Vent installation on a 911

[Michael Snow]

I have my two fittings. On the 2002 on the floor, the bottom fitting was plastic (as was the top). Any reason why plastic won't work properly and as well? Also, if anyone's ever actually DONE this, any tips, tricks, or suggestions? What size hole saw do I need? The fittings are 1 1/2" ID (same as the 2002 I looked at), is that a 2" hole saw? You don't know how much I don't want to drill a 2" hole in my boat. For those in parts/service, I got the white (lower end) fitting from the marine dept (floor). But the black one I got from Tracker parts (bps) and is a bit longer. Black is the better color for the top one (red boat) and white seems to go with the tan bottom better. Besides, (broken record) that's what the 2002 on the floor had.

 

[Staci Matheis]

Mike -



Inside diameter of a fitting has absolutely no correlation to the outside diameter; you're going to have to measure it.



However..... Considering the very basic nature of the question you just asked..... I would.....



STRONGLY RECOMMEND THAT YOU NOT DO THIS YOURSELF.

PAY A PROFESSIONAL TO DO IT.



Please!



me

 

[Michael Snow]

OUCH... man, that hurt. The inside diameter does have correlation to the outside diameter. I'm guaranteed that the outside diameter is at least 1 1/2" . These are very generic fittings and I thought someone at BPS might already know this that has used these same parts before. But still, OUCH...

 

[Tony Payne]

Stupid question...



What is this vent you are installing and what does it do?

 

[Marke Cicero]

Mike,



If you are "replacing" a fitting, isn't the hole already there from the existing fitting?? If you can measure the ID then why don't you just measure the OD and determine what size hole you need to drill.



I also think what Scott was getting at is that 1 1/2" scedule 10 pipe will have a different OD than 1 1/2" schedule 40 or 80 pipe. The OD will change dramitcally as the wall thickness increases. So Scott's right. The only way to determin the OD is to measure it or determine what schedule pipe you have and then look it up.



Sim, your question is not stupid. I don't know what vent he's talking about either.



Mini has owned a few 911's maybe he'll chime in soon and offer some advice.



Marke

 

[Staci Matheis]

I believe the vent he's talking about is the one at the rear of the transom that relieves the suction so the 911 will get up on plane faster.



I'm sorry, Mike. I was kinda brutal. But all I really wanted to do was to keep you from doing anything to your boat that might damage it. I know that if I weren't absolutely sure about what I was doing - I wouldn't want to be cutting into the hull of a $30,000+ boat..... Bad enough that I screw up a 10-year old Diawa baitcaster!



O.D. is determined by the I.D. of a fitting, plus wall thickness and the threads..... And there is no single standard to any of them.....



me

 

[Michael Snow]

I had to see it for myself, so I'll explain. I THINK it's on all of the 9 series, and became standard in 2000, which was the "official" first year of the 9 series anyway. BUT, there are a number of 1999 models out there. I can only speak to the 911, but here goes. Where the remote oil fill is, maybe 2-4" below it will be a 1 1/2" ID (inside diameter) hole, just a normal thru-hull plastic fitting. It is attached to a hose that goes to another thru-hull fitting. The second fitting is on the bottom of the recessed area of the area rear of the pad. Yes, that doesn't sound very good... find your drain plug, WAY down there on the bottom. You have 4 or so wire mesh screens for filling livewells and such. Okay, there's a flat part parallel to the ground just behind there. If you don't have a nice 1 1/2" thru-hull fitting (i.e. HOLE), you don't have one.



WHY is there supposed to be one? It would seem that a vacuum forms there and makes the hole shot less than it could be. This vent relieves the vacuum, allowing a faster plane. I'm unsure of an impact on top-end, but I'm pretty sure there isn't a change there.



I'm doing the vent BEFORE I start dinking with hydrofoils. I've had too many people tell me that hydrofoils should be a last resort. Now, I'm not knocking the foils. They DO work, but there's a lot more pressure on the cavitation plate and thus the lower unit bolts than they were engineered to support.