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  1. #1
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    SBT Engine Failure, Buyer BEWARE

    I had a recent Tigershark engine failure. This is a long post, but maybe some of you can benefit from my recent experience.

    New to PWCs but not to engines. I have over 50 years of engine building and troubleshooting experience. In the 70s I was a certified OMC, Johnson/Evinrude, mechanic. I also taught technical education for 35 years. Everything from lawnmowers, motorcycles, outboards, automotive, marine gas and diesel, as well as heavy equipment diesel engines. There is a reason for every failure. The reason must be investigated and resolved or you are doomed to experience it again.

    I previously sent SBT all of this information in private so they could respond, and perhaps learn from their error. The response was not at all what I had expected. They chose to respond telling me about how great their quality control is, not even addressing the fact they used an incorrect part which caused the failure. I do wonder how many others have failed in this same manner.

    History;
    I purchased 2, non running, 1998 TS770L boats a while ago. One had an engine seized from being run with no oil. An assembled engine with a warranty was only about $20 more than the required parts, so I purchased a TigerShark 770 rebuilt engine from SBT in June 2014. Did not install it May 2015. It ran fine. I burned about 5 gallons of fuel in 2015. In 2016 it burned about 6 gallons before it broke. Not even a full tank of fuel has been run through it. (I always drain the tank when winterizing then put in new fuel the next season) The graphite coating on the pistons is not even worn off yet.

    The Failure;
    While cruising with just enough throttle to stay on plane, the boat suddenly shuddered and the engine stalled. I thought maybe I had sucked up a stick or something. The engine would not turn over when I first tried to restart. After a few attempts and a couple of prayers, I was able to restart and to ride on. Heading back to the dock, the engine was running fine, until it shuttered again, then ran on only one cylinder. There was no one else around so I was not able to get a tow. I headed to shore, hugging the shoreline back to the dock to limit the distance I would have to swim in the event it stopped completely.

    I began to investigate the engine, now over a year out of warranty, back in my shop. I discovered a damaged MAG side spark plug was the reason for it running on only one cylinder. Removing the head revealed significant damage to the MAG side piston, head and plug. Damage of similar pattern but much less severe in the PTO side cylinder.

    Photo1.jpg
    Close inspection of the damage suggests that something odd shaped was ingested. Other dents suggest something round and hard, like a bearing needle was ingested. I was however puzzled how this would damage both cylinders.

    Failure Analysis;
    I removed and fully disassembled the engine. What I have discovered should be of great concern to anyone who has or is considering the purchase of an SBT engine.

    The new reeds which were installed were still in perfect condition. They would have shown some kind of damage if something outside the engine had been sucked through them.

    The first troubling observation is the huge amount of sealant between the crankcase halves. The Tigershark service manual states, Apply a LIGHT COAT of Artic-Cat High-Temp Sealant to the bottom crankcase half. As the halves are assembled and torqued properly almost all of this LIGHT COAT should be squished out, remaining in minute imperfections, creating a tight, dimensionally accurate crankcase. This is true of all split case engines. The sealant remaining in the seam on this engine is totally unacceptable. One has to question how could this much possibly REMAIN between properly torqued case halves. The sealant at the center bearing is 0.012 thick. Tapering to 0.007 at the PTO end and to 0.006 at the MAG end.

    photo2.jpg

    Examining the crankshaft as it still lay in the top half of the crankcase revealed the cause of the cylinder/piston/head damage. There are 4 bearings, each has a small steel pin on the outside of the bearing. These pins keep the steel bearing race from rotating in the aluminum case. TWO of these pins are missing. One of the two remaining pins was not straight as it was almost out of the hole.

    photo3.jpg

    Further inspection shows damage to the crankcase where these pins fell out and were dragged between crankcase and the crankshaft, gouging aluminum from the case.

    This explains both kinds of piston/head damage. The pins caused the perfectly round dents. The aluminum chunks gouged from the crankcase explains the randomly shaped damage. I have to assume the PTO pin was the first to come out. The crankcase damage is not catastrophic, but there is a deep gouge in the aluminum. This also explains why the engine was reluctant to turn over when I first tired to restart. There is much less piston damage. It appears this pin stalled the engine when the crank caught it. On restart, the pin went though the cylinder quickly and did not damage the spark plug. The MAG side pin came out next. Running at higher speed it went quickly through the crankcase, but stayed in the cylinder longer, damaging the plug.

    photo4.jpg

    Why did the engine fail? evolved into two specific questions... 1) Why was the sealant so thick? And, 2) Why did the pins come out?

    This is what I have discovered:

    1) The center bearing on the PTO side is the thrust bearing for this engine. A groove in the bearing matches a groove in the crankcase. The Service Manual states; Install the C-ring into the upper crankcase half. The bearing on the engine SBT built has a full ring on this bearing. This might have been an acceptable change, perhaps even an improvement over the C-ring. HOWEVER, the ring they installed stands from 0.130 to 0.137 above the bearing. It is TIGHT in the groove with no room to compress as the case is assembled. The groove in the case it is intended to fit into is only 0.125 to 0.130 deep. This is why the sealant was so thick between the case halves. The ring prevents the halves from pulling tightly together. Torquing the bolts down distorted the case, ruining the integrity of the crankcase/crank/bearing assembly.

    photo5.jpg

    2) The excessive gap between the crankcase halves prevented the bearings from being held securely as they need to be in order to remain stable under load. The pins were not squished into the little pockets left for them by the engines original manufacturer. The flexing and vibrations of the crankshaft due to the bearings being loose in the case, caused the pins to work their way out of the bearings, and to damage the pistons, head and cylinders.

    Has anyone else had issues with SBTs high quality remanufactured engines?

    Buyer Beware,

    John
    2, 1998 TS 770 L, restored and running great. (Except for the one with engine that SBT put the WRONG crankshaft bearing into and is now sitting as I collect repair parts)

  2. #2
    Top Dog sea-one's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    ...."new to PWC"
    2004 Rxp Stock Motor with other light mods
    1996 Xp Resurrected july 2014/SOLD 2016
    1991 Kawi 750cc Big pin Twin Carb Sport Cruiser Custom (Resurrected Feb 2015 completed June 2015)
    2000 XP Saved Spring 2016- Resurrected July 2016 as new
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    CANDoo Pro system

  3. #3
    PWCToday.com Is My Home Away From Home kcr357's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    Quote Originally Posted by sea-one View Post
    ...."new to PWC"
    Case closed, that's obviously why the bearing failed
    How many gerbils could a gerbil jammer jam if a gerbil jammer could jam gerbils?


    "You build cheater motor's & still get smoked !!!!"
    "Its not your fault. You just don't understand what you're talking about. "

  4. #4
    PWCToday.com Is My Home Away From Home jetskijockey's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    Common sense would have been to install it and run it instead of waiting a year later... lol


    Sent from my iPhone using Tapatalk

  5. #5
    Frequent Poster Aust the Boss's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    I run a Sbt engine in my Polaris 1200 and it runs great and I have put over 100 hours on it in the last two years. I buy a ton of parts from Sbt and I have never had a problem with them or there parts.

  6. #6
    PWCToday.com Is My Home Away From Home Bruce in SB's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    Great anaylsis of what happened... Makes me wonder how many "engine builders" ... set up in their garages ... would have found a problem like this.
    In SBT's behalf... they did have a 1 year warranty which is more than reasonable considering the abuse some people could do in a year.
    "Thanks" to Chris Newmiller @ Newmiller Machine

  7. #7
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    Re: SBT Engine Failure, Buyer BEWARE

    I have admitted it the engine was out of warranty. I know that is my fault. I did get the engine together and ran it a while before the warranty ran out. I did not have time complete the break-in the first year. Again, my fault. It ran good, I incorrectly assumed that the engine would be assembled with the correct parts so it would be OK.

    That being said, me keeping the engine in the box for 9 months, did in not make the incorrect ring to cause this damage.

    The point I was making was, if you buy one, run it hard while still under warranty.

    John
    2, 1998 TS 770 L, restored and running great. (Except for the one with engine that SBT put the WRONG crankshaft bearing into and is now sitting as I collect repair parts)

  8. #8
    PWCToday.com Is My Home Away From Home Bruce in SB's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    Exactly

    The point I was making was, if you buy one, run it hard while still under warranty.

    John[/QUOTE]
    "Thanks" to Chris Newmiller @ Newmiller Machine

  9. #9
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    Does not appear to be the typical warranty or customer abuse issue this time? Assuming the op description to be accurate, I would assume that SBT was already aware of the problem and would offer assistance under a recall or extended warranty program or similar?? Personally, I would be interested to hear more from SBT on this one...
    Last edited by mcn6; 11-07-2016 at 12:23 PM.



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  10. #10
    PWCToday.com Is My Home Away From Home wmazz's Avatar
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    Re: SBT Engine Failure, Buyer BEWARE

    1 year warranties have been an issue within the watercraft industry for as long
    as I can remember. When you are a low buck local shop it is more common to make
    it the customers problem. But at larger business like when I worked at PJS, I had more
    lee-way to work with the customer. IMO, how a company deals with possible mistakes
    is representative of how the companies owner feels about customer service.

    I have seen the negative point of view several times over my career, where the owner
    looks at their customers as moochers that want to take money out of their pocket. Ed
    Miller was different. I proposed a plan to try to make more money in the PJS service
    department, and his attitude was to take care of the customer first. After PJS closed
    I met someone that had never done business with PJS, and he told me that we had a
    reputation for taking care of our customers.

    About a month ago I commented on this thread 1998 Challenger 1800 - Engine blown
    and I was against using an SBT rebuilt engine for some of the reasons below. Look at
    your engine, they probably don't rebuild many Tigersharks so they need to make due
    with beat-up and questionable engine parts. They remachined the head, lowered the
    compression and increased the possibility of detonation. They used questionable a
    crankcase set. Using the same idea of a limited supply of Tigershark parts, the
    crank rebuilder most likely substituted a Kawasaki main bearing in place of a
    Tigershark Main Bearing
    because he had too.

    On the PJS engine assembly line we used the black 3bond 1107b crankcase sealer.
    Kawasaki, Honda, and Suzuki have all used 1107b on watercraft and motorcycles. So
    if the engine sealer is the wrong color from what SBT normally uses, it is possible that
    a technician had to throw that engine together, and used some of his own sealer to
    fill an order.

    1107b (before the Suzuki number change) has been my goto sealer for years.

    Quote Originally Posted by hemmjo View Post
    A re-machined head to reduce compression!

    This head is an example of what I dislike the most about SBT rebuilt engines. They re-machine
    the stock heads to lower compression as if that was going to make their engines more reliable.
    The real reason maybe machining the head eliminates dings like what are in your head, and makes
    the head more presentable. But as a rule of thumb, for every .002" you machine away on a squish
    band, you are loosing 1 psi.

    But they are also increasing the squish clearance, and increasing the possibility that detonation
    will occur. Very similar to what happened with JS650 heads from Ocean Pro.

    Quote Originally Posted by hemmjo View Post
    photo2.jpg
    “Why did the engine fail?” evolved into two specific questions... 1) Why was the sealant so thick? And, 2) Why did the pins come out?

    This is what I have discovered:

    1) The center bearing on the PTO side is the thrust bearing for this engine. A groove in the bearing matches a groove in the crankcase. The Service Manual states; “Install the C-ring … into the upper crankcase half”. The bearing on the engine SBT built has a full ring on this bearing. This might have been an acceptable change, perhaps even an improvement over the C-ring. HOWEVER, the ring they installed stands from 0.130” to 0.137” above the bearing. It is TIGHT in the groove with no room to compress as the case is assembled. The groove in the case it is intended to fit into is only 0.125” to 0.130” deep. This is why the sealant was so thick between the case halves. The ring prevents the halves from pulling tightly together. Torquing the bolts down distorted the case, ruining the integrity of the crankcase/crank/bearing assembly.

    photo5.jpg

    2) The excessive gap between the crankcase halves prevented the bearings from being held securely as they need to be in order to remain stable under load. The pins were not “squished” into the little pockets left for them by the engine’s original manufacturer. The flexing and vibrations of the crankshaft due to the bearings being loose in the case, caused the pins to work their way out of the bearings, and to damage the pistons, head and cylinders.
    Those crank cases had a connecting rod fail on the PTO cylinder. When that
    happens the con rod forces the crankcase outwards and that pulls the gasket
    surfaces downwards. Depending on if the technicians tested the crankcase for
    flatness, it is possible the crankcase set should have never been used.

    The center bearing is the fault of the crankshaft rebuilder or purchasing agent
    for SBT. (like I said before, it is likely, a Kawasaki main bearing)

    Despite the problems you have documented so well, you are also at fault, possibly
    because you are a good tech. That engine had an air-leak, and you managed to get
    it to run and idle.

    How bad of an air leak is impossible to say. But that engine should have never
    left SBT with an air-leak. That is something I am surprised they don't test.


    Bill M.
    Last edited by wmazz; 11-07-2016 at 10:00 PM.
    Horsepower == Speed, RPM != Speed



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