pitted piston (bad) 175hp 89 johnson

[ljrichey]

ok --newby to the thread--but half mech--got the boat & mtr this wknd knew it had a cyl down --head removed on bad side --bottom piston pitted bad ---didn't break any rings that i can observe--port side --I am doing whatever it takes to do it myself but am wondering what caused this to happen --head looks good--- have some what looks like gaulded aluminum on cylinder wall but looks like it may hone out --all other cyls cked at 100 psi on comp ck cold ---think i'm ok there---what happened to destroy the one piston?

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

am wondering if a leaking head gasket or water in cyl could cause this kind of damage to the piston---did not see any evidence on gasket that it could have been water---

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

A common failure mode on these crossflows. You may find carbon around the ringsets or on the piston skirt. The carbon will prevent the cooling fuel/oil from reaching the top piston ring. That ring will run hot, then eventually crack. If you don't see carbon accumulation, then you could have an issue with one of the water diverters which can cause just one cyl to overheat. The pcs of the ring will wind up in the combustion chamber and will beat themselves between the piston top and the head, causing the dents. You'll have to tear the engine down to replace at least one piston and 4 ringsets. Depending on the cylinder walls, you may need to overbore it-let a marine block shop measure the block, then decide what has to be done. Bombardier recommends an annual dose of their Engine Tuner to eliminate carbon accumulation on the pistons.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

thanks captain--- the part i couldn't understand is that the head chamber for that particular cyl had no pitting or damage---all the damage was on the piston & the top ring still looks to be intact--some of it (the top ring) is exposed but not broken--could all the sluffing from the piston have left thru the exhaust port without damaging the head chamber? can the gaulded aluminum be honed out without taking to much of the cyl wall with it? am going to try to keep this to a 1 hole repair--hopefully --- you mentioned water divertors --where & what are they?--

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

It is always possible that a prior owner had a ring failure, then replaced the ring and the head. That would be unusual-when the ring busts up, it usually takes the ring groove with it-requiring a new piston. It is possible the head was replaced. Regarding the piston aluminum which has laminated itself to the cast iron liner. It can be dissolved with acid. The acid will dissolve the aluminum and not have an effect on the cast iron. You might even be able to acceptably rehone the bore afterwards. The water diverters are rubber pcs which insert into the block, 3 per side. You will see the ends of them when you remove the head. They look like 3/8" hose, but are a specific length and diameter for the application. The factory manual specifies their installation-it is not unusual for them to move out of position slightly, or collect dirt/salt deposits and restrict down the water passaged around the cylinders in the block. If this happens, one cylinder can overheat even when you have a good impeller, and stats.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

thanks again---the acid --would that be muratic or some other acid? Dont think this is really going to be as bad as i thought---1st time for an outboard tear down--always been a little scared to do much of anything to my boat motors----this one wasn't running when i got it---may not run when i'm done---but i am learning a lot---whats the reliability of the motor in question--175 johnson gt--just wondering? the diverters are they cleaned in place or are new ones required?

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

You might try muratic acid. Those rubber diverters (6 of them) are part number 322411-actually called a deflector. Tthey are only about $3 each, so just get some new ones from the dealer. Good to replace on any overhaul. Those 175's are strong engines-they are detuned 235's from a few years prior. They actually put out right at 190 hp at the crank, so they are underrated at 175. Lots of torque and they have high porting, so they will rev higher than the rev limiter. Those old crossflows had many followers years ago and they ran well. It's good to run a can of Engine Tuner through them each year to keep them clear of carbon build-up. If you are going to do the work yourself, get an original factory service manual from Ken Cook Co., in Milwaukee-you will need it when you get into the engine.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

you're right captain----already blew 43 on a generic manual---could have used it on the parts i'm goina have to buy---bet i'm not the first to do that--really specs & torque values is my main concerns for going together---thanks

 

[dazk14]

Re: pitted piston (bad) 175hp 89 johnson

As EMD said, Muriatic acid will dissolve transferred aluminum. Pool supply or Home Depot has it, but expect a gallon.

Others may know where smaller containers can be found.

Be VERY careful with the stuff. The fumes that are released when dissolving aluminum are deadly, not to mention getting acid on your body.

Be careful in the port areas to prevent it from seeping into the aluminum ports.

Have actually wiped down cylinders and revealed cross hatch although it's far more likely on Nickel plated bores.

If it's been awhile on the water pump a kit makes sense. If you decide to cut that corner, the driveshaft seal should be replaced with an impeller.

Good luck.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

thanks dazk---had planned on a pump impeller & anything else in lower unit visual problems---how tough and any special tools required for prop shaft seal?---may try that---had a little water in the lower unit---

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

The propshaft has two seals, they are back to back. One holds the gear oil in, the other holds the water out. Anyway, to keep from damaging them during installation, Bombardier makes special tools to drive the seals in. Keep in mind that water can also enter the gearcase oil reservoir from the shift rod, the oring around the carrier and the upper drive shaft seal. If you are going to the trouble to replace the propshaft seals, why not reseal the whole thing?

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

thanks for reply---don't know if i'll go there until i get the piston done but am a little concerned about the pressure it takes to turn shaft & lower unit by hand ---could be normal--just don't know---i really can'tt feel any shaft play or see anything abnormal after dropping unit

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

Make sure you have good seals/gaskets for the two lower unit screws. Vent and fill screws. Those can also be a problem..

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

OK---lower unit done--looked good---power block done ---think i'm ok there --wont know till i try a crank ---am going to disconnect vr2 and go mix--when it crank time wish me luck--- this is a 500 $ slot machine pull ---don't do that often but i'll do it one time for the fishin--

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

ok---cranked the engine--couple of concerns---temp on middle cyl starboard side running about 10 dg warmer than top & bottom cyls--in the 159 range --muffs---tell tale has medium stream compared to my 140 evin --new impeller--& diverters--checked thermos--no water flow from upper two outlets--when should water exit these outlets? am wondering if water press is up to par from impeller --tell tale hose route up &down cyl head stb side---when thermos open should water exit two upper outlets? good water exit from prop exhaust--port side cyls cooler than stb cyls by 4 or 5 dg--would like to back it down a ramp and run but not one within an hr drive--thinking about dropping lower unit again but dont enjoy shifter bolt whatsoever--has to be some special tool for v6s---any hints or info would help

 

[emdsapmgr]

Re: pitted piston (bad) 175hp 89 johnson

Not sure just what you are referring to as the two upper outlets. Perhaps you are referring to the two exhaust relief ports on the top of the midsection, just under the back lower cowling. Those ports improve idling characterisics when the lower unit is buried underwater. You won't see much water coming out of those ports. The flatback V6 engines do flow water out of those ports, but the bubble back engines (like yours) must dump the water directly down the exhaust leg. The telltale hose should be routed to the top of the block before it goes down and exits the nozzle. That way the block fills with water before it runs out the nozzle. Unless you just changed the impeller, you should always put a new impeller in the lower unit when a new powerhead is installed. Too much invested to take a chance on an old impeller. Same goes for the thermostats. Your engine should idle between 143 and 155 when sitting in the water. It will run cooler when you are on plane and the pressure relief valves open. If you have a pressure gauge hooked in place of the telltale, a new impeller should pump 7-8 lbs at idle.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

thanks captain for the info--yes thats what i was referring towere the exhaust relief ports --gives me a little piece of mind there--i did put a new impeller in but it just didnt seem to have as much telltale press as my 78 140 even--will ck press with gauge --does water press on muffs have an effect on impeller press? want to thank you again for all the help---i'v really learned a lot on this forum from you guys and have a lot more confidence working on an outboard--i'm sure down the road there will be more ?????????

 

[James R]

Re: pitted piston (bad) 175hp 89 johnson

Looks like you have done a good job.
Water flow and pressure cannot be assessed using muffs. The system is influenced by the faucet pressure. The only way to check is to get the lower into a tank or pond and be sure that the pump is set below the surface of the water.

 

[ljrichey]

Re: pitted piston (bad) 175hp 89 johnson

my mind is a lot more at ease--had a guy bring in a stock tank to run it in and the engine ran at about 120 119 on all cyls---really glad to see that and puts my mind at ease---had a little trouble gettin it cranked up runnin double oil but a little carb cleaner on the plugs did the trick there---might have chocked it to much too---lot of difference running on muffs vs tank run--volume of water may come into play there--once again i want to thank all you guys for the onfo & tips on this thread---look at it all the time to see what other probs others have---makes me feel fortunate sometimes---bout time to make a pull to the lake