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  1. #31
    As you hopefully can see from the pictures of main transfers for one cylinder on my "in the closet 88 115 block", there are no traces from secondary machinings, just the straight and smooth results from one mill operation to create each port opening. Any thing else I think would be an impression coming from the shapes of the castings.

    Size of mill and port is, as suggested by "baldad45", a bit more than 7/16" though. From the tools I had at hand I would say mill size is 9/16" or very close to this, which is also port height.





    A note on bleed restrictors:

    I have seen the importance of the small plastic bleed restrictors in place in their channels being mentioned here and elsewhere in the past, as well as it is pointed out in the Merc Service Manual. However, of the three late inlines of mine that I have been into, there has not been one single bleed restrictor in place in any of these engines. And at least one of them, a 88 115 used on my boat until two years ago, was still a very good and reliable idler.

    So either all fifteen of them small restrictors have came loose and been ingested by the engines or, more likely, there has never been any bleed restrictors in my holes. If you look at the bleed hole entrance in my pics above, you will see it appears someone (read Mercury) has hit it with a punch or something. And this is how all cyl 1 to 5 holes in my engines looked. I think the punch was done to create a restriction being small enough, and also one that will not fall out.

    When I rebuilt my 84 power head I put plastic restrictors in though, probably unnecessary but they are indeed affordable and according to the parts list they should be there. But to do so I had to first clear the holes out (really a bit more than so) with a proper size drill bit. No improvement though compared to the 88 115.

    PL
    Last edited by petlun; 02-27-2011 at 01:17 PM.

  2. #32
    Will you post the patent paper on the banjo reeds ?
    Here is that paper:











    PL

  3. #33
    Join Date
    Jul 2005
    Location
    Regina SK. Canada
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    511
    Thanks!

  4. #34
    Here is a paper on design and manufacture of the aluminum reed blocks.

    I found it interesting as it explains why the small step after the radius below (before) the membrane (Fig. 6) is there: Only as a second to best solution, necessary to deal with variances in production! The shape of desire is the one in Fig. 2 though.







    PL

  5. #35
    Join Date
    Jan 2010
    Location
    Melbourne, Australia
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    14
    Can the reed blocks from an 84-88 90hp be used in an 84-88 115? What would be the effect of this?

    Alternatively can reed blocks from an early 150 be used in an 84-88 115?

    Thanks Gary

  6. #36
    Join Date
    Nov 2001
    Location
    South Carolina
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    2,595
    The 90 blocks will choke the engine. If you use the 150 blocks you will be OK. Best bet is to open all the reed ports, as the 150, and use the banjo reeds.
    Never argue with an idiot. They drag you down to their level, then beat you with experience.

    3 X APBA Formula V Nat'l Champion
    APBA Formula V US-1
    It took me 29 years to become an overnight success.

  7. #37
    Join Date
    Jan 2010
    Location
    Melbourne, Australia
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    14
    Thanks Jeff. My engine is 1988 115 and appears that sometime in its life has had 90hp reed blocks fitted. From your comments I take it you recommend the 10/10 reed blocks from 150, not the 10/8, is that correct? Is it possible to modify the 90hp reed blocks to take the 150 reeds and stops, or just replace the whole lot?

  8. #38
    Quote Originally Posted by garyg View Post
    Is it possible to modify the 90hp reed blocks to take the 150 reeds and stops, or just replace the whole lot?
    You can reuse the reedblocks.. just replace the reeds and reed stops, use the "banjo" type reeds .

    34-65319 reed stops, used on the 1500/1400 + the 10 petal side on the late 115 8/10 reedblocks..
    34-65312A1 reeds, used as above...

    Arne Kjetil
    My engines :
    Johnson V4m-10s 90 hp 1964,from the prosess.
    Mercury TII, next project
    True story ??:-)

  9. #39
    The 10/8 reed block units were probably developed to reduce excessive "short-circuiting" (amount of fresh air/fuel charge dumped as waste out into the exhaust ports) from cylinders 2, 4 and 6.

    As a result less fuel was consumed with power (basically?) unaffected.

    The 10/8 reeds were used only in the 1983 to 88 115īs.

    PL

  10. #40
    1972 1400



    1976 850xs



    1977 1500
    Last edited by Capt.Insane-o; 01-12-2011 at 05:06 PM.

  11. #41
    Join Date
    Nov 2001
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    South Carolina
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    2,595
    The 140 and 150 were the same block.
    The 10/8 block was developed for fuel economy being that gravity pulled more fuel down than up. More even flow of quantity.
    Power was already decreased with the low dome pistons of 1978, so yes additional fuel was not needed. If one were to go back with high domes opening the reed blocks back up would be advisable.
    Last edited by Jeff_G; 01-13-2011 at 10:30 AM.
    Never argue with an idiot. They drag you down to their level, then beat you with experience.

    3 X APBA Formula V Nat'l Champion
    APBA Formula V US-1
    It took me 29 years to become an overnight success.

  12. #42
    Join Date
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    Location
    Annapolis, MD ragboat capital of the world
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    The late 140 was the same as the 150. The 1972 140 had the Direct Charge pistons and improved exhaust, but didn't have power ported pistons and the matching cylinder machining

  13. #43
    Mk75H: "The 1972 140 had the Direct Charge pistons and improved exhaust, but didn't have power ported pistons and the matching cylinder machining"

    ...and the 72 1400 also had ordinary reeds rather than banjos.The std 1973 to 77 1500īs (non XS/J-blocks and also excluding some may be square ports early 1500īs), the 78 1400 and the 1979 and 1980 140īs are, in all aspects affecting power that were otherwise changed by Mercury in the DC inlines (porting, reeds and exhaust tuning), the same engines.

    Low deflector pistons were used from late 1977 or 78. Compression was reduced from like 6.70 to around 6.52, a difference I very much doubt could be detected in speed or fuel efficiency by any normal human being out in a boat. But IF there would be a detectable difference between high and low domes, I am convinced it comes from the higher deflector being better in doing what itīs there for: Block off short-circuiting of fresh gases out into the exhaust.
    The height of the high deflector was obviously the height considered necessary to do a good enough job when the Direct Charge system was designed.

    The 1981 and 82 115īs are very much the same engines as the 73 to 80 1500/1400/140īs, but the 115īs had ordinary (non banjo) reed units wich means they are a little shy on power compared to the earlier 1500/1400/140īs.
    Power rating of the 81 115 engine (being internally exactly the same engine as the 82 115) are 81 kW at THE CRANK according to ISO-3046 and at the same time also 115 hp, also at the crank, but according to BIA-310_77.
    In the 1982 brochure Mercury however says the 115 now is 82 kW at THE PROPSHAFT (!??) according to ICOMIA 28.
    Remember though the 1981 and 82 115īs are, as said, internally the same engines. But 81 and 82 are the transition years from crank to propshaft ratings for Mercury.

    For 1983 Mercury used the new "10 banjo membranes upwards and 8 std membranes downwards reed units" in the 115 engine. Power rating was however unchanged at 82 kW (110 bhp) at the prop but the brochure says "The improved torque and acceleration makes the 115 the perfect engine for water skiing." (Brochure is a Swedish translation though, so this means itīs English to Swedish and then back again by me.)

    For 1984 a new two channel and much longer than before exhaust tuner was used. Power rating was now finally up to 86 kW at the prop, which is 115 bhp.
    No more power affecting changes were made to the late 6 cyl. 115īs, so these figures are valid 1984 to 88.

    PL

  14. #44
    This 72 has banjo reeds.

  15. #45
    If you check post #32 you can see they were not yet developed for the 1972 model year production.

    Developement of the banjos were, according to the paper, done on one or several 72 1400īs as test engines/"mules".

    But of course a later upgrade to banjos on a 72 1400 should have been possible.

    By the way; have you checked heights and positions of ports in your pics?

    PL

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