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Thread: Building a Super Mod 2 cylinder Mariner/Yamaha

  1. #31
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    Quote Originally Posted by Mark75H View Post
    The boat and the prop
    Mark YES that is part of it for sure. But, props are much better now than they were back then so the advantage has to be with us prop wise. Second in the case of the Japan tunnels. Those tunnels were no where close to being as well designed as the tunnels we tried. So the advantage has to be with the newer boats. Here is another bit of history. In the early 1990's Brad Collins Mirage Boats teamed up with Hydro Tec and did a boat and motor to race in that series. I don't think they got it competitive?? We have raced many Tohatsu's and Yamahas over the last 20 years. In the case of the 50 and 60 hp motors, we could never get the 2 cylinder models to perform as well as the 3 cylinder. Case in point is Formula 50. The top motor was the 50D Tohatsu and it did run in the 80 mph range. I have a lot of respect for the overseas race group. Maybe they can let us in on some secrets.

  2. #32
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    Here's a W60 Mariner in Iowa... (not mine)

    https://waterloo.craigslist.org/bpo/5165025470.html

  3. #33
    Team Member hydrospeed77's Avatar
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    Hounddog,
    any updates on this project? I'm interested in getting a 1977-1979ish Mariner 60 2cyl running well.

  4. #34
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    This project is an on going challenge and I still are NOT where I would like to be.
    In brief here is an up-date.
    - the motor I wanted to end up with is the original race version..model 6F1..it was only made one year. It had two stainless steel exhaust pipes similar to the single pipe on a 70CES...I have not seen them so I am not sure this is true.
    - I purchased a new old stock 6F0 powerhead It was only made one year. It had a narrow exhaust pipe with an outer shell similar the the stock 70 Yamaha and not the large single piece system on the normal 48. 55 and 60 Yamaha.
    - The motor had sat a long time and I could see a rust line on the cylinder walls so I removed the head to clean them up.
    - Big surprise! This powerhead uses different gaskets...ends up there are several different blocks and they use different gaskets...took a year to get the gaskets.
    - I followed the parts book picture to build an exhaust.
    - I tried to use 90's ignition only to find the block bosses to attach the stator plate were in the wrong position.
    - When I mounted the side cdi and coil assembly..the cowl did not fit.
    - the driveshaft was 3/16's too long.
    - I got what was to be an original lower unit from Finland only to find the drive shaft a smaller diameter and the gear case similar, it would not fit my mid section.
    - then a find a YouTube video of a 6F1 motor pulling a tube....in sounds none racy and nothing special
    I am taking a break from the project!
    Likes Xtoffer72 liked this post

  5. #35
    Team Member Roflhat's Avatar
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    I can't believe that you would get near 3 cylinder (70ces) performance from a 2 cylinder. When you're tuning the 3 cylinders it's extremely effective because the cylinders are 120 degrees apart, hence why 3 cylinders and V6's are so popular.

  6. #36
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    I was not trying to get the 2 cylinder to outperform the 70CES. Initially I was looking for information on the mod 2 cylinder motors they raced in Japan. I could not find any. During the search I found the 6F1 motor which raced prior to the 70CES as a T850 and later as a T750 motor. Racers had many good things to say about them. We race T750 here and this motor is legal in stock form. That is why my focus switched to building a stock motor. The limited production and lack of common replacement parts such as gaskets was a surprise. I have not heard from anyone that still has a complete original 6F1 motor. So far they all have other powerheads which have replacement parts available.

  7. #37
    Team Member hydrospeed77's Avatar
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    I'd be interested to see if this 2Cyl outperforms a 3cyl 700cc 50hp. Both in stock form and just with basic mods like larger carbs, clean up the ports, mild exhaust tuner.

  8. #38
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    Quote Originally Posted by hydrospeed77 View Post
    I'd be interested to see if this 2Cyl outperforms a 3cyl 700cc 50hp. Both in stock form and just with basic mods like larger carbs, clean up the ports, mild exhaust tuner.
    I can answer that question. Based on our race experience here in T750. The 2 cylinder OMC motors outperform the 3 cylinder Tohatsu. APBA does not allow the 2 cylinder OMC to race in D class against the Mercury and Tohatsu for the same reason.

  9. #39
    Team Member hydrospeed77's Avatar
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    Quote Originally Posted by Hounddog View Post
    I can answer that question. Based on our race experience here in T750. The 2 cylinder OMC motors outperform the 3 cylinder Tohatsu. APBA does not allow the 2 cylinder OMC to race in D class against the Mercury and Tohatsu for the same reason.
    I was not thinking OMC at all. Yamaha 2Cyl 55 / Mariner 60 vs. Yamaha 700cc 50. Of those two, what would run better in T750..?

  10. #40
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    Based on Thundercat and APBA Formula 50 racing the Tohatsu 50D is superior to the 50 hp Yamaha. We have not had a 50 Yamaha race in T750 here. The Tohatsu has the speed record in T750 at near 66 mph overseas. Based on our testing here we cannot get 60 mph with a Tohatsu. We had a stock 55 hp mariner/Yamaha run on a Delta. It ran in the 55 mph range same as the stock Tohatsu, so they would be close in top speed. I would give the edge to the 2 cylinder on the race course because it has more punch out of the corner.

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