Suitability of fully synthetic oil in lieu of mineral for Bravo outdrive

[dave1dpc]

Having converted my outdrives to a direct water pick up I would like to use F/S 75w90 which should cope with the higher oil temperatures . With much higher output and competition drives this is recommended sometimes with a shower unit.

 

[aerobat]

Careful ... a buddy next to me has a sealine s34 with the rare mercruiser d.4.2 and bravo2 . thru hull pickup which he completely wrecked .

He cruised on plane for a very prolonged time until closing the throttles before harbour entry . At this moment one drive sized and virtually exploded .

The mechanic said that due to the thru hull pickup and being on plane for hours the drive got glowing hot but somehow made it until slow down . When he slowed down he ditched the a** into the sea , shock cooled the unit and produced a catastrophic damage on the drive .

That said i had no issues with sierra marine synthetic on a bravo3 on my previous boat

 

[spannerman]

When you have a direct intake it is IMPERATIVE that the hose from the drive to the transom has about 2 inches cut out of it as per workshop manual.This is to allow water to circulate through the drives cooling passages as it would when using the drive intake for cooling. Obviously the fitting on the inside of the transom is removed and the Mercruiser blanking plate fitted.

 

[jointventureII]

When you have a direct intake it is IMPERATIVE that the hose from the drive to the transom has about 2 inches cut out of it as per workshop manual.This is to allow water to circulate through the drives cooling passages as it would when using the drive intake for cooling. Obviously the fitting on the inside of the transom is removed and the Mercruiser blanking plate fitted.

Yeah that's how mine is - the outlet of that hose also sprays the water around a bit off, assisting cooling on the inside. I considered a drive shower but it seems like unless the boat is trailered, it'll just chock up with growth in no time.

I just use the recommended Quicksilver oils.

 

[MapisM]

I would like to use F/S 75w90

That's what I did with the Bravo XR of my last lake toy, but for different reasons, already explained in this old thread.

BTW, my boat wasn't exactly a speed demon, but not too shabby either, being capable of 72mph, and I would have never remotely considered a direct pickup conversion.
Ok, actually the XR had the so-called DWP (dual water pickup), with an intake also on the tip of the nose cone (to cope with semi-surface installation, with very high X-dimension).
But imho, if you enter the speed league which demands a direct pickup, I would question the Bravo outdrive as a whole.
Mind, I know that over the Pond folks pimp up engines mated to Bravo outdrives (often, not even XR), pushing the boat boundaries close to 3 digits speeds.
But personally, I'd rather have a boat that doesn't wreck the outdrive(s) almost as frequently as she needs a fuel refill...

PS: I just updated the thread linked above, re-posting the Photobucket pics which in the meantime got lost.
For showing the mess that the original Merc oil can make, they really are worth a thousand words!

 

[dave1dpc]

When you have a direct intake it is IMPERATIVE that the hose from the drive to the transom has about 2 inches cut out of it as per workshop manual.This is to allow water to circulate through the drives cooling passages as it would when using the drive intake for cooling. Obviously the fitting on the inside of the transom is removed and the Mercruiser blanking plate fitted.

When you have a direct intake it is IMPERATIVE that the hose from the drive to the transom has about 2 inches cut out of it as per workshop manual.This is to allow water to circulate through the drives cooling passages as it would when using the drive intake for cooling. Obviously the fitting on the inside of the transom is removed and the Mercruiser blanking plate fitted.

I have a bravo outdrive manual but can find no reference to these recommendations? Thanks for your input.

 

[Elessar]

Having converted my outdrives to a direct water pick up I would like to use F/S 75w90 which should cope with the higher oil temperatures . With much higher output and competition drives this is recommended sometimes with a shower unit.

Even though Mercruiser sell a blanking plate these drives need the cooling of the water flow through them.
I recommend a Y to draw water through your strainer and through the drive.
And get a drive shower too.
I blew one up after 100 miles on the plane and a rapid stop, plunging the drive into sea water.
The replacement was fine with the extra cooling.

 

[spannerman]

The blanking plate is on the inside of the transom of the transom so water doesn’t flood in when you remove the standard water inlet hose and switch to a direct intake. The drive will have water circulating through it when under way providing the hose from the drive to the transom is cut to allow the water to escape after passing through the drive.
This is specified by Mercruiser when using a direct intake.

 

[Elessar]

The blanking plate is on the inside of the transom of the transom so water doesn’t flood in when you remove the standard water inlet hose and switch to a direct intake. The drive will have water circulating through it when under way providing the hose from the drive to the transom is cut to allow the water to escape after passing through the drive.
This is specified by Mercruiser when using a direct intake.

Yes it does specify that and you know Mercruiser stuff more than just about anyone. I still think that’s a bit of a bodge and prefer my Y inlet solution. But what you say is essential if you don’t do the Y.
My drive that blew up had not had the pipe cut.

 

[dave1dpc]

The blanking plate is on the inside of the transom of the transom so water doesn’t flood in when you remove the standard water inlet hose and switch to a direct intake. The drive will have water circulating through it when under way providing the hose from the drive to the transom is cut to allow the water to escape after passing through the drive.
This is specified by Mercruiser when using a direct intake.

Yes thanks for that. I have already blanked off the inside outlet. It was only that i could not see any reference in the bravo manual regards converting to hull intake or trunchating the water hose.