Weird Engine Issue

ESPNSkierESPNSkier Posts: 113 Baller
I have a 1993 MasterCraft ProStar 205 with an Indmar 351 with about 1,100 hours on it and it has been running great. However, last week as I was coming into the course the engine blew out the spark plug in cylinder #2. As it turns out I have a cracked head and I'm replacing both heads. The weirdness happened when I pulled the heads and discovered that the piston in Cylinder #6 (2nd cylinder on the port bank) is rotated upside down. If you look closely at the 2nd image you can see the word "Up" and an arrow....pointing down! I have owned the boat for more than 19 years and the engine has never been apart so I assume that it was assembled with one piston reversed at the factory. Should I be concerned or just put the new heads on and hope for another 1,100 hours?

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Comments

  • oldjeepoldjeep Posts: 2,442 Mega Baller
    edited June 5
    If the valves haven't contacted the piston in the last 1100 hours it should be just fine as long as the new heads don't require more valve clearance than the old ones. It is interesting though ;)
    Chuck P
    Not a mechanic but I play one at home
  • ESPNSkierESPNSkier Posts: 113 Baller
    Thanks @oldjeep, that's what I'm hoping!
  • bigskieridahobigskieridaho Posts: 489 Solid Baller
    I would change it around if you are going to put new heads on it. The clearances won't be the same, and it wasn't right in the first place. I know it means pull the engine, but will be a piece of mind in the long run. You can leave it, but I wouldn't. Easy to pull....Git er dun!
  • gregygregy Posts: 2,256 Mega Baller
    nice quality control there. Some Ford tech was asleep that day.
  • 303Skier303Skier Posts: 445 Solid Baller
    So weird! Was installed that way or the rod broke. I'd install new heads and then hand rotate crank and feel for any binding. remove all spark plugs.
    Jarrus Steele - Orlando, Florida
  • cruznskicruznski Posts: 27 Baller
    Since you have it all down to this level I'd pull it and rotate that piston- it's just not right. Kind of a testament to the tractor nature of those motors, but still you aren't that far away from correcting what was a factory major faux pas.
    adkh2oskier
  • DanEDanE Posts: 762 Crazy Baller
    Turn it around, there is more to pistons than meet the eye. For instance bore for the piston bolt could be assymetrically positioned. The recesses are not for valve clearance they are combustion chambers. probably has a slight efffect on intake and exhaust breathing of that cylinder as well as mixture when the chamber is assymetrical like that ( looks like it ran a little richer than the others)
    GWaterski
  • DmaxJC_skiDmaxJC_ski Posts: 329 Baller
    19 years and over 1000 hours..... if you are using a stock replacement head, I would run it. And if your concerned about clearance run a thicker head gasket.
    gregyoldjeepBill22303Skier
  • Stevie BoyStevie Boy Posts: 1,445 ★★★Triple Panda Award Recipient ★★★
    Aircraft Engineer, I would not be able to live with myself, if I ignored it, think about it, you go to all the trouble to, put nice new heads on it, and the bottom end gives out, or the piston makes contact, no good just turning the engine over, to see if it makes contact, when the engine is running there is certain amount of throw, with some wear as well, that piston could travel quite a bit more and make contact.

    "In my mind there is more potential to be released.”

  • GloersenGloersen Posts: 621 Crazy Baller
    edited June 5
    The time and effort to rotate that piston will not likely provide any gains considering the history; it'll just reduce water time.

    diligently prep the block's mating surface for the new head gaskets, use new head bolts, replace with new heads and... go ski!

    stå løpet ut
  • Stevie BoyStevie Boy Posts: 1,445 ★★★Triple Panda Award Recipient ★★★
    Out of interest, 1100 hrs, how many hours left before a Engine refresh is likely to be required ?

    "In my mind there is more potential to be released.”

  • ESPNSkierESPNSkier Posts: 113 Baller
    Thanks all, great advice here! Given the time of year, I agree with @oldjeep and @Gloersen and plan to put on the new heads and hope for the best. These are GT40 heads and the Machine Shop is telling me that these heads have a crazy amount of clearance. If it was December I would most likely pull the engine and do a total refresh. As @oldjeep said, once I pull the pan I would pretty much have to do a total refresh....maybe next winter. @Mark_Matis, I believe you hit the nail on the head as there was significant blockage in the cooling passages which I'm sure contributed to the cracked head and is probably related to low water levels this spring.
  • kdeupserkdeupser Posts: 51 Baller
    Don't tear that motor down just to flip the piston. It will probably destroy itself if you flip it since it's worn in upside down. If you have any concern about piston to valve clearance just clay one piston and then mic the clay.

    Those are very low compression pistons anyways so you should be fine. I've seen the 351 windsors go for 2 to 3 thousand hours.

    I would probably go with a head from "Trickflow" if I were you. Then when you see the need to freshen up the bottom end I would go with at least flat top pistons with a mild cam. That engine is easy to make respectable power out of so good luck.
  • spicolispicoli Posts: 85 Baller
    I believe the piston dome is designed like that for a reason and really should be installed right way will it work, well it has been but that don't make it right.but I'm with old jeep if u pull it might as well put new bearings and ring it why not all that money brand new heads take your time do it rings and bearings are cheap compared to heads if you jump on it it won't take long turn few bolts o yea don't forget new oil pump and water pump
  • spicolispicoli Posts: 85 Baller
    O yea and what if the connecting rod is backwards then the oil holes could be off some
  • MitzysmanMitzysman Posts: 149 Baller
    i personally would leave it - it has worn in the way it is. Cleaning the crud from the cooling passages is more important - i have 2 friends with same vintage MC engines that lost a cylinder due to the crud build up.
  • MISkierMISkier Posts: 1,745 Mega Baller
    I have heard of overheating in a specific cylinder and melted piston due to poor cooling created by silt blockage in the engine. Apparently, it eventually hardens to concrete inside the block.
    The worst slalom equipment I own is between my ears.
  • ESPNSkierESPNSkier Posts: 113 Baller
    Thanks @Mark_Matis, I may need to do some plumbing work this winter.
  • Fast351Fast351 Posts: 196 Baller
    The other thing about flipping that piston is that the rods are NOT symmetrical. The chamfer on the crank side of the rod has a bigger radius than the side that contact the adjacent rod. That means you have to flip the rod in the piston. This is not something you can do by hand without special tools since the piston pin is pressed into the rod. Machine shops use a special torch jig to heat up the small end of the rod so the pin can be pushed out.

    Personally I'd leave it. Who knows what kind of strange wear patterns you could develop by putting a piston in that's used.
    Mike van Meeteren
  • Fast351Fast351 Posts: 196 Baller
    @Stevie Boy It really depends on how diligent the owner is with maintenance. Generally speaking 2000 hours should be expected out of a marine V8 that has had reasonable maintenance. 3000 hours isn't out of the question but I would consider that near worn out.

    @ESPNSkier put the heads on and run it. The amount of labor saved in doing a complete teardown right now isn't that great. You could always yank it this winter if it bothers you.
    Mike van Meeteren
  • DWDW Posts: 1,480 Crazy Baller
    @ESPNSkier : as an FYI, the piston pin is offset in the piston. The purpose is to reduce piston slap specifically on cold start up, which you may hear from your #6 configuration. As noted, the combustion characteristics will not be ideal or same as others along with the potential of valve to head contact being much greater with mismatched piston orientation. I would do a clearance check (using clay) for 2 cylinders to compare valve to piston clearance on standard v. offending one. All the comments on tearing the bottom end apart are valid.
  • ESPNSkierESPNSkier Posts: 113 Baller
    Good point @Mark_Matis, I did not think about that! Don't tell anyone but I haven't skied a tournament since the mid 80s. The funny/sad thing is that we have had one of the windiest springs that I can remember but it has been glass calm every day since the spark plug blew out....and it's driving me nuts!!!
  • ESPNSkierESPNSkier Posts: 113 Baller

    10 days and $1,300 in parts later she is running again! I did not get to do a test run due to rain late yesterday but....no weird noises, no visible leaks and no sign of water in the oil after running in the boat house for about 30 minutes....hopefully, all is good! Had a scare when one of the new head bolts rung off while doing a final torque to 110 foot pounds. Replaced it with one of the old bolts and hope all is well.
    oldjeep
  • DWDW Posts: 1,480 Crazy Baller
    @ESPNSkier : I assume you mean rounded off the bolt head, not snapped one of the cylinder head bolts? One can be somewhat leery depending on where sourced of new hardware quality, many reports of defective hardware from off shore suppliers. Not parts you want on that airplane you are about to lift off terra firma on...
    oldjeep
  • oldjeepoldjeep Posts: 2,442 Mega Baller
    x2 I'd be a bit concerned with a head bolt that you could snap off with only 110 ft/lbs
    Chuck P
    Not a mechanic but I play one at home
  • ESPNSkierESPNSkier Posts: 113 Baller
    @DW, no, I mean''t total bolt failure as one of the new 1/2" bolts snapped in the threads above the block. Fortunately it came out and I did not have to drill and tap it. The others torqued OK.
  • oldjeepoldjeep Posts: 2,442 Mega Baller
    Keep an eye on them and consider re-torque after a few heat/cool cycles to make sure.
    Chuck P
    Not a mechanic but I play one at home
  • ESPNSkierESPNSkier Posts: 113 Baller
    Thanks @oldjeep, that's my plan!
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