problems starting 25hp Johnson 1981

[jasper60103]

Just wondering if anyone had any tips for starting hot?
Seems to start-up OK when cold, usually within 2-3 pulls. It will sometimes die out though, but will start right back up. Btw, it runs like a champ and idles fairly well once it gets going.

I have more trouble getting her started hot. When I have problems I'm easily frustrated. I try starting with the choke in/out several times and adjusting the throttle until I finally get it going. Last time out, a good samaritan came along after noticing me wear my arm out. He made sure the vent was open and took a quick look under the hood. He concluded that maybe I flooded it out and suggested I take the choke off, and it did start after a few pulls. It died after about 30 seconds, but started up again.

Do you think my throttle position could be causing the problem? The start position is notched on the tiller handle, so I really don't know if this is really the sweet spot. Also, I never adjusted the idle speed. It was set by previous owner. Could it be the problem?
Should I choke when the engine is hot? How can I find the throttle start position?

At this point, I'm thinking my problems are operator error as I'm still fairly new to boating. Anyway, you have to start somewhere.

Thanks for your advice.

jasper

FYI. 1981 Johnson 25hp. Again this is my first season with this motor and boating.

 

[Blade_Link]

Re: problems starting 25hp Johnson 1981

you might need to ajsut your start position, give it a bit more gas and once it starts give it a bit more, your idle might be a bit low, but apart from that i cant think of a cause off hand

 

[tashasdaddy]

Re: problems starting 25hp Johnson 1981

those mark should have never been there imho.
to start that motor warm.. in neutral, turn throttle as far as it will go,(it has a neutral stop, that will only let it go so far) no choke, pull rope. you are flooding it bad if you use the choke on a warm motor, it is for cold starts.

you also may need a carb cleaning & rebuild kit, and linc n sinc. new fuel lines, ethanol.

http://forums.iboats.com/showthread.php?t=299680

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

Thanks, guys. I'll try full throttle for start and no choke (when warm). I think using choke maybe my problem.

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

...
you also may need a carb cleaning & rebuild kit, and linc n sinc. new fuel lines, ethanol.

http://forums.iboats.com/showthread.php?t=299680

I went out on the lake today. It's not my starting procedure. It was hard starting cold as well. It starts, runs for a few seconds, sputters and dies. It ran like a champ once I got it started, unfortunately, I was too scared to stop and fish. One thing I notice though, GPS speed was only about 12 mph full throttle. I would expect around 22+mph with this rig (see pic). I'm a hefty boy, but I didn't have a lot of gear. I estimate the load about 900 lbs total. The engine sounded great though. I ran it WOT for about 45-60 mins with no problem.

I guess I will start with the carb and linc n sinc. Unless anyone has easier things to try first. FYI. I put in a fresh set of plugs before going out today.

thanks,
jasper

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

More info.
TD got me curious about the fuel lines.
I took a closer look at my motor and see a tiny leak at fuel line connection to the carb. Do you think this could be the reason for my hard start problem?

I plan to repair it anyway. Just hoping this will cure the hard start.

 

[Silvertip]

Re: problems starting 25hp Johnson 1981

You are searching some magic cure but you really need to start with the basics. When was this engine tuned up last? Have you looked at the spark plugs recently. Are "both" of them actually firing. Believe it or not, many folks cannot tell if one or more cylinders are miss firing or not firing at all on a multicylinder engine. A spark check hot and cold is in order. A compression check is in order on a hot engine. Low compression makes a hot engine hard to start. Not having to use the choke to start the engine is a yes and no situation. It all depends on how long you had sat before trying to restart. Engines with manual chokes can't tell you whether it needs choke or not so some experimentatin is required. Chokes do not need to be full on or full off either. There are times (during warm up for example) when partial choke is useful. You might also give the primer bulb a squeeze or two before trying to start a warm engine. Since your starting issue seems to be getting worse, that would point some carburetor issues. When was a cleaning and rebuild done last? Water in fuel? Old fuel? Take a logical approach to this issue. Don't begin throwing parts it in hopes of getting lucky. Troubleshoot and then fix what's wrong. Use the money you save for other stuff.

 

[jasper60103]

Re: problems starting 25hp Johnson 1981 (updated w/video)

Re: problems starting 25hp Johnson 1981 (updated w/video)

Ok, I checked compression and getting 115 top and bottom hole. Also, I have blue spark jumping 3/8" gap on both wires.

I recorded the motor idling today. Pees like a race horse. Idles down slow. It took 10-15 pulls to get it going though.

Would the next step be to kit the carb?

http://www.youtube.com/watch?v=gfBQ0_lBkfU

jasper

 

[Daviet]

Re: problems starting 25hp Johnson 1981 (updated w/video)

Re: problems starting 25hp Johnson 1981 (updated w/video)

Recheck your spark at 7/16 and see if it is blue and really snaps. You have a low speed fuel adjustment on your carb, with engine running try opening the needle valve 1/4 to 1/2 turn. If that does not make any difference it may be time to overhaul the carb.

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

Daviet,
I'll recheck the spark with 7/16" gap.

Regarding the slow speed setting. By open, do you mean more rich?
I played with the slow speed a little today, but I put it back to original setting thinking it could make matters worse. I think it did sound better more rich.

Oh, I forgot to mention I noticed fuel leak from the bottom plug (right). Could this be from idling too long?

thanks.

 

[Elbo]

Re: problems starting 25hp Johnson 1981

It's impossible to set a spark plug gap at 7/16".They set @.30 .Forget the markings on the handle and do what it takes to make it run.I have that engine ,and it will wear you out if it's not right.Try this.At the bottom of the carb bowl there is a bolt.That would be the bowl drain and access to the high speed jet.Get some spray carb cleaner and take out the bolt.With the straw that should come with it be sure it's up against the orfice and blow it out. That should clear your high speed jet.The screw at the top is your slow speed idle adjustment.Clear the high speed jet then work on idle.Hint,on your low speed idle, screw it all the way in,not hard till it stops.Back it out 1 1/2 turns,Then easy in 1/8 turns screw it (IN ) until desired results.

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

"It's impossible to set a spark plug gap at 7/16".They set @.30"

I was referring to the spark tester gap. Thanks for the tip on the highspeed jet.

 

[jasper60103]

Re: problems starting 25hp Johnson 1981

Daviet,
I checked my spark again.
Nice snappy spark jumping 7/16" gap. So I think we can rule out the ignition system.

I put it back the barrel again and opened the low-speed needle 1/4 turn like you suggested.
3 pulls it started right up! That's even after I realized I forgot to squeeze the fuel bulb.
I let idle for a long while and let it reach operating temperature. Then I shut it down and restarted it a few times, no problem. Also, I let it sit for 40 mins until cold and it restarted again within a few pulls. I repeated cold start a couple times and no problems. I learned my engine prefers partial choke at times.

Considering this, my hard start problem appears to be carb related. I need to get a tach to fine tune it further.

Thanks again for your help.