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Thread: Old HotRodder

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    Default Old HotRodder

    I have to confess, I don't race boats, although I have watched a couple on the Mississippi up here in Minnesota. I am an old racer though. This was my last race car in 1970

    About 8 years ago I discovered classic fiberglass boats, and had to jump in. My first was a 58 Glastron FireFlite with a 75 Johnson. I made it into a hot rod with rolled and pleated interior, and lace paint. I hopped it up by putting a 50 horse hood on it.

    Then a 75 Larson All American
    with a 35 Johnson

    and now I'me working on a 59 Classic Barricuda that I'm putting 2 35 Johnsons on.

    Well maybe I should just rebuild them and leave them alone, but the hotrodder in me says "there must be a few more horses in there just waiting" I looked through the great web and ended up here. I read about the two-cycle tuners hand book and looked for one to buy. I found one in great condition for $999. More knowledge than I wanted. But after reading a little more found one to download, but the math is a killer. I really don't need to go that fast!!!

    Here's my question to the experts. I want to mill the head, How much can I take off without turning it into a race motor? If I oval out the exhaust port how much? I want a couple good running motors that stay together, but give me a little more punch. Or should I just leave well enough alone?

    I hope someone has an answer for an old hotrodder.

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    Sam Cullis Mark75H's Avatar
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    You can do a lot to the motors, but the limiting factor is their lower unit.
    Since 1925, about 150 different racing outboards have been made.


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    Team Member JohnsonM50's Avatar
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    Quote Originally Posted by 50sFlash View Post
    I have to confess, I don't race boats, although I have watched a couple on the Mississippi up here in Minnesota. I am an old racer though. This was my last race car in 1970

    About 8 years ago I discovered classic fiberglass boats, and had to jump in. My first was a 58 Glastron FireFlite with a 75 Johnson. I made it into a hot rod with rolled and pleated interior, and lace paint. I hopped it up by putting a 50 horse hood on it.

    Then a 75 Larson All American
    with a 35 Johnson

    and now I'me working on a 59 Classic Barricuda that I'm putting 2 35 Johnsons on.

    Well maybe I should just rebuild them and leave them alone, but the hotrodder in me says "there must be a few more horses in there just waiting" I looked through the great web and ended up here. I read about the two-cycle tuners hand book and looked for one to buy. I found one in great condition for $999. More knowledge than I wanted. But after reading a little more found one to download, but the math is a killer. I really don't need to go that fast!!!

    Here's my question to the experts. I want to mill the head, How much can I take off without turning it into a race motor? If I oval out the exhaust port how much? I want a couple good running motors that stay together, but give me a little more punch. Or should I just leave well enough alone?

    I hope someone has an answer for an old hotrodder.
    Thats a cool boat. Those older 35s were a good running long lasting motor but were not real fast. Even so theres alot of motor on board so you could leave em stock, work on set up, hull drag & weight. Those will get you a little but the biggest increase would be from props. Being that you need 2 is more of a challenge to find. With 2 motors you could technically spin a prop pitched for near 70 hp. Since if you had a 70 it would spin 1 prop somewhere less would be a happy medium. You would most likely need to have custom mades for the lack of availability or just get the hi-est pitch stock props made. If possible youll want $tainless steel, will out run & accelerate a comparable aluminum 1. With some work & testing you should get into the 40s no problem, maybe more all things being optimal. With 2 props spinning the same way you will want to watch for handling issues like it wanting to bite real hard it a left turn. [unles they counter rotate] Good Luck, Mike

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    Sam Cullis Mark75H's Avatar
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    Quote Originally Posted by JohnsonM50 View Post
    Those will get you a little but the biggest increase would be from props. Being that you need 2 is more of a challenge to find. With 2 motors you could technically spin a prop pitched for near 70 hp. Since if you had a 70 it would spin 1 prop somewhere less would be a happy medium. You would most likely need to have custom mades for the lack of availability or just get the hi-est pitch stock props made.
    Even custom made high pitch props will not overcome the shortcomings of the poor shape of these lower units.
    Since 1925, about 150 different racing outboards have been made.


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    Team Member JohnsonM50's Avatar
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    Quote Originally Posted by Mark75H View Post
    Even custom made high pitch props will not overcome the shortcomings of the poor shape of these lower units.
    Yeah their not that streamlined but my experience with that type motor is that from an average set up starting point -some- improvement can be realized.. If set less deep w/ better more pitch less dia. props. Theres no shortage of torque either to go with.

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    Sam Cullis Mark75H's Avatar
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    Mike, these are completely insensitive to how deep they are, they are that bad.
    Since 1925, about 150 different racing outboards have been made.


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    - Skoontz's Avatar
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    Cool looking boats. If you want to mill the heads of your 35's, you can safely take .040 from most of the pre 1970 motors, but, don't use that as etched in stone. Get some modeling clay, or soft lead, run the pistons to TDC, then mic the clay of soft lead. We have taken .100 from some heads where others .040 is as close as you want to be.

    But, I echo what Sam said about the hydro dynamics of the gear cases on those motors. Without doing something there, anything you do up top will be insignificant.
    Bill Schwab
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    Team Member JohnsonM50's Avatar
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    Quote Originally Posted by Mark75H View Post
    Mike, these are completely insensitive to how deep they are, they are that bad.
    I cant argue that they arent that bad, as is.. they are. I have done work with one similar, starting out at 34 on a utility & eventually got 46 from it [same boat]. By then it was thinned to the breaking point & I put a cone on it. It also has a speed prop adapted. Definitly not the same as what I started with but the same hunk of junk- changed a little . Very limited as you say tho, running the powerhead above 6200 helped a little too.

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    Thanks guys. I'm use to Merc guys dissin' my Johnsons, but I don't have any Speedmaster units for them, so we "run what ya brung" I have a 16 1/2" transom. I worry about going higher because I don't want remote water pick-up. I have a friend that has a prop shop and will bend the aluminum ones till I find something special cheap. (cheap is the important part) and a friend with a company called "Metals Joining Lab" He can weld anything, so I could add a nosecone. Sounds like that might help.
    How much piston to head clearance should I have? The pistons are so far down I can't believe there's any amount that could bring them too close. I have also seen "hi compression" head gaskets. Are there different thicknesses? How about "cleaning up" the ports?
    You guys are great.
    Thanks
    Jerry

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    Team Member JohnsonM50's Avatar
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    Quote Originally Posted by 50sFlash View Post
    Thanks guys. I'm use to Merc guys dissin' my Johnsons, but I don't have any Speedmaster units for them, so we "run what ya brung" I have a 16 1/2" transom. I worry about going higher because I don't want remote water pick-up. I have a friend that has a prop shop and will bend the aluminum ones till I find something special cheap. (cheap is the important part) and a friend with a company called "Metals Joining Lab" He can weld anything, so I could add a nosecone. Sounds like that might help.
    How much piston to head clearance should I have? The pistons are so far down I can't believe there's any amount that could bring them too close. I have also seen "hi compression" head gaskets. Are there different thicknesses? How about "cleaning up" the ports?
    You guys are great.
    Thanks
    Jerry
    Dont worry, Johnrudes are good for different reasons aaannd there may be a few that are faster than their Merc counterpart.

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