81 evinrude 25rcim running eratic & unpredictible HELP

[power drifter]

1981 well aged 25hp evinrude rope start that is on my power drifter, this thing is unpredictible but always trys & starts within a couple pulls even with temps in the teens, biggest problem is once started it revs fine in neutral but once in gear acts bogged down and wont come onto plane, coughs and sneezes a couple times then when least expected it takes off to the race and once running relatively normal at WOT it will begin to slow down approx 15% after a mile or so, replaced all fuel lines, new fuel pump, new plugs, cleaned carb ( just cleaned again and found small fabric thread in jet) ( just ordered new carb kit to do extensive cleaning) it is also slowing down at wot.... engaging the choke makes it fall on its face and pumping the primer bulb deepens the exhaust sound but neglidgeable difference in speed. i believe multiple issues are at play, lean squeeze due to partial blockage, but also suspect electrical. Tested the ignition coils with multimeter ( not sure what im looking for or at ) but one ignition coil registered resistance and the other NONE, ZIP, ZERO, removed kill switch lead and had same results. could it be power pack, how to test? the motor used to push the power drifter in the middle 30mph now middle 20's and it using fuel like its a 125hp

 

[nwcove]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

welcome to iboats power drifter!! jmo, but you may still have a fuel pump issue if the motor is going through fuel like crazy and pumping the bulb changes the engine "note". but, dont go out and buy a pump on my advice, other members will chime in with other opinions and experiences.

 

[boobie]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

Do a cyl drop test on it when it's running and see if it's running on both cyl's.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

carb kit will be here friday and ill do the drop cyl test. i presume it is running on both at least part of the time (when on plane)) but concerned you are correct and intermingle dropping a cyl./ but not sure. at rest it sounds fine and is responsive (other than the squeeze) which i hope to remedy friday. under a load its bogging bad.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

ok, went through the carb with the rebuild kit with new float and valve, popped out all the carb plugs and checked ports etc. put new ingnition coils and spark plug wires ( just prev gapped and put new plugs in). did find badly corroded internal plug wire connection that could be attributed to a weak spark.... put a water hose the motor started great ( initially a couple sharp pops) then sounded and ran much better with no sneezing through the carb. I set low speed jet at 1 and 1/2 turns after seating ( will adjust on the water after it i put a load on the motor and it warms up). the bogging issue has yet been explored. ill know tomorrow...................... any tips or advice on fine tuning the carb would be much appreciated. ...... Also found that some water has entered the lower unit gear oil case, which gasket should i purchase to resolve this issue.........

 

[jasper60103]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

Congrats on progress.

There are instructions for fine tuning your carb in the Top Secret Files sticky on top of
the forum page.

Regarding the LU. First change the drain/fill plug gaskets and see if it resolves the
water intrusion.

 

[series60]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

Also found that some water has entered the lower unit gear oil case, which gasket should i purchase to resolve this issue.

Hard to say which gasket to replace until we know which one is leaking. I would suggest doing a pressure test to determine where the leak is. You'll need to buy a LU rebuild kit in any case. Read everything here about rebuilding the LU on your motor. Most smaller omc/brp outboards are similar and very simple in form and function. Biggest issue usually is removing the brass bushing for the shift shaft. Search function is your best friend here.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

took the boat out yesterday and it had the exact same symptoms as before. sneezing through the carb and bogging like it getting too much fuel. So im back to square one. ANY IDEAS? After the motor got warm it seemed to run worse. the fuel pump is ( seems to be ) working well and if i forget to open the port on the fuel tank it will moderately indent the plastic tank from the vaccum. Once i resolve the running issue i will tackle the lower unit.

 

[AlTn]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

you've tested with the kill switch wire removed from the powerpack..you've replaced both coils and plug wires < assuming you've already replaced and checked the sparkplugs>...if it's an ignition problem, then the powerpack is the next most likely source...unless there's a bare, or broken internally wire, from the trigger or power coil under the flywheel < unlikely, but possible > nothing under the flywheel will affect one cylinder and not the other on a two clylinder CD ignition...you can go to the troubleshooting guide at cdielectronics.com for the testing procedures..note: you'll need a dva adapter for your multimeter, or a multimeter that already has this feature

 

[nwcove]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

sure sounds like its still fuel related, but you could remove the powerpack and clean the ground wire and its contact point just for a try.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

ok, had a bit of time today. did drop cyl test, TOP CYL NOT FIRING & NOT GETTING SPARK. Bottom Cyl running like a top... double & triple checked different plugs, plug wires etc. So i swapped the new ignition coil wires ( between power pack and coils) and the spark moved to the top coil. i believe this rules out the new ignition coils i put on. REDO on the compression check correctly and glad to see 121 & 120. ....... at this point it strongly looks like the power pack is sending spark down one wire (to ignition coil) and not the other...... (side bar.... as the bottom cyl was running i had the top cyl plug held against the block and saw a couple sparks from the plug, then nothing. Looked as if the spark was rarely intermittent ....................... WOULD THIS IN FACT BE A BAD POWER PACK OR FURTHER UP THE THE LINE

 

[nwcove]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

you did the compression test with the motor running??? not a valid test, and probably filled your tester full of fuel. check the ground wire connections for corrosion at the block, and do a proper compression test.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

checked ground wire and its clean and correct..

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

redo on the compression check, 121 on bottom and 120 on the top.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

is it possible that the power pack could provide spark to one coil via spark plug and not the other

 

[AlTn]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

yes

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

EUREKA.. IT WAS THE POWER PACK. I PROBABLY COULD HAVE GOTTEN AWAY WITHOUT PUTTING THE NEW COILS ON, but it a 32 yr old motor and its worth not being broke down. both cyl firing like a new one, starts better, easier and quicker. now knowing its operational and worth additional repairs ill start on the lower unit and see where the water is coming in from. Thanks for all that contributed. much appreciated.

 

[power drifter]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

postscript;

 

[nwcove]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

EUREKA.. IT WAS THE POWER PACK. I PROBABLY COULD HAVE GOTTEN AWAY WITHOUT PUTTING THE NEW COILS ON, but it a 32 yr old motor and its worth not being broke down. both cyl firing like a new one, starts better, easier and quicker. now knowing its operational and worth additional repairs ill start on the lower unit and see where the water is coming in from. Thanks for all that contributed. much appreciated.

congrats power drifter!!! and just a piece of advice now that its running well. if you have to do any other trouble shooting in the future, never crank the motor over without the plug wires grounded to the block, those cdi ignitions dont enjoy it.

 

[jasper60103]

Re: 81 evinrude 25rcim running eratic & unpredictible HELP

EUREKA.. IT WAS THE POWER PACK. I PROBABLY COULD HAVE GOTTEN AWAY WITHOUT PUTTING THE NEW COILS ON, but it a 32 yr old motor and its worth not being broke down. both cyl firing like a new one, starts better, easier and quicker. now knowing its operational and worth additional repairs ill start on the lower unit and see where the water is coming in from. Thanks for all that contributed. much appreciated.

Congrats.
I have a copy of the Lower Unit section of the OEM service manual.
Send me a PM with your email address if you would like a copy.