Riser Extension Blocks - Full Closed Cooling ???

[tpenfield]

I guess because raising up the elbows with spacers slightly changes the angles of how the down pipes match up to the Y pipe....

I think the angle will be OK, as the 'down elbow' ends up being mostly vertical going into the Y-pipe.

My bad was not measuring the circumference correctly on the down elbow/Y-pipe . . . I used the coupler and took a rough measurement of 3.5", and figured it must be designed for such.

Now having the fit issue, I measured the down elbow more closely and got a circumference of 11.8", which then calculates to a diameter of 3.75"

The 3.5" diameter tube, having about an 11" circumference would need to stretch over 3/4" to fit . . . which it was not going to do.

I have 3.75" ID 'flex' tube on order, hopefully it gets here soon.

 

[tpenfield]

The 3-3/4” ID tube shipped today. So, I should be in good shape for the weekend to get the exhaust system completed.

 

[Lou C]

Sounds like it’s all coming together!

 

[tpenfield]

Quick Update. . .

The 3-3/4" ID exhaust tube is working out better, but . . .

Getting all the bits of the exhaust system to go together is proving the be quite challenging.

Ideally, you would assemble/fasten the exhaust pieces from the Y-pipe upward, placing the riser/elbow as the last step. However . . ., I've already installed the riser/elbows and did not want to do those over (would require new gaskets, etc.).

So, with that constraint, the 'best' technique that I have found is to 'slide' the 3-3/4" exhaust tube down the Y-pipe a couple more inches than it needs to be. Then mate the down/elbow to the riser/elbow and slide the exhaust tube back up the couple of inches. In theory all sounds good, except . . .

The shape of the Y-pipe becomes more square (in cross-section) than oval as it goes further down towards the transom assembly. So, sliding the exhaust tube down, then back up is quite difficult, because the exhaust tube, being stretched a bit due to the changing cross-section, has a death grip on the Y-pipe.

I'm going through a bit of Merc PowerTune to lube the tube & Y-pipe, even have used soap to 'grease' things, and tried baking the exhaust tube to get it hot right before assembly. Still a challenge. I worked on it all yesterday (Saturday) and got 1 engine done. 1 more to go . . .

The most difficult ones are on the 'inside' between the engines, since the access is more restricted. I'm a sucker for any ideas right now . . .

 

[alldodge]

I would be thinking that gaskets are cheaper then frustration and pain. New gasket and a cold beer sounds better

 

[Lou C]

Ok Ted I had the same issue with my OMC with the original one piece manifolds because the one piece design combined with the fact that OMC used long studs and nuts to retain the manifolds meant that the lower exhaust hoses had to be slid down first before the manifolds would slide off the studs. So how I did it was to get a hairdryer and a long thin screwdriver and silicone spray. I warmed up the lower hoses with the hairdryer and sprayed silicone on the lower part of the Y pipe. Then slid the thin screwdriver up between the lower hose and the Y pipe to break it free. Lastly slide the lower hoses as far down as they will go. Yep it’s a bit of a wrestling match. However I liked those manifolds because in approx 15 years they never leaked because there was no joint between the manifold and the elbow section and the use of plated studs and nuts (no corrosion) meant no broken off bolts in the head.

 

[tpenfield]

Update . . .

I finally pulled the riser/elbows on the starboard engine to finish the exhaust connections. All set . . .

Note to self: Always assemble the exhaust system from the Y-pipe upward