the intake manifold (circled in yellow on the pic) I took the carbs off again to confirm nothing is clogged after running about a half gallon through it today. Any idea what that vacuum line may do? Could that possibly be keeping the reed valves from operating properly?

 

[jakedaawg]

Those are puddle recirculation lines I bet. I do not ever see any 3cyl 25's though so don't hold me to it.

Has this motor ever run good on this boat? If no then is it possible you have too much prop or too little motor for the vessel?

 

[WhiteRice]

This is a 25HP on a Carolina Skiff J16. Very small, very light boat. It should plane out with 2 ppl plus gear at about 20mph+. I have only had the boat for about 4 weeks and have had it out twice. As stated previously the top 2/3 of the throttle does nothing. It does not even increase the RPMs so even if the motor was overworked I would still get increased RPMs but limited acceleration .