Lost performance on the way back...

Stonets

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Joined
Sep 27, 2015
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26
76 9.9 Evinrude.
Wield problem...going out plane the boat Okay, fish a bit on the way back felt like 2/3 of the power and can't plane anymore.

if unload some weight from boat tried again, it goes back to the same top speed.

brand new impeller and NGK 7BHS plugs. compression 112/114. Tested spark looks like top cylinder got less spark (jumps shorter compare to the one lower) and the top cylinder runs 200~300 rpm less than the lower cylinder.

checked 76 is the last model uses points and condenser. could this be something to do with the aged condenser/points so that the top cylinder misfire from time to time?? is it normal that one cylinder runs less RPM then the other?
 

Stonets

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Sep 27, 2015
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26
hey racerone, just to add how I tested the rpm. I unplug one boot and start the motor let it run on one cylinder to measure the RPM by tachometer tag on the other wire,after that do the same for the other cylinder. what I've got is at same throttle, top cylinder runs at 730RPM and lower cylinder runs at 930RPM. Is this normal or they have to be the same..? I did notice when the motor run on both cylinders the RPM goes to 2800RPM at the same throttle. my simple math doesn't work here or I'm really missing something here
 

kbait

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Nov 13, 2007
Messages
2,446
You have a points ignition motor. Service rhe points and report back.
 

fireman57

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Aug 24, 2004
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Wait wait wait. Are you saying that when you make it run on one cylinder that the rpms are different? Are you trying to add the rpms from the top and bottom cylinder to come up to 2800 at that throttle setting? That is not how that works. As you have figured out that engine will run on one cylinder. At least you have proven that you have spark on both cylinders. I would look at a fuel problem rather than points since you have spark. Maybe a high speed jet clogged with a piece of crud and it falls in and out of the jet. I have the exact same engine.
 

Stonets

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Sep 27, 2015
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26
thanks! will give a try...opening the flywheel is a totally outside my conform zone will need to figure that out.
I currently have 7BRHS on it, went out try to get the ones without R but only came back with 6BHS, told it is a hotter plug but should work...
 

Stonets

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Sep 27, 2015
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hey Fireman57, yes I figured that's probably how it works :). just confused why two cylinder runs on differnt RPM when given the same throttle. They both have sparks, however, top is weaker than lower, on the tester, top did reach 1/4 with blue sparks, but longer than that it becomes random, versus lower one has blue sparks all the way till more than 1/2 inch. I just suspect that when the motor is running with load the weaker top might misfire from time to time hence lower RPM and performance...just my theory or call it my guess :)
 

flyingscott

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Apr 8, 2014
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Are you using a 4 strk tach? Replace the points and condensors as set and use only BRP parts not aftermarket. Have you checked your coils?
 

82rude

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May 8, 2012
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4,082
1974-76 champion ul81c.Check your coils as flying scott recommended,even a hairline crack will cause no end of troubles.
 

Stonets

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Sep 27, 2015
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Flyingscott and 82rude, my tach has three modes it seems to be right when I used one of the modes. I did swapped the two coils and confirmed that it is not the coils as it is still the top got weaker spark and lower RPM, so yes I also suspect that it is the points and condensor kbait pointed out as well. something I haven't done previously so a bit reluctant to hammer the flywheel. I had champion on the previously then the 7BHRS now I will try with the new 6BHS plugs may be they will do some miracle...
 

Stonets

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Sep 27, 2015
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and what confused me the most is that going out not so much problem, but down graded performance on the way back...it did that in the past 3 trips already so that tells something, my guess again, could it be the warmed motor cause the aged condenser degraded as well??? I hate to open the flywheel, just feel like a big job to me :)
 

hardwater fisherman

Lieutenant Commander
Joined
Mar 19, 2010
Messages
1,725
Find yourself a factory service manual.... If you plan on keeping the motor you will need to learn how to service the ignition.... Or pay somebody shop rate to do it... And in some areas you may have a hard time to find somebody willing or able to work on older outboards...
 

fireman57

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Aug 24, 2004
Messages
3,811
Make sure you use the proper bolts on the flywheel puller.
Don't remember the thread size but you don't want to strip the flywheel holes. Get a decent puller, you can rent one at the auto store place. Basically it is a steering wheel puller. Do not use the three jawed ones as you can damage the teeth on the flywheel. Tighten it down and tap the top of the puller with a hammer as you increase the pressure. Don't whack it just gentle taps. If it doesn't come right off then let it sit with the pressure on it and try again in an hour or so. Changing points/condenser is a snap. Make sure you torque the flywheel back down to spec with a good torque wrench. For some reason 105 foot pounds comes to mind but don't trust my memory. look it up.
 

racerone

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Dec 28, 2013
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36,030
Well----105 FT-LBS is way too much.----How about 45 FT-LBS for that 9.9 model.
 

fireman57

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Aug 24, 2004
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Told him not to go by my memory. It is one thing even I don't trust anymore.
 
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