Replacing melted piston 91 Evinrude 150 XP

[TheStinkMan]

I recently purchased a 92 Nitro 180 that has a 1991 Evinrude 150 XP. Performed a compression check and the bottom left cylinder was at 70 (Bottom Left looking from the back of the boat to the front) all others were 95-100. I pulled the head on that side and the piston head is melted. The head and cylinder walls look good. I see no other damage. Wondering if I have to pull the entire block to replace the piston or can I pull the carbs and reed box to R&R the piston with a new one? Engine Model Number: TE150SLEIE

[bktheking]

I'm gonna say yes , you need to pull the powerhead off and split the crankcase to get at the connecting rod, head will have to come off.

[TheStinkMan]

Also looking for a used regulator and stator for this motor or an entire motor for parts if the price is right.
Part Numbers:
Regulator: 0395204
Stator: 0584292

[emdsapmgr]

When you have it apart, to replace the one piston-I'd re-ring the other 5 pistons. You should find out the reason for the failure or it will happen again on the new powerhead. Pull the carb apart that feeds that cylinder and check the jets on that side of the carb. May be debris in them causing a lean condition...

[TheStinkMan]

We started the boat before the purchase (water hose hookup while on the trailer). It started, idled and revved fine. Two weeks later got a chance to drop it in the water for a test run and all it would do was putt around. Anything more than Idle under load and it would die. Pulled it back out pulled the cover and that's when I noticed the wires on the regulator were burned/melted. It didn't smell or look like it had just happened. The regulator looks like it actually caught on fire and burned the bottom of the stator. The guy I purchased the boat from said it ran fine last time he had it out but that was over a year ago. I need to replace the regulator and maybe the stator, clean all the carbs and since I have to pull the case to replace the piston I'll probably re-ring all 6 pistons. Should I look for another engine and part this one out or drop another $1,000 plus in and hope for the best?

[wilde1j]

Well, you may have learned something useful here. Running an outboard w/o load on the hose tells you nothing about it's condition, other than it will start and run. No way the motor "ran fine last time he had it out" in the condition you bought it. emdsapmgr has it right ... find the exact cause of the burned piston, or it will surely happen again. If you've never done a major rebuild before, get an OEM shop manual, which will explain exactly what you're in for, then decide whether you want to rebuild or get another motor.

[TheStinkMan]

Thanks for the help. I've got the manual on order as this will be my first outboard rebuild. I rebuilt a few car motors when I was younger but no outboards. Any gotcha's I need to look out for?

[jonesg]

No overhead cams, timing chain/belts or valve trains to deal with.
2 strokes are a lot simpler, you need to find a marine engine machine shop to do the piston/block fitting.
Rebuilders around Boston charge $3K for 6 cylinder, complete rebuild and test run with guarentee, going diy will be a lot cheaper.
If you rebuild it, you'll know exactly what you've got, you aren't going to find a motor that runs like new for that money.

[Dhadley]

Before you tear into it find out what caused the damaged piston. Otherwise you may be in for a repeat performance.

[emdsapmgr]

A factory service manual is almost a requirement on any rebuild. You can contact Ken Cook Co., in Milwaukee for the exact one you need.

[TheStinkMan]

I would think the carb was the problem but won't know till I dig into them.

I've got the factory service manual coming.

My game plan:
a. Replace bad pistion w/new pin
b. Hone all cylinders
c. Replace rings on all pistions
d. Replace Reg/Rect
e. Clean Carbs (Repair if needed)
f. Replace spark plugs
g. Test Stator (Replace if defective)

I'm I missing anything?

Thanks...

[bktheking]

Check your crank and bearing conditions as well as measurements. You will need a full gasket kit as well and while its apart you may as well do the thermostats.

[mitchell6]

how long or how high did you rev up the motor on the hose? that could have got it hot and caused the problem, did that myself to a 135hp Johnson a long time ago didn't know then that you wasn't suppose to go wide open throdle while on muff's. Learned my lesson the hard way broke a ring and beat up the piston

[emdsapmgr]

When you overhaul the carbs, use an aerosol carb cleaner. Blow out the passages with it and check the spray out of the exit orfice from each passage. Compare the spray from one carb passage with the spray flow from the same passage on the other carbs. It's not unusual for dried fuel to clog or reduce the passage diameter, causing lean running conditions. Pull all the jets and visually inspect them.

[TheStinkMan]

When we ran it on the trailer we didn't rev it that much just a little. No telling what he had done previously showing it to other prospective buyers. I want to thank everyone for their helpfull input. I will update this thread with my results as they progress.

Thanks...
TheStinkMan

[TheStinkMan]

Found 3 small groves in the cylinder. About 1/16 wide each. They are very shallow, maybe 1/200 of an inch (you can feel them and see them but barely). I might be able to hone them out. 1/100 (very slight groves). How far can you hone the cylinder down and still use the a stock piston and rings?

[TheStinkMan]

After reading the forums on the subject. I'm going to drop it off at the machine shop and have them look at it.

I plan on putting new rings all the way around and my thoughts on the cylinder(s) are:
1. If they can hone / bore the grove out of the one cylinder and keep it within speck then I'm good.
2. If all cylinders are within speck except the one with the groves I can have them sleeve the one cylinder to fit a stock piston.
3. If any of the other cylinders are out of speck I will have to have them bore them all and order oversized pistions.

The crank and rod bearings seem a bit expensive. Can I get away with using the old ones? How can I tell if they need to be replaced?
0319244 RING $6.76 x 9
0320499 BEARING RACE, Center main clip and $51.39 x 2
0387041 BEARING Assy, Center main $21.88 x 2
0387787 RETS&NEEDLES AY $54.42 x 6
Subtotal = $533.90

Thanks...

[Faztbullet]

If all cylinders are within speck except the one with the groves I can have them sleeve the one cylinder to fit a stock piston.

Resleeving is more expensive than to have it bored, I would just bore it. You can get a .010-.064 piston for that engine.

0319244 RING $6.76 x 9

Those are crankshaft seal rings and doubt need replacing unless broken..

0320499 BEARING RACE, Center main clip and $51.39 x 2
0387041 BEARING Assy, Center main $21.88 x 2

Are these damaged?

0387787 RETS&NEEDLES AY $54.42 x 6

No wrist pin brearings?

[TheStinkMan]

Can you bore only one cylinder?

The crankshaft seal rings look ok (not broken). I didn't know if these where a standard replace item.

I haven't removed the races off the crank bearings yet. But I don't believe they are bad (I feel no roughness when turning the crank by hand).

I've only removed the one piston rod. The bearings look fine but I really don't know what to look for. I know when a wheel bearing starts feeling rough when you turn the wheel it's time to replace them, but I've cleaned a few of them up and some have looked new but I knew they were bad???

Wrist pin bearings, I missed those in the diagram (They remind me of u-joint bearing needles). I'd like to know if it's standard practice to replace them when you crack the case or do you replace them only if you replace the piston.

Thanks...

[Faztbullet]

Can you bore only one cylinder?

Yep.. The oversize piston is the same weight as a stock so no balance issues

The crankshaft seal rings look ok (not broken). I didn't know if these where a standard replace item.

Only if broken or lip worn into edge of it, they should be flat on both sides...

I've only removed the one piston rod. The bearings look fine but I really don't know what to look for.

Inspect the center main bearings/race for discoloration from lackof lube or heat. Inspect needle and race for pitting ,spalling,chips or water marks..replace if needed. Also inspect the upper and lower bearing on crank.

Wrist pin bearings, I missed those in the diagram (They remind me of u-joint bearing needles). I'd like to know if it's standard practice to replace them when you crack the case or do you replace them only if you replace the piston.

Replace them when you change a piston

[trimmers]

I feel your pain. I got the exact same issue on my no.5 cylinder (175 TLCU). I tore her completely down and prepairing to replace all the rings on the pistons and spot check all the bearings on the crank. Not sure how my issue happened. But feverishly looking. Luckily, no damage whatsoever is found in the cylinder itself, just localized to the top of the piston. I am looking at about 150 to 200 dollars in rings, seals and o-rings but ya know, when she is all done, atleast i know the engine is freshened up and ready for a fun summer of boating. Good luck bro

[TheStinkMan]

Took the power head and pistons to the machine shop. They say the #6 (cylinder with melted piston and small groves) can be cleaned up boring .020. They also mic'd the 5 pistons:
#1 3.492
#2 3.492
#3 3.493
#4 3.493
#5 3.489
#6 Not mic'd, melted piston

He says the pistons show some wear. I'm hoping I can re-use them. What do you think?

Thanks...

[emdsapmgr]

The spec for a new factory 150 piston is: 3.4955-3.4965.
The new factory bore spec is: 3.4995-3.5005
A decision to replace pistons should depend on the stackup of total tolerances. You did not say how dimensionally worn each of the bores is. That needs to be part of the overhaul decison. If the bores are tapered and egg-shaped you may need to bore and go with new pistons anyway. Generally, you can reuse pistons if they clean up well. Reusing worn pistons (with new rings) in worn bores can work, but will reduce the long-term life of the overhaul. You need to compare costs to overhaul with other options.

[TheStinkMan]

The boat is a recently aquired 92 Nitro 180 that has had a rough life. I'm not looking for new just reliable enough to cut across the lake for a couple years without worring to much.

Thanks...

[Faztbullet]

Are those measurements the top or skirt of piston? If they are the skirt spec's pistons have a lot of wear, and the cylinders are most likely worn in the port transfer area. I would just go ahead and bore the rest .020 and have a good engine instead of a ok engine as you may find another hull later and will have a good engine to install on it.