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Old 13 July 2016, 04:37   #11
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Bell housing suggestion is a good idea as plenty mercruiser bits about you could then swap to merc steering ram too.
I'd imagine if the trim sensor needs to be in the system then you could leave it plugged in somewhere in the engine bay to give the system a static reading which should work
If you want the trim gauge it's no big deal to wire in a merc resistance gauge to the dash
That's assuming the merc trim sender is different resistance but easy to check with a meter
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Old 13 July 2016, 07:36   #12
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Quote:
Originally Posted by vdubr928 View Post
.....
....I do not know the current ratio or how to find it but I know mine is a 300hp 7.4 and was turning a 16x16.
Turn the drive input shaft with the drive in gear until the prop turns one full turn. Keep track of how far the input shaft turns and this will give you your ratio. EG: Input shaft 1 1/2 (1.5) turns - prop (output shaft) 1 turn will equal 1.5:1

If the drive is in gear, simply turn the engine instead of the input shaft. Be sure the engine can't start!!
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Old 13 July 2016, 08:02   #13
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alpha is said to be good for 450hp petrol
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Old 13 July 2016, 18:04   #14
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Quote:
Originally Posted by jwalker View Post
Turn the drive input shaft with the drive in gear until the prop turns one full turn. Keep track of how far the input shaft turns and this will give you your ratio. EG: Input shaft 1 1/2 (1.5) turns - prop (output shaft) 1 turn will equal 1.5:1

If the drive is in gear, simply turn the engine instead of the input shaft. Be sure the engine can't start!!
Won't work on a hydradrive they need to be spinning to get the oil pressure to engage the clutches
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Old 14 July 2016, 11:32   #15
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Country: USA
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Engine: Yamaha 7.4 Hydradriv
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You guys have made my year. I was very worried when I started having trouble. Nobody in the US has accurate info about this. I bet there are hundreds of these things in scrap because people don't know this is possible. I'm going to start collecting parts. I want to go with a Bravo 2 so I can probably make the stock Yamaha raw water pump (mounted on engine) work. I can still easily get the impellers for it.

Yam Man, I curious about your comment on the trim sender. My Yamaha has the Delco EST ignition. I don't know if that is the same as yems? Can you explain a little? I am a low voltage guy so I may be able to work around this or just trash the est and go with a mechanical advance.
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Old 14 July 2016, 11:33   #16
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Originally Posted by jwalker View Post
Turn the drive input shaft with the drive in gear until the prop turns one full turn. Keep track of how far the input shaft turns and this will give you your ratio. EG: Input shaft 1 1/2 (1.5) turns - prop (output shaft) 1 turn will equal 1.5:1

If the drive is in gear, simply turn the engine instead of the input shaft. Be sure the engine can't start!!
Being a Hydrostatic drive, this is impossible. It sounds like I have a 1.50:1 setup since I have a petrol engine.

Edit, This was already mentioned above. Not sure why i didn't see all the posts when I came in this morning,
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Old 14 July 2016, 11:58   #17
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If your going bravo two you will need to down pitch to around 2.0:1ratio due to the large diameter prop on the bravo
Your already on a fine pitch prop so I'm guessing it's a big heavy boat?
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Old 14 July 2016, 12:28   #18
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Originally Posted by beamishken View Post
If your going bravo two you will need to down pitch to around 2.0:1ratio due to the large diameter prop on the bravo
Your already on a fine pitch prop so I'm guessing it's a big heavy boat?

So should I just stick with a Bravo 1? I'm sure it will handle 300hp.

It is a big cruiser. It had a 16x16 on it. I put the 13 on there to help it get out of the water. I suspect a bearing issue in the drive is generating the extra heat that is causing this issue. It may be that the 16x16 was fine and the low WOT RPM was caused by drag inside the drive due to whatever bearing is failing.

I have read it is advantageous to run a larger diameter prop on a cruiser but I am not very knowledgeable about this. I'm a car guy with pretty good mechanic skills but this boat stuff is new to me.
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Old 14 July 2016, 12:40   #19
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Bravo 2 or 3 will be best for a big cruiser due to the bigger blade area but in reality any of the bravo range will do they all have there plus and minus points
Mercury have a good prop calculator which will give you the best ratio and prop size for your set up
I think personally I'd go for 2.1 bravo 2 but props are expensive for them and much cheaper for bravo 1 and more readily available
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Old 14 July 2016, 13:17   #20
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Quote:
Originally Posted by beamishken View Post
Bravo 2 or 3 will be best for a big cruiser due to the bigger blade area but in reality any of the bravo range will do they all have there plus and minus points
Mercury have a good prop calculator which will give you the best ratio and prop size for your set up
I think personally I'd go for 2.1 bravo 2 but props are expensive for them and much cheaper for bravo 1 and more readily available
Mercruisers Prop Calculator doesn't go back past 2000. That will be a much higher HP version of my engine. I would't mind the expense of the bravo 2 props if I can get it right the first time. :-)
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