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Oh just pullin a 15 month old sbt engine

spatty99

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I had about 300 flawless hours on an MR1 SBT engine (and then sold the boat). It even had better annual oil analysis results than the factory engine.
 

Ronnie

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I had about 300 flawless hours on an MR1 SBT engine (and then sold the boat). It even had better annual oil analysis results than the factory engine.
Just curious, which engine option and warranty package did you buy?
 

Jaycav

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Just curious, which engine option and warranty package did you buy?
The one that failed was SBT standard. This time around I order the premium
 

Jaycav

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Took oil apart and cleaned/rebuild her. The screen did a good job of catching everything D346A7F7-8EB9-4CB3-808A-65B58C3ED306.jpeg
 

Jaycav

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Back together Like brand new D158EA5C-CE72-406E-842C-1B201F719C33.jpeg
 

Jaycav

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Jaycav

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My new motor is due for delivery Monday so I completely pulled old engine apart. I do believe the problem was the timing chain guide. The part of the guide that broke is where the tensioner actually pushes on the guide. I think it was just a faulty part. The pieces of the guide blocked the oil passage just enough to starve the last valve which ended up sticking. Piston hits valve, piston explodes etc. 79A5D94E-05B8-43B6-A22B-A80471449A5A.jpeg
 

spatty99

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I had the premium/Yamaha version, with the 2 year warranty.
 

Jaycav

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Jaycav

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I had the premium/Yamaha version, with the 2 year warranty.
That’s what I got this time. Let’s hope last longer than the last one
 

WREKS

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@Jaycav Thanks for the continuous updates. I have some questions. I cannot see the smashed piston and broken lifter scenario without a broken timing chain. Is it possible that a plastic guide piece or whatever caused the guide to shred got between the cam and the lifter? Did the guide piece delaminate? What does the timing chain tensioner look like? Therefore, I do not see how you are responsible for this. Am I reasoning correctly?

Edit Second scenario: Delaminated chain guide allowed for loose chain leading to chain jump.
 
Last edited:

Jaycav

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@Jaycav Thanks for the continuous updates. I have some questions. I cannot see the smashed piston and broken lifter scenario without a broken timing chain. Is it possible that a plastic guide piece or whatever caused the guide to shred got between the cam and the lifter? Did the guide piece delaminate? What does the timing chain tensioner look like? Therefore, I do not see how you are responsible for this. Am I reasoning correctly?

Edit Second scenario: Delaminated chain guide allowed for loose chain leading to chain jump.
The timing chain was not broke. The tensioner looked fine and was still Functionable. The guide did look like it delaminated. The chain seemed tight but your theory of chain jump which would cause a valve to hit a piston is a possibility and it makes sense to me.
 

WREKS

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The timing chain was not broke. The tensioner looked fine and was still Functionable. The guide did look like it delaminated. The chain seemed tight but your theory of chain jump which would cause a valve to hit a piston is a possibility and it makes sense to me.
When I say delaminated I mean-the new guide looks like it has a thick curved wedge fused/plastic welded to it. That is the part that is missing from the failed guide. The chain tensioner pushes against that wedge. That should not have fallen apart. The slack created when that wedge came off the guide, could have allowed the chain to jump.
 
Last edited:

Jaycav

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When I say delaminated I mean-the new guide looks like it has a thick curved wedge fused/plastic welded to it. That is the part that is missing from the failed guide. The chain tensioner pushes against that wedge. That should not have fallen apart. The slack created when that wedge came off the guide, could have allowed the chain to jump.
I agree
 

Jaycav

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Boo yah B2BE72CB-2683-4F3E-B1F9-56BBD0539106.jpeg
 

Jaycav

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She’s in 568F42C8-0E4D-4A32-8B6E-43C7BD8D5286.jpeg
 

anmut

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Nicely done! Let us know your on-water results!
 

Ronnie

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@Jaycav , do you did this kind of work for a living or hobby? I’d bet the former because you seem to have all the skills and tools needed.

I hope the new engine has no gremlins and lasts as long as you own the boat.
 
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