uh oh... Mercruiser parts not the same!

[woodrat]

I am busy today pulling the engine out of my 72 bell boy (pre alpha mercruiser with chevy 2.5l) and changing out the whole outdrive assembly with parts and pieces collected from ebay and other places. Last summer I bought the inner transom plate and the outer transom assembly with the gimbal ring from a fellow not far way from me, assuming that they had come off the same craft.

Today, I finally got my broken pieces off and realized that they are not exactly the same as the "new" parts.

this is a picture of my old assembly where the exhaust downpipe goes through the transom.

this is the new part, with the inner plate that came with it. The ports pointed out by the arrows are what my old one did not have. Also, the new inner plate is just like my old one, but obviously not the one that goes with the new assembly on the outside.

and these little ports on the outside of the new part are also not on my old part. They go right into the exhaust tube.

these last holes don't look that important really, I can imagine getting away with using this part if that was the only difference. However, I am concerned about the other ports on the inside. What are they for? Is there any chance of just ignoring them, or am I back to searching for another part?

So far I have not found the answer in the mercruiser manuals...

 

[woodrat]

Re: uh oh... Mercruiser parts not the same!

I do have another parts boat here, but on that one, the hydraulic lines for the lift cylinders are plumbed totally differently...

 

[woodrat]

Re: uh oh... Mercruiser parts not the same!

I've poked around in there and looked the unit over carefully, and I just don't see where these holes go, unless it is a loop and they go to each other. And I don't see what that would do, if that is the case?

???

 

[Haut Medoc]

Re: uh oh... Mercruiser parts not the same!

Those holes are not connected?......
I would think that they are exhaust relief ports........
I think you are gonna need to get the right inner transom plate & the exhaust pipe that will fit it as well......
If you can find the casting # off of the new transom shield, I think it would help immensly with getting it right....
Are there two bolt holes that are being obscured by the plate in pic #2?..........
Hoping to see you down under weekend after next.......​

 

[woodrat]

Re: uh oh... Mercruiser parts not the same!

exhaust relief ports? I don't understand what they would do. As near as I can tell, they are just a loop, I can't see that they connect to anything. If they are just a loop, what would be the harm in just ignoring them?

If the exhaust pipe for that part is different, would the riser or manifold need to be different to match?

yes, there are two more bolt holes there...

 

[Haut Medoc]

Re: uh oh... Mercruiser parts not the same!

The arrows on the holes in pic #2 correspond to the holes at the arrows in pic#3, I'll wager.....
The new one you have has exhaust relief hole that help the engine breathe easier when sitting at idle.....
Otherwise all exhaust goes through the prop, like on the old model.....
The transom shield you have looks very much like it is from an 888....
The two bottom holes under the relief ports help hold the y pipe in place.....
You are gonna have to put the new transom shield in place & look at how those holes fit in relation to the transom cut out......
If they are not part of the cut out, then you may be able to block them off....
But if you can see them with the transom shield in place, you will need the inner plate & the proper exhaust pipe.....
Put it this way: if you do not block them off, you will have water coming in through there....
I am not sure if the shield for a v8 is compatible with the inner shield & exhaust pipe for a 4 cyl......
What is the part # casted on the new one.....
Someone posted about a place in Minn. that deals in old stuff, they may be helpful in determinig if it can be done....
I doubt whether you will need to get a new riser/man though, they should be the same.....​

 

[woodrat]

Re: uh oh... Mercruiser parts not the same!

Thanks for the advice; I am trying to get this at least part way back together this weekend. I finally found some online parts diagrams that show those extra holes on a v8 transom assembly, but not on anything else.

those ports in the last picture clearly go right into the main exhaust tube with the bellows. Nothing else intersects with them. As near as I can tell from looking, the extra ports are at best a loop, and they don't seem to connect to water anywhere.

But your point about fitting the transom hole is well-taken. I just went and looked and measured again and found that those extra ports are so low that they would not fit through my existing transom hole...

Now I guess it's time to take apart the assembly on the parts boat and see if I can make that one work. It is older than the one I have, but it may work if I can re route the tilt cylinder lines. Fortunately, I have a nice tight gimbal ring to use with whatever housing I can come up with. And now I have a V8 transom assembly to sell on ebay I guess.... i'm sure the guy I got it from didn't know the difference either, and I couldn't tell that mine was different until I pulled the engine.