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  1. #61
    Join Date
    Sep 2010
    Location
    Freeport, Texas
    Posts
    185

    Default Re: Really bad compression #'s on one of my 225's.

    Quote Originally Posted by bobmech View Post
    Have you checked that the crankshaft end-float is within spec ?
    Just wondering if a failed crankshaft thrust bearing is the cause of your cylinder wall bottom wear e.g. crankshaft dropped down and putting downward pressure on con-rods and pistons.

    Bob
    I checked the end-float several months ago before I began any work on the motors. It made no sense to go forward if the thrust bearings were worn. They're good.

    It turns out, the cyls are very round....all 6 well within spec. Surprisingly little wear?!!

    There is a little pitting of the head, next to the valves on #6, which would indicate some water intrusion. No pitting in the cylinder, which seems strange.....but I'll take it. I don't know how there can be enough water to pit the head, but not the cylinder.

    I will get the heads to the shop next week, and then we're going on vacation. So it will be awhile before I have results. It's possible the cost will go up, depending on if they have to replace valve seats, guides, valves, etc. But still.....it's worth a shot. A new short block is $3200 and way too many hours for me, especially since I don't have a shop to work in.

    Yes, I'm rotating the pistons so that they all get the SF worked in. Interesting, today, 24hrs after the first fill, 3 or 4 of the cylinders were still full of SF. None had seeped by?! Does that mean heavy carbon? I assume that over several days they will all start to seep.

  2. #62
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,706

    Default Re: Really bad compression #'s on one of my 225's.

    Only time will tell, IT might mean rings are really good, Have a nice vaca

  3. #63
    Join Date
    Sep 2010
    Location
    Freeport, Texas
    Posts
    185

    Default Re: Really bad compression #'s on one of my 225's.

    Hey guys.....Still a few days left before vacation. I dropped off the heads today and had a brief conversation with the "cylinder head" guy. I explained that I was chasing a problem with crazy comp numbers. When he heard the part about pressurized air (leakdown) escaping out of adjacent spark plug holes he immediately said, "blown head gasket".

    But why both?

    "Engine might have gotten hot."

    If that's the case, then the entire motor could be damaged?!

    "Maybe, maybe not. You won't know until you bolt the heads back on."

    Anyway, I asked him to be on the lookout for any explanation for the wide range of comp psi that could be related to the heads.

    Don't these motors have a shutdown/idle mode if an overheat situation occurs? If so, how would the motor overheat.....at least at high rpms?

    BTW, after several days of soaking and refilling, the Seafoam has turned the carbon on top of the pistons to gunk that I can easily scrape off with a fingernail. So, I'm sure whatever carbon is down in the ring grooves is gunk as well. Any suggestions on how to remove the carbon on top of the pistons cleanly, without getting it down between the sidewalls of the cylinders and the sides of the pistons? Obviously, there's nothing I can do about the carbon in the rings, except blow it out when I run the motor.

  4. #64
    Join Date
    Aug 2011
    Location
    South Texas
    Posts
    567

    Default Re: Really bad compression #'s on one of my 225's.

    I would wipe off as much as you can with a clean shop towel and carb cleaner. Or use gasoline with a nylon parts brush to clean the tops off. Then spray with carb cleaner. Not saying this is the proper way, just the way I would do it. Your oil is going to be nasty, so make sure you change it.

  5. #65
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    3,731

    Default Re: Really bad compression #'s on one of my 225's.

    Yes, the engine has overheat protection. I do not know the exact temp when it kicks in, but suspect it's around 200 F. Supposedly, when the ECM detects an overheat situation it powers down to 1800 rpm. If after 20 seconds it still detects an overheat situation, it will shut down.

    As for getting the gunk off the cylinder tops - you can purchase a heavily restricted nozzle that will fit on then end of a Shop Vac hose. They usually come in a kit of different fittings and most hardware stores carry them under a name like "micro vacuum kit." For example see:

    http://www.homedepot.com/p/Stinger-1...B&gclsrc=aw.ds
    CHawk 25 DLX

  6. #66
    Join Date
    Jul 2008
    Location
    Tauranga New Zealand
    Posts
    123

    Default Re: Really bad compression #'s on one of my 225's.

    If you had a blown head gasket between cylinders, it would be obvious looking at the head gasket, and the compression figures of the adjacent cylinders would be both equal and low.

    Bob

  7. #67
    Join Date
    Aug 2011
    Location
    South Texas
    Posts
    567

    Default Re: Really bad compression #'s on one of my 225's.

    Did you have the heads milled, maybe they were warped from over heating?

  8. #68
    Join Date
    Sep 2010
    Location
    Freeport, Texas
    Posts
    185

    Default Re: Really bad compression #'s on one of my 225's.

    Interesting update guys......

    We just got back from vacation and I called the machine shop. For the most part.....good news.

    The heads pressure-tested fine, but all valve seats/valve faces showed varying degrees of pitting (#6 was the worst), clearly due to saltwater ingestion. Some erosion of aluminum around some of the seats was evident. One exhaust seat on #6 had to be replaced. All seals were replaced. Everything else was reusable. The machinist said there would have been significant compression leakage in the 4 lowest cylinders (#1, 2, 5, and #6), and that compression will come up if the rings are ok. This leakage through the valve seats would explain air coming out adjacent cyclinder spark plug holes during the leakdown test.

    So, no doubt this motor was mounted too low on the previous boat. The mystery is......why one good motor and one bad? The motors are too close in serial numbers to have come off separate boats. My best guess is that these two were part of a trip setup, and the bad motor was in the middle, mounted the lowest.

    The cylinders have been mic-ed as round and no pitting is evident. With the amount of saltwater that was getting into the chambers, I don't understand why the cylinder walls aren't pitted......but I'm not complaining. With a little more luck to go around, the rings will be good enough to get some reasonable compression.

    Now I just have to remember how to put it all back together again!!

  9. #69
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    3,731

    Default Re: Really bad compression #'s on one of my 225's.

    Well, that IS good news. I understand the issues with getting it all back together. My only advise is to take it slow and easy. Think through each process and make sure you have a good mental picture of what goes where - one step at a time.

    Please keep us posted on your progress.
    CHawk 25 DLX

  10. #70
    Join Date
    Apr 2016
    Location
    barnegat NJ
    Posts
    2,706

    Default Re: Really bad compression #'s on one of my 225's.

    Keep that manual handy and good luck

  11. #71
    Join Date
    Sep 2010
    Location
    Freeport, Texas
    Posts
    185

    Default Re: Update; RESOLVED. Really bad compression #'s on one of my 225's.

    Update: the story is concluded.

    Hello all.........it's been awhile. I had nothing to report because I hadn't been able to work on the boat for a long time. Finally, I have the moral of the story.

    It turns out that the valves were badly corroded on the stb motor. The cylinder walls looked good, but I couldn't see detectable cross-hatching, which left me concerned about the rings. Another boat came along that we really wanted, so we put the Stamas up for sale. Good boat, good price meant we had a buyer quickly, and of course, compression numbers were needed. The boat had been running perfectly, but I hadn't done compression since putting the reconditioned heads back on. I was a bit nervous.

    If you read the earlier part of this thread you know that numbers on the stb motor were bad, and the port motor was reasonable in the mid-180's.
    That test was done cold, in winter, on a cold day for Texas.

    This time we tested warm to mimic real life. I held my breath.....but no worries. All numbers on both motors were between 205-215. Corroded valves and seats were the problem. Beautiful!! The buyer was a happy camper and the boat is sold.

    Thanks to all who gave advice. It was much appreciated. I already miss having a boat. To tell the truth, the next boat we're looking at is a smaller
    cat with twin Honda 90's. Any comments about these motors? I believe they are the same year as the boat.....1997.

    I may be boatless, but I'm back on the forum. Thanks again........

  12. #72
    Join Date
    Sep 2008
    Location
    Hague, Virginia, USA
    Posts
    3,731

    Default Re: Really bad compression #'s on one of my 225's.

    Sounds like that's all worked out really well. Congrats on that.

    Can't comment on the 90's except to say that there have been very few posts about issues with those motors on this forum. Seem to be really solid. I think Hondadude has a got a good bit of experience with them and should be able to offer some opinions.
    CHawk 25 DLX

  13. #73
    Join Date
    Nov 2009
    Location
    temecula, ca., usa
    Posts
    2,674

    Default Re: Really bad compression #'s on one of my 225's.

    Sorry fellas, I don't always tune in to the "big" engine posts because I don't work on them. And I really haven't studied this thread thoroughly. But I see my name mentioned a couple of times so I feel compelled to chime in.

    As to the compression test question ie: hot or cold, it is my opinion that, at least initially, a compression test should be performed on a cold engine. My reasoning is based on the fact that compression is such an important component of starting a cold engine as well as the maximum amount of leakage will likely occur when all components are in an equal thermal state. Naturally, if you are ONLY interested in what the maximum compression each cylinder can produce, then the hotter the better. But from a strictly diagnostic and repair point of view, cold should suffice. Not to mention that I got really fed up with burning myself years ago trying to do ANYTHING on a hot hunk of metal!

    When I was growing up and trying to become a competent Detroit Diesel mechanic, that revered institution actually switched their philosophy from doing many things, like tune ups, valve adjustment, governor adjustment and so on from hot to cold. While they still have you obtain operating temperature to do a compression test, I found that the engine would cool considerably when shut down for injector removal and compression tester install. Plus, you don't use the starter to do the test, but run the engine each time you check a cylinder. So, it naturally heated up during the test. I found preheating the engine wasn't critical to obtaining the definitive information I was after. Also, as I stated earlier, what's the point of getting burned and being unduly uncomfortable while doing your job unless it yields vastly superior results?

    I'm POSITIVE I will get an argument from someone on this but I have to say "my way" worked just fine for me, and the many students I trained, for almost 30 years.

    As far as your leakdown test results btravlin2, I would think that you probably have some intake valves not sealing. The air entering the cylinder and exiting the adjacent spark plug hole indicates to me leakage into the intake manifold and then taking the path of least resistance. Of course this can only happen this way if the adjacent cylinder's intake valve is open or leaking itself. You can temporarily back off the rocker on that valve if it is sitting on the cam lobe to verify what is actually happening.

    I wish you and your tech good luck sorting it all out.

    JimmyD

  14. #74

    Default Re: Really bad compression #'s on one of my 225's.

    A compression test should be done based on the rules of the test, ie. it should give you the parameters like hot or cold, plus RPM, etc. Some may be done hot, some cold, whatever the test's instructions are.
    I'd say cold is more likely correct, since if it were hot, the temperature would be inconsistent over the time it took to do the test, depending on the speed. Cold is cold, stays the same for the whole test.

  15. #75
    Join Date
    Aug 2011
    Location
    South Texas
    Posts
    567

    Default Re: Really bad compression #'s on one of my 225's.

    You should also do it WOT.

  16. #76

    Default Re: Really bad compression #'s on one of my 225's.

    On a side note on the shimmy you describe .mine does the same thing on the muffs but not in the water. The mechanic said it was most likely because of the lack of back pressure while out of the water. Not sure how often the fuel trim changes though

  17. #77

    Default Re: Really bad compression #'s on one of my 225's.

    Before you do a compression check the motor needs to be warm let it idle for awhile .Then with the throttle body butterfly wide open do the compression test then double check your results with your compression results on here.

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