help with 25 hp johnson 1969 25R69B

[marceljigfisherman]

hello all
i am new to posting in forums so please forgive for newbie mistakes
i have been following several forums about my motors problem and possible causes so i will try to list everything i cant think of so here goes

1. motor starts and idles good
2. can run wide open for about 4.5 miles and then it starts missing and running rough and the rpms go down like it running about 1/2 to 2/3 open throttle. when it does this i can idle speed with no problems or missing.the 4.5 miles is a constant distance it has been doing this ( measurement comes from google earth).
3. things i have tried so far replaced hose on portable tank.
4. pump ball while it is acting up did not help. also pull out choke didn't help either
5. took cover off laid hands on head didn't feel extremely hot
6. pump ball up on tank at home it stayed hard for over 24 hrs.
7. took cap off tank made no difference (checking vent on cap)
8. have run seafoam in gas (double up on dosage a couple of times)
9. have run about 15 to 18 gallons of gas thru it since the middle of january thru april 19th
10. carburetor rebuilt about 6 years ago and new fuel pump about same time.
11. ran good last year problem started this year
12. changed plugs this year
13. look at plugs to day looks wet but not fouled
one question i have also can a condenser or coil being going bad when motor is running this long.
14.new hoses on carb and motor from about 6 years ago no signs of leaks under the cover
15. check the two pee hole below motor water coming out even when i rev motor more water comes out both holes
thank you all very much.

 

[racerone]

If coils are still original they are likely bad and cracked.----Or a coil / wire is shorting to ground.--------Pull flywheel to inspect.-----Just took a freebie 1970 18 HP apart today.----Was seized , got it turning then took the engine apart.---Scrap crankshaft and rods.-------Had 2 new coils in it already plus the big $$$ gear / bearing update in the lower unit.

 

[marceljigfisherman]

i have pulled flywheel this evening and will inspect them tommorrow thanks
oh and had to have that big high dollar gear worked on my outboard . the mechanic ground on it and it has been working good ever since.

 

[marceljigfisherman]

update on motor i have replaced coils,points and condenser
1. run boat about 9 miles up and back down lake
2. motor never quit or sputtered done good except i wasnt getting the rpms
3. only judging by sound and speed (use gps for mph )on rpms
4. got back to dock and run it and discovered that the butterfly wasnt opening all the way up
needed to adjust the set screw held it open by hand and the speed/rpms came up
5. also adjusted the low speed screw seems it was out of adjustment when starting .

question is now should i be looking for anything else that might make a difference since i have changed the coils and etc.
everthing is working okay just questioning about fine tuning,tips and tricks


thank you very much

 

[racerone]

Pound for pound it is one of the best motors you can own.------Lots of parts available both new and used.-----Adjust the low speed mixture screw for smooth idle and proper acceleration and you are good to go.

 

[marceljigfisherman]

thank you

 

[Crosbyman]

did you adjust for 0.020 on the high point of the cam lobe or better yet ..with a volt ohmeter meter

http://www.youtube.com/watch?v=ga1Cjymj6ms&feature=youtu.be

 

[marceljigfisherman]

high point of cam

 

[oldboat1]

The timing must advance along with opening of the throttle butterfly -- can't tell from your description whether that is happening. (known as the "link and sync" adjustment performed at the low end. At the high end, the throttle control cam should typically push the butterfly to full open.)

 

[marceljigfisherman]

the timing seems to be advancing the problem of low rpms was the butterfly was not opening all the way up it was out of adjustment i could move it by hand when running wot . when i was running it on the lake this morning at wot i move the butterfly to open up (didnt move it much) and the rpms came up to what seem like normal. i have since adjusted it and taken that out of it . hopefully this has me running at full speed again. the mph were about 20 at wot . it is on a 1448 lowes aluminum boat and loaded down with fishing gear and 2 batteries.and two trolling motors.

 

[marceljigfisherman]

also i watched the youtube vid thanks

 

[oldboat1]

Be aware that operating the throttle (i.e., opening the butterfly buy hand) independent of timing advance can damage the motor. Some of those videos show the butterfly being opened with a forefinger and the engine racing, as it will -- not wise.

 

[marceljigfisherman]

yes i agree