Converting to thru hull exhaust

hello all. i'm considering

hello all. i'm considering going to a thru hull exhaust on my 1975 searay. it currently has a 888 mercruiser with the y- pipe to outdrive. i have end riser log style manifolds and was thinking of changing the risers to 15 degree and routing the exhaust thru transom. has anyone done this? i don't want to spend 2 grand on a custom stainless setup. i also found a center riser cast iron manifold setup that fits ford 302/351 engines that might work as well. the problem with the center riser manifold setup is that it only has one water hookup as oposed to the three i currently have. any help would be appreciated.

"Rob,

Just a couple things

"Rob,

Just a couple things to consider, You will need to replace the Y pipe with a block-off plate. This may require R&R of the engine. I'm not sure that part is still available from Mercruiser so you may need to fabricate one yourself.

You also will want to be sure you have the height to insure water will not enter the engine through the exhaust, this may require a riser or flappers.

The center riser manifolds are the best bet if you can get them plumbed.

Good luck,
Rick"

"hello rick. thanks for the re

"hello rick. thanks for the reply. i found the y-pipe block off plate on evilbay. i will have to remove the engine but that does not bother me as i have done it before and have the means to do it again. it looks like the osco/indmar manifolds will work the best as they have threaded plumbing holes that i can thread in different angled hose fittings as opposed to casted on hose fittings that are set in place.

i will have the thru hull fittings close to the top of my freeboard. the boat is a 1975 searay 18 foot so the exhaust would be about 16 iches above the waterline. is this enough space? i plan on using ruber exhaust flappers to avoid transome backsplash into the exhaust. will this be sufficient?

thanks again for the help, rob"

"Seems to me to be a "soun

"Seems to me to be a "sound" plan. Just keep in mind when changing manifolds, there may be some bracket work required to get all your control stuff remounted."