Exhaust manifold water hose routing?

CZSteve · Jul 3, 2005

Finally getting down-n-dirty; here's the beginning of many questions.

I have a '77 Sea Ray (SRV197) we put a new block in and I'm replacing the previous log manifolds w/ Osco/Barr center risers. The instructions that came w/ the manifolds were sparse. Apparently they're are different options for the water hoses. http://www.perfprotech.com/Home/Techtips/marine exhaust manifolds.htm I'm debating between the 1 hose & 2 hose options. Here's a pic of the dry fit of my setup.

Any advantage of 1 vs. 2 hoses? The manifolds have inlets fore & aft, both appear to be level. The front inlet would be easier to plumb, but the rear would be lower when under way w/ the bow up. Does it matter what inlet I use? I thought about running the hose from the thermostat housing to the front inlet of the manifold and also to the riser via a 'T' fitting in the water hose coming off the thermostat housing. Thoughts? Sorry for the long post.

Haut Medoc · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Hard to tell exactly what were looking at here...What year and model...Some more pics of exactly where the inlets are and a good shot of the t-stat housing would be helpful. However if you had log style before didn't they have front and back inlets? Did it have one inlet for each riser. Sounds like you have the same amount of inlets. I think I would plumb it like it was before.....J

CZSteve · Jul 3, 2005

Re: Exhaust manifold water hose routing?

J., Thanks for responding. I imagine most people are out on the lake enjoying the holiday weekend. Strange, but I actually enjoy this tinkering stage. Here are some more pics, along w/ the instrucs. The boat is a '77 Sea Ray w/ an Alpha 1. These manifolds are aftermarket, along w/ the new thermostat housing. The original posts also has the online reference for routing options.

1st: shows the inlet on the front of the manifold & the riser. 2nd: shows the rear inlet on the manifold.

Haut Medoc · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Well, I'm still trying to rally after last night. You still didn't say what the engine is, but it sure looks like a small block Chevy. What is its' H.P. rating? My guess is that your old t-stat housing had more water outlets. The one that I see from your new set looks like you could only go with the one hose option (unless I'm missing something). If you use the old assembly, middle two to the risers, top two to the manifoldS. I think I would mount on the back of the manifolds, (one or two hose configuration). The stock Merc. ones have the inlet bottom center, I don't know why Osco doesn't do that.........J

CZSteve · Jul 3, 2005

Re: Exhaust manifold water hose routing?

J, Yes, it's a SB Chevy (355ci). You problably don't want to know the HP... according to the dyno software, it's around 360 HP. I've already de-tuned it some via gasket changes by dropping the compression to about 9.5:1. Plan on changing the cam, but waiting to get it fired up first to see how the idle is. My biggest concern is damage to outdrive w/ too much power/torque. Boat was originally equipped w/ a 305ci rated @ 228 HP. Orig. block & exhaust was cracked from freezing. Picked up a solid boat, trailer, etc. for $800.00. Had the motor left over from a '71 Camaro I had built-up. (yes, I'm aware of what needs to be covered for converting to marine use) Back on topic: What's the advantage of having the water enter at two different points? IE: @ the exhaust manifold & @ the riser. If it is advantageous, why not spilt the hose coming off the outlet port of the thermostat via a brass 'T' fitting?

Haut Medoc · Jul 3, 2005

Re: Exhaust manifold water hose routing?

I guess it could work although they might work against each other. The difference is that with the old housing, water to the risers does not go through the thermostat, it goes right to the riser and makes them run cooler. 360 H.P.will kill an Alpha right quick if you are heavy handed with it. They are only rated too 300 H.P. Well, gotta roll, you will get more input I'm sure.......Take Care, Jeff

Scaaty · Jul 3, 2005

Re: Exhaust manifold water hose routing?

If you are simply raw water cooled (and that thermostat housing suggest it is), one hose (per side)......from the thermostat housing to the bottom on the mans. Plug the riser hole, and move the fitting to the mans bottom front. You only have two stat outlets, and have them go into the bottom of the man's,....cool water does its job transfering heat from around the exhaust ports, and out to the top through the riser and exhaust. Make sure you used the open gasket.

Scaaty · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Something like this...

Scaaty · Jul 3, 2005

Re: Exhaust manifold water hose routing?

That above pic is not my engine (off ebay I think), but I'm going to do something similar down the line. Anyway, thats how you should route the water lines. By the way, I have Barr Mans now, that replaced the old style Volvo 350 Mans (exhaust out the back and almost straight down). Did you have any problem with something like adding more exhaust hose, to get to the "Y" pipe okay? I look like I would need to add way to much rubber hose to attach, by then again, I don't know. The center rise exit at a different angle, and farther up. Know what I'm talking about? And also, what did you pay (and where did you find) that thermostat housing? Mine rusted through, and I found (very LUCKY) another on ebay. Thanks, Robby

Scaaty · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Originally posted by Robby6950: That above pic is not my engine (off ebay I think), but I'm going to do something similar down the line. Anyway, thats how you should route the water lines. By the way, I have Barr Mans now, that replaced the old style Volvo 350 Mans (exhaust out the back and almost straight down). Studying your last photo, did you have any problem with something like adding more exhaust hose, to get to the "Y" pipe okay? I look like I would need to add way to much rubber hose to attach, by then again, I don't know. The center rise exit at a different angle, and farther up. Know what I'm talking about? And also, what did you pay (and where did you find) that thermostat housing? Mine rusted through, and I found (very LUCKY) another on ebay. Thanks, Robby

CZSteve · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Alright, it's quittin' time.

Hope this floats:

Here's another shot of the frame I'm using to build my new engine cover / sun deck. The boat had been re-upholstered and they used a 'ton' of wood to build the cover/deck. It was VERY heavy and had to be lifted off via two people, difficult to get at the engine while under way. I had a frame of 2" square alum. tubing welded that's bolted w/ hinges to the aft. Sorry, I'm a little too proud of this.

Robby, The thermostat housing, elbows, and exhaust tubing all came as a kit designed to replace the log style mercruisers w/ the center riser. Here's the link: http://ebasicpower.american-data.net/Merchant2/merchant.mv?

CZSteve · Jul 3, 2005

Re: Exhaust manifold water hose routing?

Robby, Sorry, the link doesn't seem to take you directly to the kit I used. Type in part # "BPIMANMERCHV I-O" using their search function and it will take you there. The entire kit was $669.00

Scaaty · Jul 3, 2005

Re: Exhaust manifold water hose routing?

No prob on the link...I have a Ebasic catalog in front of me....thanks, and good luck with the boat!

Exhaust manifold water hose routing?

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