Exhaust Mainifold Question

LiveBait · 07-17-2009, 03:09 PM

The manifolds on my 351 Windsor are causing the engine to feel with water on all cylinders. What are my options in getting some manifolds. Original engine was a 1990 351 Windsor built by Redline. It is for a 21 foot Alumaweld jet boat. AT 309 pump if that matters. Thanks...

LiveBait · 07-17-2009, 06:07 PM

Thanks Riverhawk for the information. Another question, what is the difference in brands when it comes to exhaust manifolds. I have found manifolds made by Barr, GLM, OSCO, Sierra, etc. Seems some are way more expensive then others? Any performance or longevity between them. How about aluminum versus cast iron. Thanks in advance for anyones input.

baitsauce · 07-17-2009, 07:18 PM

Unless your'e building a race boat with a motor that isn't designed for long life stay away from aluminum. Cast iron is much more resiliant and won't warp as easily.

You may want to check to see why your's are leaking in the first place. If one or both are cracked it may be cost effective to have them welded up at a competant shop.

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LiveBait · 07-17-2009, 09:22 PM

When you look at them they look to be in good condition. I had a shop check them under pressure and they found one that had a major leak and the other one a minor leak. What are thoughts about longevity of these if they are repaired? If that is a good option does anyone know of a good repair place. My trailer is currently at Wensens Fabrication (the Fab Shop) having work done on it since my axle was damaged on my trip to Portland. My boat, trailer, and manifolds are all currently in Portland. Thanks...

baitsauce · 07-17-2009, 10:09 PM

You need to know what caused the crack in the first place? Overheating? Thermal shock? That is was it cooled very fast when it was hot? Such as spraying water on it when the engine and/or manifold(s) were warm?

There are some different schools of thought regarding cracks and crack repairs. Cast iron (or even aluminum) takes some special manufacturing techniques. For example, once a mold is poured it needs to be cooled very slowly. The slower the better. Otherwise internal stresses become trapped.

There are those who feel if a piece is cracked then it's a defect in manufacturing and should be tossed. Especially if it cracked for no apparant reason. That's why I asked what is the reason for the crack. The root cause? They feel if it cracked for no apparant reason then it must have been a manufacturing defect and even if it were repaired it will crack again.

However, others feel (including me) a crack is repaired correctly it will be better than new because the internal stresses that normally occurr in nearly any cast metal have been "relaxed" and is much less likely to occur again.

I won't get into the technical side of how to repair this, as any competant shop is able to repair it. But it is worth a try to have it repaired. If it breaks again then you are only out the cost of the repair and you'll end up with new manifold(s). However, if the repair is done correctly and it holds then your'e money ahead.

So bottom line....I'd repair it, install it, and run it!

Hope this is helps and this advice is worth exactly what you paid for it.

LiveBait · 07-18-2009, 09:27 PM

Hi Baitsauce,

Thanks for your advice. Still not sure what I am going to do. The manifolds are probably almost 20 year old. Maybe they are leaking into the exhaust due to corrosion. I know I have filled two motors fool of water because of them and don't want to take a chance in hydolocking and ruining another motor. The boat is getting a new rebuilt 351 Marine engine. Money is tight right now since I paid for the rebuilt engine and then last week I blew a head gasket on my truck, ruined the axle on my boat trailer, and now am looking to have these exhaust manifolds replaced/fixed. I did find a complete set of after market ones on ebay for $338 plus shipping. On Monday I am going to call the seller and find out if those come with any warranty. I talked to a local Portland business, very nice and competant, but they want over $600 for a set. Thanks for any input in advance.

namu mac · 07-19-2009, 06:48 PM

Has the boat seen a lot of salt water? That can cause a failure, especialy after 20 some years. I got new manifolds from Redline in Leweston a few years ago. Are the still in business?

LiveBait · 07-19-2009, 07:15 PM

From what I have heard Redline is no longer in business. The boat has seen its fair share of salt water from the looks of it.

baitsauce · 07-19-2009, 07:41 PM

LiveBait, that really sucks......

When I did my write-up I assumed they were cracked. Sorry. You know what "assume" means. If they are corroded then that changes things a lot. If the reason for the failure is corrosion then by all means change them out!!! Especially if they want $600.00 to repair.

Remember a boat is a hole in the water in which you throw money.....

Good luck and keep us posted.

nunyet · 07-21-2009, 02:58 PM

Are you sure the motor is not running backwards on shut down. A gas motor that will diesel on shut down will pump the engine full of water, seen this happen quite often.

nunyet

namu mac · 07-22-2009, 04:49 PM

If they are the same configuration then $600. is a good price and they are easy to replace.

Redhawk · 10-15-2009, 09:50 PM

Bait sauce. who could "weld" a cracked cast exhaust manifold that can't be purchase because it's too old? Could you pm me ?

baitsauce · 10-16-2009, 06:26 PM

Quote:

Originally Posted by Redhawk

Bait sauce. who could "weld" a cracked cast exhaust manifold that can't be purchase because it's too old? Could you pm me ?

PM sent.........