I dragged my installation manual out of the shop to check the requirements. The manual is for Mercruiser gasoline sterndrive models and includes the 350 Mag MPI in both Alpha and Bravo configurations with Serial number OM668000 and above. Do yourself a favor and throw out that Seloc manual and get the factory service manual. You'll need two manuals, one for engine, one for Bravo drive.

Anyway, the installation manual says the minimum exhaust elbow height is 13" (33.0 cm) above the static waterline with the boat fully loaded. That means full tankage, gear and crew. My fully loaded static waterline is around the middle of the scuppers unless everyone moves to the back of the boat. That puts it an inch or two below the deck. Which would make minimum elbow height around 11 or 12 inches above the deck to the top surface of the elbow casting. I just checked mine and it's at 11 3/4".

If you increase your exhaust elbow height, in addition to the riser extensions, you'll need longer intermediate elbows. Those are the ones that connect the riser elbow to the Y pipe. They will have a slightly sharper angle than the shorter ones.

Something else you might want to check:

From page 19 of the installation manual - IMPORTANT: Bravo closed cooled models require a through the hull or through the transom pickup in addition to the sterndrive water inlets in order to meet the minimum flow specifications.

So there should be a Y fitting on the engine cooling hose behind the seawater pump on the starbord side of the engine. The Y fitting should have one hose fed from the Bravo transom assembly, and another fed from a through hull.

Dave

This is a good thread, a lot of key information. Not enough height and we may be costing ourselves needless manifolds and risers, not to mention possible (likely) engine damage of not having sufficient height!

Thank you! Please continue.

Don`t chop the throttle and let them idle for 2 minnows before shutdown.

More on the topic:

http://www.perfprotech.com/blog/unca...d-and-checking

Dave

This is all great stuff.

Mine does have a thru hull pickup and a Y pipe to the gimbal/lower unit for raw sea water pickup. I was confused by that, now it makes sense.

I bet my exhaust risers are not much above the deck, judging by the pics. the scum line on the boat is perhaps 4-5" below the scuppers, so fully loaded, I can see the waterline being close to the scuppers.

I do have a post 2002 engine, , and 0W0..... serial number- so with the dry joint, all the riser extension kits are >$400 that I can find. I looked at eBasic Power, Osco, Mercury... Unless I am dong something wrong?

The older extensions are 1/2-1/3 the price. If I need the expensive dry joint extensions, I need them. But it looks like a lot of $$$ for a few bolts, gaskets and lumps of cast iron. Plus, as you pointed out, the intermediate elbows.

I will take measurements and see how far off it is. Is there a known downside to more than 13" above waterline? Because the pricing for a 3" extension and 6" is about identical. So I might wind up with 15". I guess if 13" is the minimum, then a bit more is OK.

Pictures of the (scum) waterline before the repower. Blue Heron passed these along.

And a few more. I did pick up scraps of the canvas, but not all of it, and almost no electronics. And an awful lot of thru-hulls. Mostly plastic, it looks.

Two more. I hope this trim tab placement is right- a bit inboard. Again, thanks to Blue heron, and these pics are 11 ish years old.

Here a few more. Looks like someone did not like the name at some point. You can see where they took off the lettering in the last pic. I have a couple shots of the old engine as well.

strick

That's a funny way to attach an outdrive... :eek:

There was rumor that it was used as a rockfinder once.