Broke another drive over the weekend. Opinions please
 

Gutted the upper gear set in my SEI (alpha) drive over the weekend. This makes two drives in less than a year with very little run time.

Brief synopsis:
Boat is a 20ft Concord. Weighs about 2800 lbs or so
Mild built 350, Horsepower <= 400
Last summer I gutted my 1.50 ratio alpha one
Replaced it with a new SEI 1.65 ratio drive
Did correct break in procedure on new drive.
Was pulling the kids around on the tube and all was good early in the day.
We get to the swimming cove and the boat starts making a clunking noise in neutral
Tow boat in
Drain drive oil
Oil is black in color and full of metal flakes
Only third time out with boat this year
Any ideas why I'm killing gears all of a sudden?

What oil?
How often do you change it?

Mercury oil, changed every year at least

The new drive had the fluid changed at the beginning of the season
I've only ran a tank and a half of gas through the boat this season.

I should also mention that at WOT the engine is running at about 5600-5800 rpm. Most I hold it there is 30 seconds to a minute at a time

400 hp and 5800 rpm is asking a lot from an alpha......

I know I'm over the power limit. Would jumping from a 21p to a 23p prop help some by lowering the rpm?

You are in a heavy boat pushing too much tru it. Pulling skiers too.....

Run 140 weight and hope for the best.

Then you are just increasing the torque load on the drive. Its bravo shopping time

Once my warranty on the SEI drive runs out I'll probably start looking

I have a similar engine at about 375 horse in a 206 formula. SEI upper, stock merc lower alpha. I turn about 5600 with a 21 and 5200 with a 23 mirage. I haven't had any issues, though I am easy on planing off, no airing the prop out, and no slamming the throttle forward. Also I have never towed anyone for water sports which is probably really hard on the drive. I run amsoil synthetic lube.

Maybe you should drop down to a 17 pitch for the days you are doing watersports

Check with George at AADS, he has new improved parts for Bravo and Alpha that increase power handling. He also recommends Amsoil Extreme Gear oil, I run the 75W110 in my Bravo.

I beat the crap out of my 1.5 SEI 'Alpha'. Turn a 21" and a 23" to 5400rpm and change.

I will holeshot with the best of them....about 2800lb boat. Wife, small dog, and a very small cooler.

I use 3 blade cleavers because my boat like them for some reason. They slip more than more normal props.

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Blowing up Bravo's and Alpha's was a yearly ritual for me (different boats.)

Alpha's implode more from too high shifting rpm than anything else.

I will not go over 800rpm shift speed...ever again.

Lower than that is better...but 800rpm seems to live fine. Over that and Mr clunky clunky comes to visit.

That's my experience.

Note: This has been my only SEI as I haven't killed it. About 5 yrs old. It's first gear lube change at say 5-10hrs had basically no fuzz on the magnet. Mercruiser High Performance green gear oil. Drive shower. Never made much of a gear type whine noise like others say you get for first few hrs of SEI's.

Maybe I got lucky with a better one, I don't know. But when accelerating for speed, I don't go anyslower than a Micro second putting my throttle down thru the dash. LOL.

I like your style lol

I've broken a few shifters, fingers, and radio's going into 3rd. Think Chevelle, Camaro, and etc.

Few yrs ago, pulled a shifter out of a Honda going into 4th. It was a schit can with a fart can though. Ha !

Yeah, but do you pull the neighbors fat kid around in a tube??? He definitely needs to drop pitch to do that, its like trying to do second gear clutch dumps

I had a verticle gate hooked to an M22 in the old goat... bulletproof...

No. I don't. And that could be a difference.

Used to with stock motor + stock Merc Alpha which I still used the 21" for normal boating, but a 19" for skiing/tubing. The 19" was a POS aluminum that reved like a 17" should.

If I where still using the boat for watersports, I would be using that prop for that.

I have a shed full of props, and use all different ones a bunch...prop that goes on depends on what type of boating we'll be doing for the day..including weather conditions (think wave height) we will be facing. Seriously. These little lightweight boats respond (good or bad) to the littlest change in anything.

So 5700 shall we say how many times did the prop leave the water...get a little airbourne....just a small wake hop...At that load and rpm... Alpha... SEI..whatever, is well say good bye...

Just Saying.....:whistle:

I'm not into catching much air. I'll let the boat dance a little on small chop but I don't beat it's guts out when it's rough