1993 200. Piston toast. Thoughts on repair options.

[beantown]

Just bought a 1993 Grady White 25 Sailfish.
Has twin Yamaha 200 2Strokes Model 200TXRR / 6G6 UL 764378

I knew the motors were old, but the powerheads have 600 hours on them.

Anyway, ran a compression test and 11 of 12 cylinders all came in at 120psi.
Unfortunately 1 came back with 0psi.

I pulled the head to see what the deal was and the piston is toast.
Piston:

Head:

So, what would you do here? New powerhead? Repair piston?
Repowering all together is way too expensive for me right now.

Any tips or thoughts would be great. Thanks

[panasonic]

Just bought a 1993 Grady White 25 Sailfish.
Has twin Yamaha 200 2Strokes Model 200TXRR / 6G6 UL 764378

I knew the motors were old, but the powerheads have 600 hours on them.

Anyway, ran a compression test and 11 of 12 cylinders all came in at 120psi.
Unfortunately 1 came back with 0psi.

I pulled the head to see what the deal was and the piston is toast.
Piston:

Head:

So, what would you do here? New powerhead? Repair piston?
Repowering all together is way too expensive for me right now.

Any tips or thoughts would be great. Thanks

More disassembly required...

What caused this destruction and what else is damaged?

These would be my questions to myself..

[amahaork]

Easy to rebore and rebuild one, but learn to helicoil after broken bolts drilled out. I had 12 broken bolts and rebore 2 cylinders.

[99yam40]

probably running lean on that cylinder and overheated piston and lost apiece of ring that flopped around in there beating up things.

If repairing yourself it would be less cost, but paying someone it will be expensive.
as old as it is there maybe lots of stuck bolts.

if it comes apart easy it should not be too bad to repair.
tear it apart and then decide

[beantown]

After pulling the heads, I have been surprised how easy the bolts have been to remove. I'm sure the rest will be welded in since I just said that.

Maybe I should get a .030 over rebuild kit on the way.
I could then remove the powerhead, strip it and get it over to machine shop.
Have them do the cylinders .030 over, then I'll reassemble and install.

Rebuild kits are $1500 or so. Machine shop should be $500 or less.

Gotta look to see how much a replacement powerhead is, maybe that makes more sense.

I'll have a pro go over the fuel/oil delivery once back together to hopefully avoid a repeat. Not sure how it happened since I just got the boat.

[99yam40]

I would pull it apart before ordering anything.

just to make sure what all is needed and how well it comes apart.
no need to have parts sitting there if you find out you do not want to do it anymore

[panasonic]

That may be the only cylinder damaged. You have to take it right down to repair the bad hole. If all the other cylinders are still in spec (you have good compression on the rest) and no crank damage. Have that cylinder only bored and install oversized piston and rings...would be much cheaper that way..

Take it apart and see what you got to work with..

[amahaork]

Need to disassemble to the bare block. Shavings from cylinder bore will be everywhere. Need to wash block clean.
If other cylinders and pistons not damaged, new piston rings required - that open for debate.

[beantown]

I took the powerhead off and with the exception of that piston/cylinder, the rest looks really good to me. Didn't break a single bolt breaking it down either.
Saltwater boat too.

I suppose I'll have the machine shop decide how much to oversize the cylinder.
.030 over or less would work.
Definitely some aluminum smeared on the cylinder wall.

Gotta gather the parts/gasket list and get them here pronto.
I'm on vacation next week and want to be on the water, not working on the boat all week.

[beantown]

Need to disassemble to the bare block. Shavings from cylinder bore will be everywhere. Need to wash block clean.
If other cylinders and pistons not damaged, new piston rings required - that open for debate.

If the machine shop won't do one cylinder while the other pistons are in, then I will try to hone the aluminum off the walls and put a stock size piston and rings in it......and pray.

Not a great decision, but I will roll the dice to get on the water.

Winter time I am gonna pull both engines and renew them.

Sure would be nice to have two new 4strokes on the stern.

[ausnoelm]

Don't see the sense in boring it with the other Pistons still in, and I doubt any machine shop will do it that way for you. You need to have a good look at the bore, forget the piston, just replace that anyway, but, the bore might be fine with a "clean up" then find why it happened in the first place, or be prepared to do it again real soon.

[beantown]

I was able to clean out the blown piston cylinder with muriatic acid and then did a light hone to give it a final touch.


Gave everything a good cleaning while it was torn apart and reassembled the powerhead.

Two head bolts and one intake bolt needed to be helicoiled since the original threads stripped out while tightening them to torque spec.

Assembled everything and dunked the lower unit into a 50 gallon barrel of water to start and test.

She started right up and sounded better than ever.
Rev'd it up to 2500 or so and then just let her idle for 10 minutes or so.
A running hose was left in the barrel to replenish spill over.

After 10 minutes or so a quick alarm and motor shutdown.
Argh. No idea what the alarm was, figured it was an overheat, but nothing was apparent on the gauges.

Haven't been able to start it back up since.
Strange since it sounded so good.

Ran a compression check and all 6 cylinders are about 120psi.
Spark test shows spark.
Spark plugs get wet after reattempt to start.
Changed water separator filter and cleaned out engine mounted fuel filter.
Still nothing. Just cranks like there is no fuel or spark.

This motor is 1 of 2. The port motor starts right up and runs fine.

Maybe timing? Been banging my head on this for two days now.

[beantown]

Just noticed something that might not be good.

I was following the service manual to make sure the timing pointer was in the proper place before moving on to adjust carb/magneto link prior to timing with light.

The flywheel markings indicating where each piston TDC is as it passes the timing mark is 180degrees off.

Two questions arise:
1.How the heck did I manage that?
2.How did it run so well at first start post work done?

[beantown]

Well this explains it....

Sheared woodruff key.
I guess I should remember to torque the flywheel nut next time.

[amahaork]

Use magnet to collect metal pieces digging key out of crank.
Follow break in procedure and mix.