25HP Update

[mtkinzel]

To ChampionMan, thank you for helping me get closer to IDing my motor that has no model number plate remaining. It is believed to be a 1991 25/30HP Johnson short shaft tiller model. The issue I noticed was that while running WOT is cut back to 50-70% and I no longer had top end. After swapping out new ignition coils and test ran it again with no improvement. I completed a spark test (blue spark present 7/16 jump) and compression test (110 and 105 or 105 and 100.....age factoring in here). The research I found indicated to me I needed to look at the carbs. Well, with the motor not running, in gear, I noticed the butterfly in the carb throat only opening 1/4 of the way with the handle in WOT position. HMMMMMM!!!!!!! Upon further investigation I found a broken starter interlock cable bracket (325326). As I move the handle to WOT the nuetral start plunger (325332) does not allow the throttle cam to continue its natural progression thus keeping the carb butterfly nearly closed. So in short, I am looking to replace the cable bracket and once correctly aligned will see if the cam is back in action. Thanks again. Mark

[ChampioNman]

Keep us posted.

[mtkinzel]

Well I was able to run it today and the linkage is good but the issue still remained. Disassembled carb, cleaned, installed new kit items. Prior to reinstall looked inside and saw what appears to be missing reed leaf. Good news is I guess I am learning more......sure hope there is light at end of tunnel. Will keep you posted.

[ChampioNman]

Sounds like you are making progress. Hurry up duck season is coming soon!!

[mtkinzel]

Replaced the reeds and it <u>idles fine</u>. Still not getting WOT performance (60-75%). Took cowling off and ran it.....it was back to normal WOT 100% screaming (for a 25.) Put cowling back on and back to UH-OH. I played with the primer while it was coughing and missing, no improvement. I tried squeezing the bulb, no improvement. It seems to cough and miss in mid-range like it isn't getting fuel. The bulb stays hard until the cough and it gets soft then seems to get hard again (fuel pump?). I changed out the fuel lines from the primer to the carb (two sizes 5/32 hose and the .0575 one if I remember right.)

So to date I have done the following:
Spark test....jumps 7/16 blue
Compression .....110-105 or 105-100
Replaced ignition coils
New fuel tank and hose
New fuel lines (primer to carb/intake)
Checked linc/sync....in line and good (did not do timing check...not sure how)
Carb cleaning twice and kits installed (double checked float).....may still be clogged high speed orifice?
Sea Foam decarb
New plugs QL77JC4
I also had to put on a new recoil spring and pull cord......come to think of it, all my troubles began soon after the cord breaking. Please tell me there is something easy I am missing here.


What am I missing .....except for the add this motor to the FOR SALE page? Seriously I had hoped to not let this beat me but it is looking more like I am over my head and need to take it in and take one for the team.

[ChampioNman]

Crazy question but is the tank a portable and the vent open?

[mtkinzel]

yes and yes.

[Chunder]

Do those things have a fuel pump, if so the check valve might be sticking. or the diaphragm has a hole in it.
Chunder

[mtkinzel]

I just pulled the fuel pump cover and cleaned the screen (it did not appear dirty). I removed the tank pick up tube and checked to ensure there was no blockage. I checked and reset the vent cap so that it was vented.

I ran it on ear muffs and it still idles well (low rpms) but the moment you give it a bit of throttle it coughs, sneezes, misses BUT does <u>not</u> cut off. I pulled one plug wire at a time to see if I had a bad cylinder and the motor continues running as I remove each one independently (had to check again.)

If I put my hand over part of the carb, say 50% or so it does improve the symptoms <u>somewhat</u> (could it just be a carb issue still?) It has a primer on it (pull it out and it goes back in on its own). I have tried pulling it out while the motor is missing / acting up and it does not seem to affect anything. If I push it in <u>all the way</u> (to what appears farther in than its normal resting spot) the symptoms get worse. Could my primer be an issue here? Or could the fuel pump diaphragm be leaking ? There are no visible leaks around the pump or primer. Could it be leaking into the exhaust hole? How do I see if my diaphragm is bad? Would the fuel line bulb remain hard if the diaphragm is bad? Oh my.

[ChampioNman]

You may want to look at the leaf petals (reeds) but I'd rebuild the fuel pump.

[mtkinzel]

Look at the leaf petals last night when I had the carb off (another soak and clean). I did replace them a few days ago and they still look ok.

For the fp.....I disconnected the line leading to the carb and squeezed the main fuel line bulb and gas came through. I reconnected that line and removed the fp from the housing (two screws). I again squeezed the the main fuel line bulb and the fp did not leak ( I was looking for fuel around the fp and out the rear hole but it did not leak) and the lines appeared to prime correctly.

I check the cam and butterfly sync with the throttle by eye and all appeard well.

Morning test: One gallon of fresh fuel mix with Stabil. Motor fired, idled well, NO<u></u> miss, hesitation, hiccup, burp, stumble. Well then I am thinking to myself. Ok, so what is causing these problems? I cut it off, let it sit. Repeat test three times. I can not get symptoms to appear. Cut off let it sit. One more try. With motor running correctly I use the PRIMER! and WA-LA! SYMPTOMS return. (I know, why would I do that? I have three kids that are always in this boat with me and they love tinkering. It is something they have done in pretending to be the captain.) SO............After pulling the primer out, symptoms re-appear and motor can not clear itself back to normal after 5 minutes. I cut it off and pull then push primer in and out - does not seem to have regular constant pressure (different feeling on different pulls/pushes). After doing this a bit I restart motor and symptoms have disappeared. So, in trying to UNDERSTAND if this IT, I prime it again while motor is purring well and again it fails to clear itself until I continue to push/pull primer into a position that feels like it has pressure.

Could this be it? Would a new primer be in order or just the four o-rings? I disassembled it and it seems rather simple. Rubber rings "look" ok but I know that is misleading. One seems flat as opposed to round. I am thinking there is hope still!

[ChampioNman]

I would replace the primer as it is almost 20 years old and isn't that expensive.

[mtkinzel]

Thanks again for helping me with this issue. I will know tomorrow morning about 7am the final results of my "experimenting" the minor issues with this motor.

Original Issues: Broken pull cord, loss of power, mid range miss/cough (nearly all at once.

I was lucky enough to benefit from these boards and others in doing many things for the first time. Compression and spark check for one or is that two?

New ignition coils, fuel pump kit, carb kit (and cleaned three times), primer soak and clean and replaced o rings, decarb, all fuel lines replaced, linc and sync, just to name a few.

After doing the fuel pump and finishing the primer about 2pm today I ran it on muffs an completed the same test as before and am happy to report it ran beautifully with no miss or issues at all. Like a new motor Tomorrow morning I will do a test run on the water but an confident problem solved. Thanks to all who chimed in and especially to ChampioNman!!!

One last question: I will be switching to XD-50 soon. Is a synthetic/blend rec. for the lower unit (if they even have it) also or should I stay with the traditional for this 91 2-stroke?

Have a great weekend.
Mark

[ChampioNman]

BRP Hi-vis is fine for your lower unit but if you want the good stuff buy the BRP HPF/XR. Good job and happy boating.