1993 tracker Johnson 90 hp losing power and stalling

[Blackhawkdriver]

I have a 93 Johnson TJ90TLBTS outboard motor just recently purchased. It starts up idles and shifts just fine. It would run great for 20 minutes or so. Running any where from 1/2 to 3/4 throttle for about 20 minutes. It would bog way down and die. It it did this three or four times. Then the starter fried. Motor will still turn with good compression. It has new fuel lines. Any ideals. Water pump is working fine. Spark plugs are giving good spark.

 

[Blackhawkdriver]

Any ideals?

 

[emdsapmgr]

Probably an ignition component failure. Weak ignition components tend to fail once the engine heats up to normal operating temps. (It may run just fine when the engine is cold.) Could be a power pack, stator or even a timer base. Check for spark on each cylinder when the engine starts to slow. Fortunately, that engine has two power packs, one controlling the spark to each head. If you find one plug with no spark, swap the power packs and see if the "no spark" problem moves to the other head. If so, replace the bad power pack.

 

[Blackhawkdriver]

Thanks.... Today finally got it restarted. Cleaned carbs again, emptied tank pressure tested tank, check pump, and cleaned all fuel lines. I let the engine warm up and the set the throttle back to just past half way. Ran great for a while the stalled out again. Acts like engine was seizing up....so I got the compression tester out again. Few days ago I tested it. Number 1 was at 110, # 2 was at 100, 3# 100, 4# 105. Today after it stalled I retested #1 60, #2 65, #3 90, 4# 70. Frustration. I checked the spark on each cylinder after it stalled and all spark was present and strong. I'm think I'll be looking at a rebuild. I never rebuild a boat motor. I've rebuild car and Diesel engines imagine not that much different.

 

[emdsapmgr]

Possible the engine suffered an overheat lockup. Once the engine overheats, the pistons can swell and eventually stick inside the cylinders. This is a fairly rare failure-esp since you had no overheat warning horn. Repeated overheats like this will damage the rings and will quickly result in low compression. Was the telltale functioning properly on the engine? Pull the head and check the placement of the 4 rubber water deflectors by each cylinder. If you have a strong water pump impeller and these rubber deflectors are out of position (or clogged with sand, salt, etc,) the engine can overheat internally and may not sound the warning horn. Also, pull the water passage cover off the head and check it for blockages.

 

[Blackhawkdriver]

Well just to keep everyone informed. I rebuilt the carbs again. I put new plugs in. Decarbed the cylinders, Flushed the cooling lines installed new thermostats. Put new power pack on, starter, and solenoid. Fired her up she purred like a happy kitten. Water pressure was 100% improvement. idle temperature with the heat gun on the heads where 140 degrees. Pressure on all the cylinders where all around 105. Put a new prop on it got it to the lake.

She was a little bit hard but got her started. The we idled around for a good thirty minutes with no issues. Heat gun on the heads showed 150 degrees. 1/3 throttle increase cruised around for a good 15 minutes. Heat gun reading on the heads 160 degrees. Only issue we have had to this point was the new four blade prop acted alike it has no reverse. It would not move the boat at all.

So we increased the throttle to 2/3 move along real good. The four blade prop moving us right along. temp at the heads still 160 degrees water pressure is good. I'm beginning to get a warm a fuzzy that we got the thing running good. I'm in 60 feet of water. still at 2/3 throttle. All of a sudden it acted like I hit something. The motor starts clucking. temp with heat gun reads 168 stable. The the motor dies. temp raises a little after shutting down but not past 180 degrees.

I raise the motor look for damage. Zero nothing. Prop doesn't even have a scratch. Put the motor back down and attempt to restart. Motor won't even turn over. Locked up tighter than... So pull out the trolling motor reload the boat and drive the hour and half back to the house. Motor still locked up.

I drain the lower unit (just changed the oil last week). I find chucks of metal on the magnet drain plugs. metal shaving in the oil. I'm sure that the lower unit is locked up. I pull the lower unit off. It seems to turn fine now. The motor seems to turn fine now. So Take the lower unit apart. Zero damage. No bearings damaged. No teeth damage. No wall damage. Nothing, but still finding small metal shaving in housing. Yet their is zero visible damage. I've got the this 100% apart.

Now got to put it back together. Time to search the forms for clues and hints.

 

[racerone]

Is oil inmjection in service and confirmed to be working properly ?----Or is it bypassed and you need to mix at 50:1 on that motor ?

 

[Blackhawkdriver]

The oil mixture VRO seems to be working. I marked it with a marker and it is using the oil

 

[Blackhawkdriver]

The oil mixture VRO seems to be working. I marked it with a marker and it is using the oil

 

[emdsapmgr]

I've seen a 200 hp V6 lockup tight with no warning horn. When disassembled, there was a significant carbon ring around the skirt of all the pistons. The carbon ring was thick enough that it prevented the incoming fuel/oil mixture from getting to the back side of the rings to cool them. Engine never overheated, (no warning horn) but the rings got so hot they overheated the piston and locked it up in the cyl at about 4000 rpm's. Cracked one of the port bridges-the block was scrap. Two pistons had significant The carbon ring came from using a non-factory oil-also the engine had never been through a decarb procedure. The carbon ring took 5 summers to appear from a new overhaul. You might want to pull a couple of bypass covers off and inspect the ringsets and piston skirts. Maybe even a head...

 

[Blackhawkdriver]

I've removed the bypass covers. Their was no evidence of carbon build up. I do however to tear down the engine once I figure out if my lower unit only requires a seal kit to re assembly. Everything thing in the lower unit besides the seals looks to be in excellent condition.

 

[Blackhawkdriver]

I've removed the bypass covers. Their was no evidence of carbon build up. I do however to tear down the engine once I figure out if my lower unit only requires a seal kit to re assembly. Everything thing in the lower unit besides the seals looks to be in excellent condition.

 

[Blackhawkdriver]

I've removed the bypass covers. Their was no evidence of carbon build up. I do however to tear down the engine once I figure out if my lower unit only requires a seal kit to re assembly. Everything thing in the lower unit besides the seals looks to be in excellent condition.

 

[Blackhawkdriver]

Well I may have determined where all the metal shavings are coming from. Well as least some of it. The two shims on top of lower driveshaft are extremely worn and corrosion. Yet it doesn't explain some of the larger pieces I've found in the housing. With zero evidence of gear, bearing, or housing damage to have caused that much metal.

My plans remain the same. Put it back together. I figure that the only thing needed will be a seal time and new water pump gaskets. The water pump has less than an hour on it.

Then I'm planning to tearing down the motor and determining what is wrong with it. After further investigating the motor. The number 4 spark plug looks as if the piston had hit it. However there is no damage to the top of the piston that I can tell using a bore scope video camera and looking into the bypass covers.

 

[emdsapmgr]

Possible that the top piston ring on #4 failed. Once ring starts to disintegrate, the resulting large ring pcs wind up in the combustion chamber and can get wedged between the piston crown and the top of the head or spark plug. Then the small pcs blow out the exhaust ports. Check down inside the prop exhaust area and see if there are any remnants of the ring still laying there.

 

[emdsapmgr]

Possible that the top piston ring on #4 failed. Once ring starts to disintegrate, the resulting large ring pcs wind up in the combustion chamber and can get wedged between the piston crown and the top of the head or spark plug. Then the small pcs blow out the exhaust ports. Check down inside the prop exhaust area and see if there are any remnants of the ring still laying there. Also, when you have the head off, check the placement of the rubber water diverter by #4 cyl.

 

[Blackhawkdriver]

Emfsapmgr, Thank you for the input it has been a great deal of help. I will defentantly let you know. It will be sometime before I get it tore down. Hoping to order the lower unit seal kit to put back together this coming payday. One thing at at time one step at time a day at a time.