Bypass rubber hooks

"1992 Volvo230/SP sterndrive -

"1992 Volvo230/SP sterndrive - exhaust and raw water discharge thru the lower unit AND raw water also discharges thru two rubber ports, one either side, at the bottom of the transom sterndrive mount. These ports, bent tubes with 'puckered' closures need to be replaced and I haven't been able to figure out how to do this. Picture attached. Any help would be appreciated.

"

"You are going to have some fu

"You are going to have some fun with this one. To replace those hoses you need to disconnect the Y-pipe from the transom shield by loosening the 4 screws (part 2), then remove the two hoses and install new ones.

http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&grou p=3119&GroupList=3136,3137,3134,3131,3139,3138,3129,3119,3126,3118,3120,3121,314 2,3123,3124,3114,3125,3116,3115,3128,3111,3112,3117,3122,3113

However, if you are lucky, you should be able to just loosen the above 4 screws about 3/8", slide the Y-pipe forward, then pull the bypass hoses from the outside, coat the flanges on the new ones with Perfect Seal or similar, then slide them in from the outside (turn them about 120º up and down to make sure the rubber flanges are in the transom shield groove), then position them properly and tighten again the 4 screws. The problem with this last method is that you will not know for sure that the hoses and o-ring around the Y-pipe are intact and in the right position.

Please note, the above should work on a 280, but I have never tried it on a SP. I'm not even sure you can reach the 4 screws without first removing the engine and the bellhousing. On the 280, the screws holding the Y-pipe are on the outdrive side of the transom shield.

If I was in your shoes, I would leave those hoses alone until the moment you have to pull the engine or the Y-pipe for a good reason. If the hoses are badly cracked, just try to patch them somehow from the outside."

"It's rather simple:
Remo

"It's rather simple:
Remove the drive, lift out the engine including intermediate housing, take out the exhaust Y-pipe and You can change the rubber hoses for exhaust by-pass! Then it is just to put it all back again!
Why do You want to change them?"

"I wouldn't even think of

"I wouldn't even think of changing those out!! What for, all they do dump a little water out so it doesn't have to go thru the drive. Who cares if they're cracked or worn or if they're even there at all."

"Boat Doc, I would not uderest

"Boat Doc, I would not uderestimate the importance of the bypass relief hoses. For starters, they need to be in reasonably good shape to prevent water from ingressing the exhaust when running on reverse. Also, I believe their mission is far more important than just throwing water and preventing exhaust back pressure while the engine is idling. If you look at the design of the 270 and 280 transom shields and exhaust systems until the late 70s, they allowed for a single bypass hole. That hole was plugged for 4 and 6 cylinder engines, but was provided with a relief hose for V-8s AQ190 and AQ240 (both Fords) and some of the early Chevys. Then, all of a sudden, the 280 transom shields were re-engineered in the late 70s or early 80s and came provided with a double bypass (two hoses), as well as the new type of bolt for the steering helmet and a shorter steering arm which was provided with a mechanical advantage system. To me, all those modifications were made to run V-8 engines above 200 HP. With higher powers, the steering helmet bolt obviously needed to be beefed-up, and the steering system needed to be re-designed to make it compatible with power steering and higher steering torque loads. Also, if you keep in mind that the internal diameter of the exhaust Y-pipe is 2-3/4" and the size of the relief holes is 1", the addition of the two relief holes increased the exhaust capacity by 25%, which allowed the 280 outdrives to run up to 300 HP engines without running into exhaust back-pressure problems that would restrict engine's performance. In fact, when the 290s were introduced, they came without double bypass, but I noticed that the diameter of the exhaust pipe is significantly larger.

Again, I have no literature about this, and the above are just my own conclusions when trying to understand VP's rationale for the changes in the 280 transom shield design. I would definitely value Morten Ringvold's opinion here, as he worked at the VP R&D section for some time.

Interestingly enough, you cannot fit a Y-pipe with single bypass on a 280 transom shield with double bypass (or vice versa) because the relief holes are lower on the double-bypass transom shield and Y-pipe than on the single-bypass version."

"Thanks for the advice gentlem

"Thanks for the advice gentlemen. I think that, for starters, I'll take El Pescador's advice and try some self-vulcanizing tape together with a little Marine Goo to patch them up and see how they hold together.

Thanks again!

What a great forum!!! I'll make sure that my 150 member fishing association is aware of it."

"The bypass holes /hoses and t

"The bypass holes /hoses and their design have multiple reasons.
To reduce back-pressure particularly when starting (crancking speed). The quadra-jet and 4 barrels might be a bit difficult at low rpm.
At higher revs and bigger engines the exhaust system is simply not 'big' enough, You need the extra area given by the relief hoses. But watch out if they gets dammaged: the engine might suck water back-wards as they are located between the engine and drive flapper.(No bellow flapper on V8 - only at the drive!)Note that the same set-up is used by the D40 diesel. At full throtle running V8 and D40 temperature was a problem. The drive simply got too hot without. Bushings were melting, seals burned, oil temp too high.
tecnically the best thing is to run the exhaust through transom, both for power and for drive temp, but a bit more complicated. However picking up 10% power encrease is not a big problem by doing it properly. You loose a lot by going through the drive!"

"Thank you for the information

"Thank you for the information, Morten. It seems I was right in my assumptions. Did not know the issue with the diesels and hight exhaust temperatures, though. I assume that larger cooling pumps would not have solved the problem as too much raw water would also restrict the exhaust.

I agree that, technically speaking, through-hull exhaust is best, but I also think that through drive exhaust is a fair trade-off for not having to carry ear muffs!!!"