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Old 29 March 2018, 15:32   #21
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Country: Sweden
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Please Help what 70hp Carbs is best for my 50hp Yamaha?
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Old 30 March 2018, 01:59   #22
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Nice work on the exhaust, looks excellent!
I had Yamaha 70hp carbs on my tohatsu 50, the square bowl type. Might depend on your engine, if itís got round bowls then maybe go for the same in 70hp.
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Old 13 March 2019, 14:53   #23
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Milled head

Finally I have milled my head.3,5mm
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Old 13 March 2019, 14:55   #24
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The one I will use is the one with 3,5 mm taken off and new squishbands on.
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Old 13 March 2019, 14:59   #25
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More air and fumes

More airintake improvements.
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Old 13 March 2019, 15:01   #26
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70 Carbs with 150 Jets and more polishing and porting of intake and exhaust.
Also changed the lower bearing that always is the one most exposed.
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Old 13 March 2019, 15:13   #27
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Finally on boat

Now I have tryed my "new" motor and it goes really well but very loud.
It revs 7600 and I need a bigger prop.
The one put on is a Trophy Sport 10/8X15 and its to small.
Anyone out there with suggestions about what to buy?
I was thinking of buying :

https://www.ebay.com/itm/Mercury-25-...1:pf:0&vxp=mtr

I really dont know much about props so please help.
Do you have any thoughts or want to sell please let me know.

Cheers Fredrik
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Old 13 March 2019, 18:53   #28
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I'm curious why do you believe getting rid of the autolube will save you power? Certainly lots more hassle to premix for an umeasurable gain in hp.
Also isn't it a bit hit-and-miss how the new main jet size was determined? Also never heard any of the 80's two stroke tuning firms recommending removing the reed stops. Important that they are there to prevent metal fatigue - you are on borrowed time.

Shameless sales plug if anyone wants to buy my Yamaha 350 YPVS Stan Stephens Stage 3 kit comprising barrels, heads, 36mm reverse slide TZ350 Mikuni carbs with YZ125 6 petal reed blocks with adaptors and Swarbrick expansion chambers complete with jetting kit and modified airbox and throttle cable then I might be open to offers. I estimate it was good for 70hp about the same performance as my Suzuki RG500. Pipe design (specifically stinger dia and length) controls peak revs, power band was 10K to 13K instead of 6K to 9.5K rpm, welded crank essential. Marine engines are in a very low state of tune in comparison. Seems much tuning knowledge is lost nowadays but us old timers still have it lol.
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Old 14 March 2019, 01:29   #29
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Loving your work, the heads look excellent. The cowling vent looks like what I had on my old tohatsu. What sort of speed are you getting with the 15p trophy? I've tried one of them on my 70hp and the tohatsu 50hp, ran well but a bit too much bow lift and not enough speed, decent torque though. If you are running dual stage reeds you don't need the stops, if they are single stage I would recommend leaving the stops on especially at the RPM you're getting now.
Removing the autolube is a good idea, if you are pushing the engine higher than standard it needs more oil for the bearings.

I would avoid Ron Hill props, they are hit and miss, some are good but most are bad. Some just need work but others are so far out they cannot be fixed, different pitches between blades etc. not good quality.
I've got one Forge V1 left I would sell, 11.25x18p 13 spline. Fully blueprinted, heat treated ready to go
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Old 14 March 2019, 14:27   #30
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Reeds and prop.

Thanks Roflhat for your feedback, really appreciate your thoughts.
Your prop looks very nice and perhaps you can make contact and give me your price?

heffak@hotmail.com

The one Im using today is Trophy Sport 15P and my estimated max speed is around 45 knots.
Dont know if my reeds are single or dual stage? Think they are dual but maybe you can tell?
My reeds are Boysen B322 and you can have a look at the pictures.

Cheers heffak
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