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1989 50 HP Force Voltage Drop

bbar97

Member
Hey everyone,

I've been working on this engine for years on and off in my freetime, and I'm learning as I go. Yes, years. Every time I make progress, I run into another problem, but i'm not stopping until my engine is purring.

Heres the current problem. When I try to start the engine my starter spins, and turns the flywheel, but doesn't turn it very quickly. It turns about 3/4 of a full rotation, then struggles to go the last 1/4 of the way (I guess because its harder to turn as the pistons are compressing) and then the cycle starts again. I've recognized the problem as a voltage drop, and in troubleshooting i've replace my battery, battery cables, and starter solenoid.

Before those replacements, I was getting a drop of about 12.6 v down to 8ish volts upon turning the key, and with each subsequent replacement and cleaning of wires over time, the voltage would inch up by half a volt of so. I'm now at about 9.8v. I'm measuring this voltage at the starter solenoid on the post the battery is connected to. For the life of me I can't figure out what is causing the drop. Every component up to the point im measuring is new.

Could it be the other wires that are connected to the starter solenoid? Theres the wire that sends the starting signal to the post the battery is connected to, theres a wire (called the interlock switch wire apparently) thats on a side post, and theres the cable that goes to the starter itself. Theres a tiny bit of corrosion on the starter cable, but it doesn't seem too bad and I was thinking it couldn't be the problem because I was testing the flow before the current reached that point. Now I'm starting to be more suspicious of that thought. If its not that, does anyone have any thought as to what it could be? (Also I forgot to mention that the starter itself is new as well.)
 
Very FIRST thing you do is a compression test.
The uneven comp on one cyl. can do exactly
what you describe.

The gearcase: if the bearings are corroded??
Then it can do this too :(

Lastly the battery if it has a dead cell?
Or the cables bad or not grounded or
the connections not tight.
Again the same problem.

Post the compression results???
 
Thanks for the reply Jerry,

I did a compression test and the results were kind of inconsistent, but the average for each one was around:

Top Cylinder: 75PSI
Bottom Cylinder: 60 PSI

It may have been a fluke but on one of the first tests I did on the top cylinder, I got two or three full, fast flywheel rotations and the PSI gauge read approx. 125 PSI, but I couldn't replicate it.
 
How was the test performed?
You need to remove both plugs and
use a screw in type pressure tester.
Push the throttle all the way forward.
If you use the key to turn the motor
over? the plug leads need to be
grounded and the Neutral safety
switch jumpered.
I added a pic of the octopus I made
for grounding the plug leads.

Easiest way: If you use the solenoid and jump it
from there, you don't need the octopus
or ground the leads.
 

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For the test I unscrewed both plugs, and used a screw in compression tester.

I'm not sure if this was implied well enough in my OP, but the engine doesn't run.

Do I push the throttle forward while I'm turning the key? I thought the controls had to be in neutral to start? Is that what jumpering the neutral safety switch allows for?
 
Throttle all the way forward and yes jumping
the N safety allows the key to be used.
Very important to ground the plug wires.
They say that you can blow the packs if the
leads aren't grounded.
Or jump it at the solenoid.
That way the plug wires don't need to be grounded.
The throttle all the way forward doesn't really
need too done either(my opinion) it makes no
difference.
If the readings aren't above 125 on one cyl?
Then find another gauge and try again.
 
Don't forget the negative side connections while looking for your voltage drop....another thing to consider is making voltage drop measurements across each item in the high current (starter circuits) paths. Using a single reference point will help in eliminating false measurements.
 
Putting aside the compression problem for now, I can't for the life of me figure out what is causing the voltage drop.

I have replaced nearly every single component involved in the starter circuit. To date, I have replaced the: Battery, battery cables, Starter Solenoid, solenoid ground wire, wire harness, Starter cables, and rectifier. The only two things I could think of that could be causing the issue are the starter's brushes, and some kind of bad connection in the forward control box related to the ignition wire.

I replaced the starter around a year ago, and I recently took it apart because I thought it could be the cause of a separate issue I was having, and I had a lot of difficulty getting the brushes back in. Not sure why its designed like this, but there are four magnetic "brushes" in the bottom, and you have to get them all in their respective holes while simultaneously putting the cap back on, and if you let go of a single one of the brushes you have to start over. It took me like an hour and a half to get the cap back on and i'm not 100% sure the brushes stayed in place. Could loose brushes cause the voltage drop?
 
I use electrical tape to secure the brushes in place.
A piece of tape(2) about 10" long.

If you turn the key to start the motor?
The voltage should drop down to 8-9v.
That's just normal draw.

You need to remove all the plugs to do a compression
test right.
 
Ok I re-did the compression test and both cylinders are showing 60 PSI consistently. I removed both plugs for the testing and I used a screw in tester. Could 60 PSI cause a lack of ignition?
 
60# is WAY!!!! low. But since both are at 60# I'd say the gauge is probably at fault??? Re-test with another gauge.
Harbor Freight tools are not recommended for these tests :(

Both plugs out, throttle advanced to wide open, jump at the solenoid, key OFF!!
IF??? it still shows 60# then you might have a bad head gasket???

Turning too slow: can cause a no spark condition, check the starter and battery and inspect the battery cables for soft,
weak spots, load test the battery, get a hygrometer and test each cell, the battery can still test 12v and still have a bad cell.
 
Recently I've begun applying my points and condenser replacement skills to a 1985 Force 50 that my daughter just bought. I was surprised to see after adjustment that the points don't close until not a whole long while before they should open again. The engine start and idle timing is dependent on the proper gap of the points. If they are wider than they should be then that means they are opening earlier than they should. The simple test to see if an early spark is behind your sudden engine crank slow down problem is to disconnect the plug wires.

Assuming the issue remains since your compression test is done without plugs and you probably turned it over with no plug or compression test gauge attached then failure to deliver enough amps is ordinarily the problem but you've replaced all the usual suspect areas. Maybe loosen the starter mounting bolts just a little to see if there is some binding with an out of round flywheel otherwise there is binding (bent shaft) before the case (where it free spins when in neutral) or a faulty component you've already replaced. Assuming you couldn't detect any binding during the compression test you're back with some faulty component you've already replaced because even though the compression is uneven between the 2 cylinders, it should be easy for that honking starter to turn it over. I've seen starters on 6cyl automotive engines that ain't any bigger.
 
In his last post he said the comp was even but low.
His 1989 50 has electronic ignition. No points.

The size of the starter and the engineering in the 2 different starters.
The outboard starter is something designed/engineered to do a minimum job.
The automotive one that's the same size is engineered to turn at higher resistance.
I saw the starter on a big block Chevy that was TINY!! It's all in the design and engineering.
 
Ok i'm in the process of looking for another gauge, there seem to be a lot of cheap ones.

In the meantime, here is a video of the flywheel spinning quickly with both plugs out, and struggling with both sparkplugs in. Isn't it strange that I could have low compression but have strong enough compression that the starter struggles to turn the flywheel quickly?

https://youtu.be/MEzjHqyUmPg
 
Hey Jerryjerry05, I've made a lot of progress finally, and I can get my starter to spin the flywheel really fast even with the plugs in, and I have confirmed I get a spark on both coils.

I also re-did the compression test, and now that I'm getting sufficient spin on the flywheel I am getting really good compression (150 psi on both cylinders) . So, I am now getting spark and compression, but its still not starting, so I think either fuel or timing is my issue now. I replaced my old gas with new gas, and can confirm its getting to the carb bowl, but the spark plugs are dry when I check them, so I suspect it may not be getting from the carb to the cylinders. Also, a long time ago I removed the flywheel a couple times, so its possible I messed up the timing somehow.

I recently cleaned the carb and replaced the gaskets on the carb, but maybe I missed one of the valves?

Yesterday I sprayed starter fluid in the spark plug holes and in the carb throat, (I now know I shouldn't be using starter fluid on a two stroke) and it resulted in an extremely loud backfire. Any ideas on where I should start the troubleshooting?
 
A loud backfire could be the carb is flooded and along with the SF it just exploded.
Now to check the results of the backfire: one tiny backfire or cough can blow a hole in the fuel pumps diaphragm or blow the port cover gaskets and result in sucking air??
Like racer suggested: check the flywheel?
You using the choke when attempting to start? you have to hold the key in as the motor turns over, just pushing it in for a second does nothing.
The amount of gas on the plugs is very minimal and almost invisible.
 
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Oh, its very possible that I had the coil leads on backwards... I'll make sure to check to be sure they're on right. What should I be checking for with the flywheel key? And can I see it without removing the flywheel?

I am indeed using the choke. I didn't realize that pushing the key in engages the choke until a few days ago, but I was visually confirming that the choke was working while I turned the key.
 
Choke: the key needs to be held in as long as your turning the key, otherwise the choke just flips up and down doing nothing.

Flywheel: Your testing for TDC and flywheel key position.
Plugs out, insert a long screwdriver in top hole, turn the flywheel slowly and watch as the screwy gets pushed out to the max.
Then front top of the carbs and flywheel is an indicator showing #1 piston is matching the mark on the indicator and flywheel.
Flywheel has marks indicating #1 #2
 
Great news! Yesterday after around 7 years of working on this engine on and off (with varying levels of motivation) I finally got it to start! Thanks to Jerry (and others) for all the help, its much appreciated.

I took the carb off and cleaned and boiled it, but the problem may have been the idle needle (or air needle?) on the top. I've taken the carb off a few times before, and its very likely that when I took the screw out I just screwed it back snugly without realizing how it works, so this time I tightened it gently, then went one turn out.

She now starts and sounds great, but I didn't have a container with water set up so I didn't want to run it for more than a few seconds. When I get a chance I'll get that set up so I can test revving it up and fix any issues with idling or revving as they come up.

I'll definitely need to fine tune the gear selection, as it didn't seem to be switching until I pushed the control all the way forward or all the way in reverse. I'm also going to need to figure out the tilt/trim system and a few other small things.
 
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It's the little things that mean a lot!!(I think that was in a song??)
Cleaning a carb and then setting the air screw is just something that I just do as part of the job.
I bet you won't do that again.
The muffs for your 50 are different than ones that fit the bigger motors.
 

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Ah, dang - so I can still get it to start, but apparently it dies quickly when no longer choked, and while it is choked it lasts a little longer but dies after around 20-30 seconds. I've tried various configurations of the air screw with slightly different results. It also doesn't start on its own every single time, but if I use starting fluid it starts every time.

Here are some possible culprits:
-Small pinholes in the carb throat could still be clogged after cleaning multiple times and boiling it?
-Could have an issue with the fuel hose where it connects to the fuel tank. I saw an issue where someone noticed the valve got stuck. I have the gray hose/bulb a lot of people seem to have now.
-Carb float could be getting stuck?
-I don't have the steering bar attached to the engine mount, which lets the engine vibrate a little bit I think. Not sure how likely this one is.
-The engine doesn't pee, so either the water cooling lines are clogged or I just didn't have the water level high enough above the intake in the bin of water I was using.

I do have the correct muffs to use with a hose, but unfortunately my boat is in an apartment complex parking lot so the only water hose I could use is the one from the car washing station. If it would be worth the effort of trailering my boat back and forth to that station I can probably do that, but if I can use a bin of water just as easily I would prefer that option.

Thoughts on the most likely problem?
 
If you use a bin? Then make sure the cavitation plate is 4-5 inches under water.
These pumps aren't self priming but once they start pumping they can run in low water in a bin.

Stalling after starting: that sounds like a fuel pump issue or the fuel line is sucking air , maybe the floats stuck?
The best way is remove all inline connectors and run the hose direct from the tank.
The 89-50 didn't have a pee tube installed from the factory, did you install one?
Most of the exhaust comes out the snout under the cavitation plate.

The air screw: set at 1 1/2 turn out and then once it's running on it's own you can adjust from there.
 
It was indeed a fuel pump issue. I replaced the fuel pump diaphragm and diaphragm gasket and a small valve gasket, and it started up without any issues on the first try! It looks like the next step for me is to get all of the accessories' wiring and the tilt trim figured out. Thanks for your help!
 
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