Force 125 Compression

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
Comperssion test 145/95/85/175 wondering if it's worth rebuilding. Son just purchased the Bayliner 1987 w/ the Force 1987 125hp motor. The stator is shot, carbs need going through, lower end unknown. I ran the compression test three times each cylinder. Repeats within 5psig. A little baffled with the 175psig reading. Paid 2k boat motor trailer.
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Definitely need to remove head and take a look on how bad the cylinders are. To state the stator is shot is "vague" and should at least include resistance readings to validate such claim or even better voltage output readings. Lower unit can easily be diagnosed but only if the engine runs. Otherwise, opening and inspecting it is not worth the effort since it will required a total overhaul of the LU. Start with inspecting the cylinders first.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
The 2 middle pistons could be a bad gasket between the 2 pistons.
Tee bottom could be oil buildup in that cylinder.
The 145 is about the right #
Mine all read about 145 on all 6.
The important thing is all cylinders reading within 2-5# of each other.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Rebuilding is almost always worth doing as long as the engine is not totally scrap. With rebuilding you now have a KNOWN engine at probably less to equal cost of an equivalent used engine with unknown history. Couple that with the fact that Force parts are relatively inexpensive and Force engines are dirt simple --easy to work on.

For the most part you can do almost everything yourself.

As far as the lower unit, change the water pump impeller and gear oil. If the unit goes into both gears and neutral, leave it alone.
 

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
Stator resistance each blue to yellow wires reads open no resistance. Stator peek voltage blue to yellow wires less than 60v. Disconnected rectifier from stator no change in resistance or peek voltage. During wiring checks prior to stator troubleshooting found rectifier wired hot to grounding pin rectifier and ground to hot pin rectifier. Lifted stop switch wires white and blue from engine terminal strip. Retested stator resistance and peek voltage no change to resistance or peek voltage
 

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
You guys have a recommendation for service repair manual? I can't stand not knowing. I'm going to open and inspect and ride her still she throws me off. I'll be looking for that failed head gasket between 2 & 3 cyl's. And by the way I had to remove the 4 spark plugs to get the cranking speed up the check peek voltage. Using a new marine cranking/deep cycle battery. With spark plugs installed slow cranking speed with a hitch stall and recover.
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
The slow cranking could be a result of damaged piston rings. Again, removing the head and conducting inspection is the only way to go for now. If the stator's blue and yellow wires resistance is open then there should not be any voltage output from the same. The fact, you are getting output voltage there should be some kind of continuity on those yellow and blue wires meaning there should be some resistance. As for the charging system, if the hot wire output of the rectifier is connected directly to ground it will damage the rectifier leaving it as an open ckt thus it should not damage the charging coil of the stator. The resistance of the charging ckt is really low almost 0.5 ohms while the power ckt is between 680~800 ohms. Remember, the power ckt of the stator needs some good cranking speed to attain 180+ peak voltage if read on a DVA or 110~130 Volts RMS when read with a regular DVM.
 

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
Pulled the stator last night sitting on the work bench. I assumed the stator low voltage output durring cranking was residual floating voltage. Moving forward with the cylinder inspections. I'll circle back to the stator issue once I get a good look at the cylinder conditions. More to follow...
 

Jiggz

Captain
Joined
Oct 23, 2009
Messages
3,817
Just be careful there might be still be residual floating voltage in that stator.
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
The uneven compression causes slow turning for tests.
Remove the plugs and ground the leads for future tests
 

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
Pulled the head and removed the Pistons. Found all the piston rings still there but sticking in the groves. There is piston scuffing with transfer to cylinder walls. Mainly between the intake and exhaust port at 6 & 12 position. Cleaned the liner bores removing the piston material. Have a couple corrosion spots in liner wall. No 2 liner has a scuff through the exhaust port bridge. Going to measure out the liner bores next. Touch honed the cylinders last night. Visual looked okay except for No 2.
 

Longblock

Cadet
Joined
Jul 29, 2015
Messages
14
Block stamped 030. Changing Pistons w/ rings cyl's 1,2,&3. No. 4 piston going back in w/ new rings. Have not measured liner bores yet. Doing that next. I pulled rod caps through intake ports. Recovered all the rollers. Noticed roller cages shined up on the OD's. Is there a inspection for the roller races? Roller bearings look good clean no scoring or signs of heat. Rod journals look good just like out of the polish shop.

Any tricks going back together w/ rod caps through the intake. How do you keep the rod bearing rollers and races all together during the hole process?
 

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,924
No Title

Use assembly grease.
It flushes away quick.
Regular grease is too thick and might cause burnt bearings.
Bel-Ray
99030-CaB10 Assembly Lube, 10 oz. Brush Top

Maybe a weak magnet.
Try not to use a real strong magnet.
Even a weak magnet will make your parts a bit magnetic and stuff will stick to them.
 

Attachments

  • photo227119.jpg
    photo227119.jpg
    120 KB · Views: 0
Top