Osco manifolds junk ??? Leaking ??

[srpachanga22]

I have a 454 Mag engine, completely rebuilt with 10 hours. New "Osco" manifolds and risers (4"). The last time I had my boat out, I noticed water dripping from between manifold and head on both sides of engine. Checked my oil, Looked OK on dipstick, but when drained, slightly brown. (@#$!). Pulled risers and found water in manifolds. Riser to manifold gasket did not appear to be leaking, and bolts were tight when I removed it. What is everbody's opinion ?? Leaky riser gasket, defective riser, JUNK manifolds and risers ??? These "Osco" parts were brand new, out of the box.<br /><br />PS - The riser gaskets were not the silver/metal OE type. They were made from a paper/asbestos material. I used NO sealer on the gaskets during installation.

 

[Buttanic]

Re: Osco manifolds junk ??? Leaking ??

I had an after market riser that had two holes in the casting on the upstream side that let water run back into the manifold. I don't remember what brand it was but it cost me an engine rebuild because I didn't catch it soon enough. I would pull them off and look them over inside real good.<br /><br />Captain

 

[JasonB]

Re: Osco manifolds junk ??? Leaking ??

I have a set of Oscos on my V8 with about 30 hours so far and have no complaints.

 

[Ralph 123]

Re: Osco manifolds junk ??? Leaking ??

I have a set on one of my 350s and Aqua Power on the other. This is the second season for both and so far so good.<br /><br />When I bought the Oscos I got it from a place here just outside of Boston that really just works on cooling systems for very large ships like freighters and such. I remember they pulled out the gaskets that come with the Osco manifolds and/or risers and gave me "special" ones that the have specially stamped from some sort of asbestos.<br /><br />This may indicate a known issue whith the gaskets that come with the Oscos. I'd get a better one and give it a try before the end of the season.

 

[Jdeagro]

Re: Osco manifolds junk ??? Leaking ??

I know the people at Osco and I suggest you contact them for advice.

 

[crazy charlie]

Re: Osco manifolds junk ??? Leaking ??

I replaced my man and risers with Osco in the spring,used the osco gaskets.The motor is 5.0 lx mercr. no problems at all entire season.Charlie

 

[johnkc]

Re: Osco manifolds junk ??? Leaking ??

12 years and 800 hrs on osco manifolds on a 350 mercruiser no problems

 

[mabbott]

Re: Osco manifolds junk ??? Leaking ??

Do you have RWC or FWC? Did you have stainless steel block off plate between the manifold and riser with gaskets on both sides? Did you use Permatex Ultra Black gasket sealer? If you use the gasket sealer you shouldn't have a problem.

 

[Capt Ken]

Re: Osco manifolds junk ??? Leaking ??

Didja remove the paint from the mating surfaces of the manifold and riser? They paint those things to reduce corrosion during storage and the paint is uneven and may even have runs. Failure to remove the paint will result in leakage.

 

[srpachanga22]

Re: Osco manifolds junk ??? Leaking ??

I did remove the paint from the surfaces, and it is raw water cooled. I used no sealer, and no block off plate, just a gasket that has two slots and two restricter holes. <br />I am going to call Osco tomorrow to get their opinion.<br />I will post back when I solve this problem....

 

[yoced]

Re: Osco manifolds junk ??? Leaking ??

It is unlikely that the cause of your water problem is from defective parts when it shows up on both sides of an engine at the same time. Not to say impossible, but the odds are slim. When two sides fail at the same time it is almost always a systemic or installation problem.<br /> Most common cause of water in 454s is valve overlap sucking water into the engine - this is especially true of a newly rebuilt (RV cams anyone?) engine.<br /> Another possibility - how was the paint removed from the machined surfaces? Use of rotary discs will most often cause gasket leaks due to rounded surfaces, and some folks do a bang up job with files as well.<br /> You said your bolts still felt tight - is it possible that the bolts are bottomed out, but not tight on the riser?<br /> I would take a closer look at that gasket and the surfaces near it. If you can see rust streaks on the outside of the manifold at the gasket, or running across the gasket surface, then you can be almost certain that your gasket is also leaking into the interior.<br /><br />Sorry for going on so long.<br />-yoced