ill informed boat knowledge

[roscoe]

Re: ill informed boat knowledge

Use a torque wrench.


done now.

 

[achris]

Re: ill informed boat knowledge

Any grease is better than no Grease !!!

Agree...

Use a torque wrench.

But what about nuts and bolts that can't be accessed from the top? Do we have a 'side-ways' torque wrench?

 

[agallant80]

Re: ill informed boat knowledge

I was at West Marine this week and they had this prop chart. It said when going from 3 blade or from aluminium to stainless steel go down a pitch. Though I agree with some of the other posters here, prop pitch and matieral will yeald results based on more factors than just that. As for DP being slower, after reading through the posts that is also open depending on what you consider slower. at WOT from what I see it is about 2mph slower but interms of accelration and getting on plain its faster, though now some for the 4 blade props are claming some of the same bennifits. It would be interesting to see a performance test of an alpha with 4 blades vs a bravo III

 

[agallant80]

Re: ill informed boat knowledge

For the record I don't think I know everything. Just firgured it would be a good discussion to sort some of these things out.

 

[Friscoboater]

Re: ill informed boat knowledge

Just like someone said before, there is going to be alot of opinions on this. There are many different ways to look a things, and then there is just plain wrong advice. Finding a clear line is hard.

 

[achris]

Re: ill informed boat knowledge

I was at West Marine this week and they had this prop chart. It said when going from 3 blade or from aluminium to stainless steel go down a pitch. Though I agree with some of the other posters here, prop pitch and material will yield results based on more factors than just that. ...

Blanket statements like that are usually made by people with little or no knowledge of the subject matter...

The correct statement should be something like. When selecting a new propeller, find a pitch that will allow the engine to reach the manufacturers' recommended maximum rev range at Wide Open Throttle.

Nothing more, nothing less. Using the same pitch prop or one higher or lower should only be a starting point to finding the right prop as per the statement above....

Chris.......

 

[bruceb58]

Re: ill informed boat knowledge

Yeah, I did... Just threw that in for fun.....

Ah, what didn't show up too well was the wiki link... Sorry about that....

And the sad thing is, I started out college as a Chem major.

 

[bruceb58]

Re: ill informed boat knowledge

I was at West Marine this week...

Mistake #1

 

[bruceb58]

Re: ill informed boat knowledge

But what about nuts and bolts that can't be accessed from the top? Do we have a 'side-ways' torque wrench?

You mean like this?

 

[aspeck]

Re: ill informed boat knowledge

Blanket statements are ALWAYS wrong... wait, that was a blanket statement, so are they right? :lol:

 

[QC]

Re: ill informed boat knowledge

I'm taking my information from a Mercury Marine release on MCM Model year SN range, posted by DonS a few years ago.

MCM Model year SN range - Download - 4shared - Don S

Have a look at page 74 (the 82nd page of the PDF) about half way down. Sub-note 'a'....

Very odd. I have the same doc. Use it almost daily and never saw that note. However . . . the ratings don't change which indicates that Merc has developed a zero parisitic loss drive across the range. Considering that is virtually impossible, my puzzler is all squinched up. All of their marketing docs still say Propshaft. I have a contact that I am going to check with. Super duper strange.

Edit: It does say that the horsepower doesn't change, just the point of measurement. That could mean they calc the drive losses back in. None of that explains the different inboard ratings which is also puzzling . . .

 

[QC]

Re: ill informed boat knowledge

Blanket statements are ALWAYS wrong... wait, that was a blanket statement, so are they right? :lol:

No it's YOUR blanket statements are always wrong

Glad I could help.

 

[smokeonthewater]

Re: ill informed boat knowledge

fresh clean CHEAP oil is better than dirty old EXPENSIVE oil.

 

[UncleWillie]

Re: ill informed boat knowledge

And the sad thing is, I started out college as a Chem major.

Don't blame yourself.
The US and Canada are arrogant enough to spell it Aluminum and Pronounce it "Al uu min um".
The Rest of the world thinks it is Aluminium "Al you min ee um".
But we in the west seldom pay any attention to what the rest of the world says anyways!

Don't get me started on the Glacier issue. "Glass ee er" vs "Gla sher"

 

[roscoe]

Re: ill informed boat knowledge

Agree...



But what about nuts and bolts that can't be accessed from the top? Do we have a 'side-ways' torque wrench?

Yes !! There are open-ended torque wrench kits.

 

[roscoe]

Re: ill informed boat knowledge

Blanket statements are ALWAYS wrong... wait, that was a blanket statement, so are they right? :lol:

I have a blue blanket.

 

[TilliamWe]

Re: ill informed boat knowledge

:. . .

The dual props versus single prop is that at the high-end, a single prop will get you more speed ( WOT ) due to less 'drag'. The dual prop will beat the single out of the hole...

I know this statement to be true. How? Because we switched outdrives between two boats one afternoon. The B3 got out of the hole quicker, both times. And the B1 boat was faster on the top end (55+mph), both times.

 

[TilliamWe]

Re: ill informed boat knowledge

The benefits of Duoprop - The benefits of Duoprop : Volvo Penta

I see what they think, but my actual testing showed differently, on a Mercruiser. ^^^ Maybe that's just Mercruiser?

However, there has to be something to extra blades causing extra drag, and thus lower top speeds. Don't drag boats still use 2 blade props?

 

[bruceb58]

Re: ill informed boat knowledge

However, there has to be something to extra blades causing extra drag, and thus lower top speeds. Don't drag boats still use 2 blade props?

Completely different scenario since prop RPMS and boat weight are different and the fact that the prop isn't completely in the water.

 

[emilsr]

Re: ill informed boat knowledge

100 HP might be good for 10 MPH. What was the top speed with 425 HP?

BoatTest got 66mph running in salt water. In fresh water, I've seen as high as 67 on GPS but that was running with the cuddy stripped out in cool weather. Warm weather, half a tank of gas, couple of people, gear and it's a 63-64mph boat at lower elevations. In good conditions the same boat with the 525 runs 73-74. With the 600SCI, 80-ish. All 3 boats running "standard" prop shaft depth of 6" below the keel with no extension box. Is a pretty close comparison, and indicates that 10hp is worth well under 1mph in this particular boat, and/or there's way more than 100hp difference between the "425" and the 525.

A few years ago, a guy named Bob Lloyd did some prop shaft dyno testing on the 496magHO/Bravo X. Here's what he wrote:

We made a total of 4 pulls all within a couple of HP of each other. Final prop shaft HP was 387.8 at 5000 RPM, using SAE Standard correction method.

That seems to indicate the advertised power rating of 425 on the 496magHO is at the crank.

Perhaps Bob was using the wrong oil. :lol: