offshorexcursion

iTrader: (5)

Curious if a "standard" style sterndrive (like a Bravo XR, Imco SC, SCX, or BMAX etc) is harder on internal componets like gears, or would a surface drive (like a #6, M8, Indy, NXT etc.) be more strenuous on gears etc? Equal HP/Torque/boat.

Surface drives require a much more expensive prop. Normaly its larger in diamiter which explains some of the increase in price. The higher price might lead me to believe they are stronger. Leading me to believe a "surface style" drive is harder on internal componets and propellers or they would not need to be stronger. But these $5400 and up props still throw blades off like its their job!

Standard style sterndrives have a competely submerged prop which might seem like thats putting more pressure on internal componets compared to a surface piercing prop.

Any thoughts or better yet proof!

Philm

Surfacing a propeller is harder on it than keeping it fully submerged. Every rotation the blades are getting loaded and unloaded as they enter and leave the water. That is why sufacing bravo style props with big hp often leads to pitching off blade tips (I have thrown 2 of them myself in 3 years). The loading and unloading causes flex that a submerged drive doesnt usually see.

I have no clue if surfacing is harder on gearsets, i just assume that the gears are stronger in these drives because they are designed to be behind big HP.

offshorexcursion

iTrader: (5)

I agree with you on why the surface drive props are stronger and how the gears are normally stronger for higher horsepower applications.

Still courious which is tougher on gears etc.

47EXCALIBUR

its measured by lbs per sq inch of torque on the gear face...the more surface area of gears touching each other spread the load out....so bigger gears with multiple teeth meshing at the same time is alot stronger..so lets say 500hp/trq motors on 1sq/inch of gears per revolution....and 1075 hp/trq motors on 3sq/inch of gears per revolution,,,,equals the #6drives etc are alot stronger bc the gears see alot less load repectivly on the gears

BadReputation

Surfacing style props are harder on everything. Not only are they usually higher hp apps, but the loading and unloading of the surfacing blade causes a vibration as the blade "slaps" back into the water. Many people will complain about low speed vibrations with surfacing style drives.

Twin O/B Sonic

Agreed w/above on surfacing props and l/u's. Want to start breaking stuff, thats how you do it.

Good point's a friend made to me about this argumnet are that,
#1. If your boat requires much "up trim" and bow lift to run, surface drive won't work since the prop is out of the water.
#2. Around dock they suck. To prove this one to you ride in one of your friends fast O/B's where the motor is jacked to the moon. Watch when you come into dock. The motors have almost no effect.
In reverse they have none.
Surface drives are the same.
$3. If you ever swim off the back of your boat...., yikes.

47EXCALIBUR

i have surface drives on my boat and there better around the docks than the bravos that usd to be on it,,,,, an out board is a completely different animal especially if they are set high....a surface drive is set back away from the boat and is trimable up and down... the drive grabs all the water around the docks in the down position and is very responsive.....

Twin O/B Sonic

what my friends have told me about theirs. One of them has his on his shop floor.

Would think the effect of trim (lack of) would be tough to dispute.

Rik

Do you swim off the back of an outboard boat?

Twin O/B Sonic

time.

At rest, wheels are way under water and straight under motors and protected by the cavitation plates. Not on a stick 3' behind the boat.

Have also read what I wrote, many times by many different people.