Force 75 threw a magnet at us

[Teseal]

I've already got the seafoam so I'm going to go head with that, next time I will get the Techron.

I disconnected the primer and plug the line to the carb but it did not make a difference.

I like the snake cam idea, I be looking for one right away.

 

[Redbarron%%]

Too bad you did not need a flywheel while I had a new style I was trying to fit on an early engine.
No one wanted it and I sold it cheap on eBay.
Water under the bridge...
If swapping the coils made no difference and each cylinder has good spark then I and the compression is equal and good on all cylinders I would pull the carb adapter and take a good look at the reeds.

 

[Teseal]

I will inspect the reed valves, running the seafoam thro it now

 

[Teseal]

“And the plot thickens”. Found something interesting during the seafoam run. The boat we put this motor on had a temp gauge so I put a sender on the motor, there were other concerns at the time so I kinda forgot about testing/calibrating the temp gauge. Unfortunately this lead to ignoring it completely. Someone else babysat the motor for the seafoam run for me. On the last cycle I checked on it and notice standing by the motor the temp gauge was somewhere less than 100 degrees, probably 75. The hose was supplying water at I would guess 60 degees. So I put my hand on the power head just behind the thermo housing with it running and the head was cold. The motor was finishing the last run cycle and burning the remaining gas so it had been running over 20 minutes. My first thought, there was no thermostat. There was a thermostat but it had pinch in its seal small shreds of rubber, looked almost like drill fillings. I could blow thro the thermostat. Cleaned and tested with hot water and it did open fine. Also tested the boat temp gauge the same way and it work. Reinstalled and test ran, the water temp never came up. Thermo is 130 degrees. Any idea what’s keeping the motor from warming up if the thermo is working?

I am ordering a new thermostat.

Also I did try one of the 2 tachs that did not work on the regulator output on the AC output and it did work.

Still need to inspect the reeds, waiting for the snake cam.

 

[pnwboat]

There should be a spring under the thermostat housing that holds the thermostat against the horse shoe shaped spacer and rubber thermostat seal. If any water is leaking past the thermostat seal, you may get a low reading.
If everything looks OK, I'm not sure I'd worry too much about the temperature at this time of year. Considering the incoming water temp was low, what you're seeing might be normal. Since the cooling system is not a sealed pressurized system like in a car, it's not going to behave exactly like what you see in a temp gauge in a car.
The most important thing is that the motor is not over-heating.

As far as the tach issue...did you check it right at the new regulator, or were you using any of the existing wiring harness.

When ever I install the regulator that has the two red wires, and the wiring harness only has a single connection, I always tie the two red wires from the regulator together. Don't know if that makes any difference. I would think that they should be the same.

As far as the charging voltage, you won't see any increase in voltage until the motor gets up to about 1500 or 2500 RPM for about 5 to 10 seconds. Then you should see anywhere from 13.5 to 14.5 volts DC at the battery. If you are seeing just fully charged battery voltage 12.5-12.7 volts DC while at 1500 to 2500 RPM's, then I would suspect the charging system is not working. Either the charging voltage from the stator to the regulator is not good, or the regulator is bad.

 

[Teseal]

There is a spring and the rubber seal looks fine and for sure the motor is not overheating.
The wiring in the boat had previously been replaced. Before and after replacing the regulator a second tach was installed directly to the regulator and did not respond. When the second tach was wired to the AC it did work. I need to try the tach in the dash connected to the AC. I will check the wiring also.

OK I understand the charging situation and haven't monitored it at a condition as you said where it should be charging, the battery is up and in good shape.

If the reed valves all look good I guess I'm back to the flywheel.

Thx for your comments, they sure are appreciated!

 

[Teseal]

The tach wiring checked out ok but haven't tested the in dash tach hooked to the AC yet. I don't see a problem with the reed valves. Guess I'll start looking for a flywheel.

 

[jerryjerry05]

If the tach is the wrong or bad it can cause a no spark
situation.

 

[Teseal]

Ok I did find a flywheel I could afford, actually a flywheel, stator, and trigger for $150. Be a few days before I get it on the motor and I'll update then.
Thx jerryjerry, I did think that a bad tach could bother the ignition so we tested previously with it disconnected but there was no difference.

 

[Teseal]

Finally got some decent weather to test the 75. Put in the new (used) flywheel and stator and tested on the hose. I did not see a difference, very rough idle, rpm oscillating a bit, with vibration (so that eliminates the flywheel balance I suspected), noticeable miss from idle to about 2.5K where I tend to stop on the hose. Also received a trigger ckt with the flywheel so tried that next. Still a rough idle with vibration but did not notice the unstable rpm nor the miss. Seemed to increase to about 2.5krpm without missing and sounded smooth. I want to lake test next to see about power and how it responses pushing my bass boat. I have hope with the lake test but still wonder about the vibration at idle. Possible it is just the right freq to resonate with the boat, idled out of gear about 1050-1150 rpm. Be awhile now before I can lake test, even in KY here we got some cooler weather, snow on the ground today.
I did get the tach to work by running it off of the AC output as suggested rather than the regulator output, thinking maybe the regulator is suppling a DC voltage reference rather than a pulse for the tach. (?)
I will follow up and still am open to any comments or suggestions, this may not be over yet. Thx for all your attention.

 

[legalfee]

Finally got some decent weather to test the 75. Put in the new (used) flywheel and stator and tested on the hose. I did not see a difference, very rough idle, rpm oscillating a bit, with vibration (so that eliminates the flywheel balance I suspected), noticeable miss from idle to about 2.5K where I tend to stop on the hose. Also received a trigger ckt with the flywheel so tried that next. Still a rough idle with vibration but did not notice the unstable rpm nor the miss. Seemed to increase to about 2.5krpm without missing and sounded smooth. I want to lake test next to see about power and how it responses pushing my bass boat. I have hope with the lake test but still wonder about the vibration at idle. Possible it is just the right freq to resonate with the boat, idled out of gear about 1050-1150 rpm. Be awhile now before I can lake test, even in KY here we got some cooler weather, snow on the ground today.
I did get the tach to work by running it off of the AC output as suggested rather than the regulator output, thinking maybe the regulator is suppling a DC voltage reference rather than a pulse for the tach. (?)
I will follow up and still am open to any comments or suggestions, this may not be over yet. Thx for all your attention.

One suggestion I have is to get a CDI rectifier / regulator. I had ordered some cheap RRs and my tach was either jumping around or dead. Got a new CDI and my tach works like a charm.

 

[Redbarron%%]

It is possible that if your timing light flashes along with the higher rpm your problem could be with dirty carbs that are not delivering fuel correctly from above the idle feed at low airflow and the main jet at higher air flow at higher RPM.

 

[Teseal]

MERRY XMAS ALL !
Ok Redbarron I follow that, you suggest something with the carb idle ckt? The single carb has been removed and cleaned, but I can check it again. The darn motor is running smoother so leaning towards a mechanical situation. That's another reason I felt the new (used) flywheel would make a difference, but it did not.
Just for the sake of conversation, anyone ever had a motor somehow out of "balance" that caused a noticeable vibration, and were there additional symptoms?

 

[Redbarron%%]

If it idles OK and runs at high speed ok the transition from idle to the main jets would be n question.
I am not familiar with the 75 HP, but most of the later Force/Mercury run in idle to some RPM and then transition to the main jets. If the jets are dirty or the idle circuits are then they may not blend and crossover smoothly as you accelerate the engine.
As to the vibration in the engine did you have any magnets missing or chunks broken out? I would inspect it fairly carefully when you have it off next time. If you had a cone or something like a plumb bob you could hang it by the string and see if it balances statically.

 

[jerryjerry05]

The 3cyl. Forces: none really idle what you'd call smooth.
The air/ fuel mix screw controls the operation up till
about 2k, where's the screw set at now?
They suggest 1 -1 1/2 out from lightly seated but that might
not apply to your motor???
One customers motor needed to be set at 3 full turns out to
just idle.

You do the starting fluid test? A small air leak/ bad port
cover gasket can affect the idle and burn up a cylinder.

 

[Teseal]

If I remember right the idle mix screw is set about 1/2 turn. Before replacing most of the electronics one of the symptoms was the idle mix had very little effect on the idle until it was just about closed. It does have more influence now but the 1/2 turn was the best results. Didn't like it much because it would make you think the motor would be running lean.
I have not done the leak test. Where exactly would you spray the fluid?

 

[jerryjerry05]

1/2 turn. Probably not right???
Procedure for setting the air screw.
Set at 1 1/2 turn out.
In the water, in gear turn the screw in 1/8th a turn.
Wait 10 seconds, then turn again 1/8th and wait 10 seconds.
Repeat this until the motor bucks, kicks, stutters etc.
Then turn out 1/2 turn. This should be where it should run
right.

 

[Teseal]

Follow up: Had the 75 out on the lake the other day to see where we were at. It was unusual that it didn’t start right away but it wasn’t the problem. The starter was dropping out as soon as the motor would pop the starter gear dropped, the starter would continue to spin but the gear was not engaged, had to switch off and retry. I did prior to the lake test increase the idle mixture so we were out a little more than one turn after adjusting. I didn’t realize before that the single carb on it the 75 has an intermediate orifice that is also controlled by the idle mixture jet. As the carb plate opens to mid it uncovers a second orfice. Motor fired up and still vibrated at idle and more than I would expect at mid range, 2-2.5k but really screamed above that. It pushed the 17’ bass boat with 2 people over 30 mph. Tach is working fine WOT was only 4200rpm, but I have no idea what the prop is so I was satisfied.

I did read at several places where there were opinions that the 3 cycle motors didn’t idle very smooth, agreeing with you JerryJerry, so for now I am writing it of as vibration that most probably is resonating with the boat and becoming amplified. Should I learn more I let you all know. Thx much for all of your input helping out with this beast, much appreciated. Be Safe THX