Loss of power in 1974 9.9 johnson?

[Gafisherman]

Hey guys,
I have a 9.9 johnson 74 model. The motor runs great cranks in 1-2 pulls from a cold start, but it can not plane out my 1448 lowe Jon boat. I have tried almost every hole position on the mounting bracket i found that two from the top will seem to give it some more power but will still not come over and plane. We tested it today with me, my friend and his dog. And gps says it only tops out around 11-12 mph, shouldnt it have more power for my boat especially with no gear in it. Not sure about compression i am going to check it in the morning when the parts place opens so i can get a tester. But both spark plugs are firing good spark they snap almost so i am at a loss.
thanks for the help

 

[Will Bark]

Re: Loss of power in 1974 9.9 johnson?

While you are at the parts place get an inductive timing light and carry it with you to the water check each spark to see if you are dropping spark when its under load.

 

[Daviet]

Re: Loss of power in 1974 9.9 johnson?

Is this engine new to you, has it preformed properly on your boat before?

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

It is new to me, the parts store was closed they guy went on vac. But we took it out thursday again i knoticed the flywheel is gettin real hot but the motor is stayin the normal temp and water is flowing out the back fine. i forgot to mention that last week i had it running on muffs and i took the top plug wire off while it was running and didnt knotice a difference but the when i removed the bottom wire it died as soon it was removed, but the top plug is firing when i pull the starter cord. Any thoughts or ideas, i have read on here that the motors will run fine on one cylinder but not have all the power.

 

[Rick.]

Re: Loss of power in 1974 9.9 johnson?

You should do a spark test with a tool that adjusts the spark gap to 3/8 of an inch( available at auto parts stores for about ten dollars). I doubt the upper is getting a strong enough spark. You will need to check your coils for cracks and also the condition of your points. Best of luck. Rick.

 

[nwcove]

Re: Loss of power in 1974 9.9 johnson?

im gunna take heat for this compression test without a tester,it wont give you real world numbers, but try it. remove the top plug, pull the cord out slowly pay close attention to the feel. now replace the top plug and remove the bottom plug, pull the cord slowly again. if theres a big difference in compression, you will definitely feel it!(does the top plug look wet after a run? ......compare both plugs after running, note any difference in appearance) the hot flywheel situation is new to me, but would like to get some info on that.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

ok ill try the compression in the morning. And i think everything is orignal on this motor, took the carb off last night to clean it and it still has a cork float. so i can only assume that the coils points and cond are all orignal as well.

 

[Rick.]

Re: Loss of power in 1974 9.9 johnson?

im gunna take heat for this compression test without a tester,it wont give you real world numbers, but try it. remove the top plug, pull the cord out slowly pay close attention to the feel. now replace the top plug and remove the bottom plug, pull the cord slowly again. if theres a big difference in compression, you will definitely feel it!(does the top plug look wet after a run? ......compare both plugs after running, note any difference in appearance) the hot flywheel situation is new to me, but would like to get some info on that.

I can't say for sure but a hot flywheel could be caused by a bad coil( arcing) We will have to wait till the flywheel comes off and see if there is an obvious problem. Rick.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

Ok its gonna be a lil reading but bare with me.

1. Compression today was 70 lbs on #1, and 70-75 on #2. this was when the motor was cold.
2. Checked my coils with spark tester am getting sparks on both wires.
3. Knoticed that my bottom coil wire was sparking through the top of the boot and arcing against the housing, while it was just laying there while i tested my top coil wire.
4. While running i removed the top coil wire and i was shocked when i touched the boot so i guess the fire is coming through it as well.
5. While running i took off the top coil wire and the motor died as soon as i removed it.
6. While running i removed the bottom coil wire and the motor still ran but you could hear the difference when i tried to rev it up, when i placed the bottom wire the power returned. So i guess its just running on the top?

7. i found long cracks in both of my coils on the side i filled them in with clear silicone but could not tell a difference.

So right now i am thinking either my wires are old and the spark is gettin through the insulation, i am planning on replacing the coils but just tryin to zero in on if that is the problem or not.

 

[nwcove]

Re: Loss of power in 1974 9.9 johnson?

I can't say for sure but a hot flywheel could be caused by a bad coil( arcing) We will have to wait till the flywheel comes off and see if there is an obvious problem. Rick.

good call rick! never thought of an arcing coil causing parts to heat up, but it makes perfect sense.
gafisher, if your coils are cracked, they definitely need replacing. you can buy metalic core .....and it has to be metalic core, wire cheap, by the foot. while your under the flywheel, points and condensors should also be replaced.....not a huge expense.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

I ordered my points and cond this morning, gonna try orderin the coils monday guess we will fnd out then whats up

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

would the cracked coils reduce the power of the motor? or is that still another issue

 

[Monte1961]

Re: Loss of power in 1974 9.9 johnson?

Yes. Spark to the plugs can be reduced significantly. Post back results and let us know how you make out.

 

[nwcove]

Re: Loss of power in 1974 9.9 johnson?

a "hot" blue spark is crucial to a motors performance! a plug can fire ......but is that fire getting "blown out " by the cylinder pressure?

 

[Rick.]

Re: Loss of power in 1974 9.9 johnson?

Have you heard the saying, " in for a penny, in for a pound"? This is no time to not change the plug wires and boots. Leaking spark will certainly affect performance whether it's through the coils or the wires. I'm not really pleased with your compression numbers but I expect it may well improve with use and/or a decarb. Rick.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

Ya I thought the comp could be better. I read in leeriys ramblings that rope starters can give lower compression reading since u can't turn the motor as fast. Also found the needle in the carb was missing the clip that holds it to the float. But I have my coils, carb kit, points and cond coming in the morning if nothing falls off the delivery truck .

 

[Monte1961]

Re: Loss of power in 1974 9.9 johnson?

That clip that is/was missing, was it in the carb or where? I gotta know! post back.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

i dont know, it prob wasnt even there to start with. the guy i bought the motor from, i dont think he knew what was going on with it. When i first got it the neutral stopper (keeps you from cranking it WOT) was in the wrong position and you couldnt even get the motor to rev over 1/2 throttle all i had to do was just adjust it.

 

[Gafisherman]

Re: Loss of power in 1974 9.9 johnson?

when i set the points, does the motor need to be WOT when i set them or does it matter?

 

[Daviet]

Re: Loss of power in 1974 9.9 johnson?

No, you can set them at the idle position.