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  1. #1
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    Finally got around to a compression check today (bad)

    I've been through a lot trying to figure out why I can't get my 96' johnson 200 venom over 52 mph at 5800 rpms. Been a little nervous to do a compression check but really didn't expect the low readings I got today. Warmed her up first and here are the readings..72,70,62 lb....75,80,75 rb. It seems really happy and smooth around 5800 rpms but does take a bit to get started. Can these readings be the reason I can't get decent top speed? Model is J200stledm and currently running Raker HO 14 1/2 x 23P. Any thoughts?

  2. SC Club Moderator ChampioNman's Avatar
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    #2
    Has this issue just started or has it been like this all along? I would recheck them with a different gauge. I would also check and make sure the throttle plates are opening fully at WOT. The bottom two throttle bodies are attached by two couplings that may loosened. Make sure the clear sleeve is still intact on the throttle roller where the timing arm makes contact.

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    #3
    Quote Originally Posted by ChampioNman View Post
    Has this issue just started or has it been like this all along? I would recheck them with a different gauge. I would also check and make sure the throttle plates are opening fully at WOT. The bottom two throttle bodies are attached by two couplings that may loosened. Make sure the clear sleeve is still intact on the throttle roller where the timing arm makes contact.

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    #4
    Raker HO is a very aggressive prop - the best prop I ran on the same motor you have was an original raker. You can see the tip cup on the HO vs the original is very different. My old motor over time went from being a 62mph motor to a 57 mph boat. I think it was just getting worn out.
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    #5
    Quote Originally Posted by Cobrafisher View Post
    I've been through a lot trying to figure out why I can't get my 96' johnson 200 venom over 52 mph at 5800 rpms. Been a little nervous to do a compression check but really didn't expect the low readings I got today. Warmed her up first and here are the readings..72,70,62 lb....75,80,75 rb. It seems really happy and smooth around 5800 rpms but does take a bit to get started. Can these readings be the reason I can't get decent top speed? Model is J200stledm and currently running Raker HO 14 1/2 x 23P. Any thoughts?
    Rakers are even numbers? Renagade 4 blades are odd pitch. You running a 24 on that 200hp?
    1996 Stratos 201 pro xl
    1996 Johnson Faststrike J150GLEDB

  6. SC Club Moderator ChampioNman's Avatar
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    #6
    Quote Originally Posted by ScottOz View Post
    Rakers are even numbers? Renagade 4 blades are odd pitch. You running a 24 on that 200hp?
    Not on a Raker 2 prop they are odd and even pitches. They are different from the original Rakers. The prop was designed for the Etec motors. Never had much luck on a Looper carbed motor with the R2.

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    #7
    Yes it has been this way since I bought it about a year and a half ago and I've been working on it here and there and trying to figure things out. The Raker prop is a 22..sorry. I'll check the throttle plates tomorrow and see if I can get a hold of another compression tester. I've ran this motor with 3 different props now and the top speed is the same. The origional prop an old OMC shooter, a Solas 4 blade and now the Raker...the 4 blade and Raker have better hole shots with the Raker being the best. The motor has power, it'll push the boat up on plane really fast but not much top end.The boat itself is really comfortable to drive and fish..lots of room for everything. I can be on the water all day and still not want to get off the water. If only I can figure out this motor. If the compression is really that low would it be able to get up on plane like it does very quick?

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    #8
    might do a decarb and see if it helps readings?
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    #9
    That's one of my next moves

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    #10
    Quote Originally Posted by ChampioNman View Post
    Not on a Raker 2 prop they are odd and even pitches. They are different from the original Rakers. The prop was designed for the Etec motors. Never had much luck on a Looper carbed motor with the R2.
    Interesting Thank You Fred. Yep I only run the old school motor for now. By the way. She is running really good.
    1996 Stratos 201 pro xl
    1996 Johnson Faststrike J150GLEDB

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    #11
    I pulled the heads today and they just fell loose when I got the bolts loose enough. Not sure if thats supposed to happen or not. It's very obvious the gaskets have been leaking and the piston in the cylinder with 62 psi has pitting as well as the head in same place. The heads are in very good shape actually and all pistons look good other than a little water getting in. The mating surface of the block is covered in rust.The head bolts definitely were not torqued the same, some easy to get loose and some very tight. Some of the bolts look brand new and some are covered with corrosion and some caked on oil. Ohhhh! and the pistons are .020, this motor has been rebuilt. So assuming the motor was rebuilt correctly, could the head bolts back off by themselves or did someone just do a bad job of assembling and torqing the heads? At any rate I have cleaned the heads and have gaskets on order. Are clean mating surfaces and new gaskets going to bring my low compression up to a decent level, could the leaking gaskets cause my compression to be so low?

  12. SC Club Moderator ChampioNman's Avatar
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    #12
    yes

  13. Sprint Boats Moderator Bassmeister's Avatar
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    #13
    The torque pattern is on the heads follow religiously and retorque after a couple heat cycles....

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    #14
    Just getting around to getting the heads back on in the morning..how long should the heat cycle be?

  15. SC Club Moderator ChampioNman's Avatar
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    #15
    10 hours.