1999 Johnson 25HP - Power/Planing issue

[Pecenje]

I have a 99 Johnson 25hp 2cylinder...
Model# J25ELEED

I'm only getting 10mph out of it on a 16.5' aluminum side console fishing boat
i'm getting 5mph out of a 4hp 1 cylinder kicker motor
transom is a longshaft and so are the motors

any ideas?

I've played with the tilt pin settings and nothing major (1mph)
I've just hooked up a tach and will report back on the Max RPM at WOT and some RPM vs MPH ratios
I've added a hydrofoil and it still won't plane
The prop has the following markings, i can't cross reference them to anything??

79657 this is clearly stamped, nothing is missing
OP6371

i figure the boat should be running 18-20mph at WOT

Any help would be appreciated

 

[jbjennings]

Re: 1999 Johnson 25HP - Power/Planing issue

My suggestion is to get a cheap air gap spark tester from an auto parts store (less than 10$). I suspect weak or no spark from one cylinder. Hopefully, it's due to a bad coil. Your spark should jump at LEAST 1/4" air gap with nice blue spark.
Good luck,
JBJ

 

[cfauvel]

Re: 1999 Johnson 25HP - Power/Planing issue

And the compression test ofcourse.

 

[5150abf]

Re: 1999 Johnson 25HP - Power/Planing issue

Correct, compression and spark check first then clean your carbs, 90% of these problems are caused by atiny peice of junk in a jet and it is very hard to detect a miss on a 2 cylinder 2 stroke.

Get it running and pull the plug wires one at a time, if it doesn't change or die I would suspect a carb but do comp and spark first so you know they are good.

You can also, and use due caution, squirt a little gas in eac carb when it is running, if it dies or bogs that is good, if it runs better it almost certianly a carb issue.

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

Did a compression check and 120 and 117

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

I've been reading up, and it looks like i'll be doing a carb rebuild on it...

anyone have a step by step or how to for this?

 

[5150abf]

Re: 1999 Johnson 25HP - Power/Planing issue

Not really hard, take a pic of the linkage before you touch it so you have a good refrence when you put it back together and try not to move anything, if you take it straight off and straight back on you should be fine.

Never done your engine but generally there are 3 jets, no adjustments on a 99, the idle is at the top front of the carb the mid is at the top back of the carb and the high speed is in the float bowl behind the drain screw.

Do one carb at a time and keep the jets with the cover screw so you don't get them mixxed up and put down some newspaper so you have a super clean work area.

Remove all the jets and run a stranded copper wire through them, just pull back strands till the wire just fits, scrub it in and out a couple times and you are good, using some Sea Foam is recommended and blow air through all the passages, again some Sea-Foam and the wire are useful here.

If you don't have a compressor the air in a can for computers works really well and you will probably have to make a screw driver for the high speed, you need a long really skinny one to reach the jet but make sure it is big enough or you will break the ears off the jet, make it so it just fits.

It really isn't hard, just take your time and you will do fine, and lastly get an inline filter on it, haven't had a single carb problem since I got one on mine.

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

It's a single carb motor

Where did you put the inline filter? Under the motor cover or after the primer bulb?

 

[hidef]

Re: 1999 Johnson 25HP - Power/Planing issue

Install the fuel filter after the primer bulb in your fuel hose. There isn't a lot of room under the hood of your 25 for a fuel filter. There were two different 25s in 99 a two cylinder and a three cylinder. The twos are very rugged and reliable engine. Check your spark with a spark tester if you haven't done it first. It needs to jump a 7/16 gap on both plugs this will verify that your coils are good. Clean your carb you will have to remove the starter to get to the nut on the port side to pull the starter. Also check the filter screen on the fuel pump to make sure that is clean.

The carb is simple to clean and rebuild. Get the OMC rebuild kit you will want to remove all of the welch plug covers and clean underneath them as well as replace the float and needle valve. If you don't have a service manual get the OMC/BRP Service manual do not buy a seloc or clymers they aren't very good. The OMC will have a step by step instructions. You can a new one at http://www.marineengine.com/parts/parts.php#manuals or find one cheaper on ebay.

Good luck

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

i have the 2 cylinder model... glad to hear it is rugged and reliable...

are the welch plug covers the steel cap looking things?

how do i remove them? how do i re-install them?

i plan on getting the Sierra Kit 18-7222
is there any difference between it and the OMC 0396701 my local OMC dealer is less then reliable for delivery dates...

here is what's included with the Sierra Kit, looks identical to the OMC kit

 

[jsimmons1970]

Re: 1999 Johnson 25HP - Power/Planing issue

Stick with the OMC parts. You can always order online from http://shop2.evinrude.com/Index.aspx?s1=2jcepsgaks8abmtlkrc25ic2r5&catalog_id=0&siteid=1.

 

[Cofe]

Re: 1999 Johnson 25HP - Power/Planing issue

You tube has video on removing and replacing welch plugs.

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

The carb is simple to clean and rebuild. Get the OMC rebuild kit you will want to remove all of the welch plug covers and clean underneath them as well as replace the float and needle valve. If you don't have a service manual get the OMC/BRP Service manual do not buy a seloc or clymers they aren't very good. The OMC will have a step by step instructions. You can a new one at http://www.marineengine.com/parts/parts.php#manuals or find one cheaper on ebay.

Good luck

how critical is it to change the welch plugs? and clean underneath them?

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

You tube has video on removing and replacing welch plugs.

All i see is videos for the big ones (frost plugs) for cars...

none small carburetor type...

 

[watergecko]

Re: 1999 Johnson 25HP - Power/Planing issue

Make certain u remove/clean under those welch plugs!!! Do not take a shortcut here, or you will be redoing it in a week. I just carefully drive a screw into the center and tilt out with a pliers. Just be careful not to drive too deep or scratch the channels. Those are your idle circuits. Once you see under one, you'll always know what youre dealing with. Im sure theres a vid on youtube.

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

how about the lead shot on top? does that have to come out as well?

If so, how?

 

[Oldyellow71]

Re: 1999 Johnson 25HP - Power/Planing issue

Yes, you want to take all the welch plugs out, even if there arent jets under each one, there are usually little holes in there that need (or could need attention). Trust me, when you have it off just do it. I have tried to do it fast on a 65hp once and didn't pull all of them. Needless to say I did it again two days later and had to "locate" the plugs I threw away in the garage trash can. There are many ways to remove them as the guys above posted. I just take a sharp awl, tap it once with a hammer and pop it off. Oh, and also as mentioned above the copper wire is important as it is soft!! My buddy at work had to buy another kit after he scored a jet by using safety wire instead.

 

[jbjennings]

Re: 1999 Johnson 25HP - Power/Planing issue

how about the lead shot on top? does that have to come out as well?

If so, how?

I would NOT remove the lead shot. BTW, did you ever check to see if spark would jump a 1/4" gap on both cylinders?
Curious,
JBJ

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

i tried to do the spark jump but the tester broke...

what a cheap POS!!

gonna return and try it again...

tach worked and i'm getting 4500rpm at WOT and it's 11mph top speed

 

[Pecenje]

Re: 1999 Johnson 25HP - Power/Planing issue

also noticed that in this image...

#4 is supposed to be a core plug... mine has a a wire mesh inside and no plug??

http://shop2.evinrude.com/Index.aspx?s1=n1dug4bmmjn39t5ivpuvb8uof4&catalog_id=5&siteid=1