Mercruiser 8.1L Horizon risers and elbows

[ViperRy]

Would anyone here know if the elbows on top of the 6" risers on Mercruiser 8.1L Horizon motors are the "standard" height or 2" ? This would be on a 3700 SY. I won't have the boat in front of me for another week, any help would be greatly appreciated.

[rodrigo]

try getting the serial number and call your local mercury dealer.

[pascavone]

just call your local boat supply store, and most have them in stock.

it is unwise to just replace elbows, with out risers and manifolds.

the Osco's after market parts are as good as mercruizer.

[rodrigo]

iF your engines are Horizon's the risers are coolant cooled with your manifolds, the only thing thats in contact with salt water is elbow, the gasket between the riser and the elbow is closed. I wouldnt replace the riser. I did mine last year!

[ViperRy]

rodrigo: Even with the serial number, two available elbows are shown... a standard and a 2"

pascavone: I never said I wasn't replacing then manis and the risers. I had a simple question about elbows.

rodrigo: I believe you are incorrect. raw water runs through the water jackets not coolant in the 8.1s.

[rodrigo]

yep sorry. on mine there is no raw water in the riser just the elbow, I replaced them last year. I thought you were looking to replace them, I guess it depends the way your exhaust system angle down. good luck. here is a good link to get info on your boat http://www.maxumcustomercare.com/catalogs_index.html

[Nehalennia]

Originally Posted by pascavone

just call your local boat supply store, and most have them in stock.

it is unwise to just replace elbows, with out risers and manifolds.

the Osco's after market parts are as good as mercruizer.

First of all, that's not true. Second of all OSCO doesn't make manifolds for the 8.1L.

Stick with OEM. I replaced my complete exhaust spring '12 and was quoted prices from www.mercexhaust.com
I then took those prices to my local dealer that was going to do the work and said "If you can match these prices, I'd rather pay you to do the whole thing" they did, + I upgraded to the dryjoint style (not sure if they're applicable to the 8.1).

I hope that helps.

[ViperRy]

Originally Posted by Nehalennia

First of all, that's not true. Second of all OSCO doesn't make manifolds for the 8.1L.

Stick with OEM. I replaced my complete exhaust spring '12 and was quoted prices from www.mercexhaust.com
I then took those prices to my local dealer that was going to do the work and said "If you can match these prices, I'd rather pay you to do the whole thing" they did, + I upgraded to the dryjoint style (not sure if they're applicable to the 8.1).

I hope that helps.

Thanks for chiming in Nahelennia. I got a killer deal from Phil at Michigan Motorz on OEM manis, risers, and gaskets and it was at my door within 2 days. I haven't seen dry joints for the big block 8.1 or it would have been the go-to option.

I really just had a simple questions regarding the elbows but this thread got side tracked with a lot of 2 cents. It doesn't matter, everything went well and I will actually see the boat tomorrow so I can check the elbows currently installed myself. Just an FYI for anyone else, the only way you will know if you have the standard or the 2" rise elbows is if you visually check yourself because the 8.1 S/N will pop up both parts #s. This is why I hoped another 3700 SY owner would chime in.

[pascavone]

is not the 8.1 the same big block as a 7.4 just bored over?

[mmwjr]

Bored and stroked. I also think GM changed the angle of the exhaust ports.

[Nehalennia]

Originally Posted by pascavone

is not the 8.1 the same big block as a 7.4 just bored over?

Originally Posted by mmwjr

Bored and stroked. I also think GM changed the angle of the exhaust ports.

Kinda, completely different heads (including exhaust ports), intake and bolt pattern.

[pascavone]

dose anyone believe a 6.2 is equal to a 7.4?

or that the 8.1 would show and improvements in the water other then fuel consumption?

since he got his riser question answered, what a dry seal look like?

[mmwjr]

6.2 is small block that puts out about the same HP as the 7.4, not sure about the torque. The 6.2 is also lighter so HP to weight ratio is better.

IMO a small engine that work hard to be equal to a big block will have a shorter life.

I think you are refering to dry joint, looks like the old style you know but no water passages present at interface. Instead a tube that has a slip joint and runs parrallel cmplete the water flow from manifold to elbow. It's a short run few inches.

Here's a youtube on it

http://www.youtube.com/watch?v=E3KN8IIh4Fw

[pascavone]

i looked at the dry type joint setup, and it makes sense to change over to them, to avoid water in the engine, but i dont see a listing for them on a 7.4

[mmwjr]

I believe that merc had dropped the 7.4 and was using the 8.1 when they came out with the dry joint system. With the 8.1 having redesigned heads I don't know if the manifolds will bolt to a 7.4.