Risers, Manifolds, Oil and Water/Fuel Separators 5.7 Merc

[luvmystang67]

Okay, so I've had inboards before and am a fairly competent shade tree mechanic.  We just picked up a 1989 Sea Ray with a 5.7 Merc (350 chev) in it.  It has freshwater cooling. 

1) Oil change: Does everyone use the vacuum pumps through the dipsticks?  Have people had good luck with this?  Do you do it any more often than once a season?

2) Risers/Manifolds:  I don't think the risers have been changed since the engine was new in 2009.  I believe it has about 300 hours on it since that time.  The risers still stay relatively cool and I believe are functioning just fine.  No visible rust on the outside of the risers that would indicate problems inside.  It has been used mostly in salt.  Should I just pull of the risers, inspect and clean them, change the gaskets and reassemble or do I need to replace the risers?  Or do I only need to replace the risers if they look bad?  Also, I would assume the manifolds are good for longer and don't plan on replacing them since they're on the fresh water system.  Any thoughts here?

3) It has an oil filter style water/fuel separator... any idea on the change interval on those?  Looks like it was last changed in 2012 and there's probably 100 hours since then.

4) Is a gasket all that keeps the raw water from entering the manifolds and the exhaust at the bottom of the riser?

Thanks,
Stang

[Fastass350]

Used to work on lots of mercs, but been a while so bear with me If you feel the risers and they are cool all is usually good. Can't hurt to pull them and clean the outer water passages, sometimes they rust up. Otherwise if they stay cool to the touch and you don't have water in the oil you should be good. If you pull them, or even if you don't, check the exhaust baffles. If they are originals I'd upgrade to the new style they last longer. They are below the boot that connects the riser and elbow to the exhaust Y, that goes down through the transom.  When in place and working good they keep water from backflushing into the engine if you stop fast or take a wave up the rear. Of the boat.   

I'd change the water seperator every 6 months if it was me. And yes oil changes through the dipstick via vacuum. Or install a drain hose that connects with a clip to transom drain plug, then you pull it out and drain it.   
Raw water (lake water) runs through the exhaust. A gasket between the riser and manifold is all that keeps coolant and raw water from mixing. Depending on the system, there's full, 3/4 and maybe even 1/2 systems. Some just cool the block and heads, some manifolds too, etc...

Hope any of that made sense. PM me for any help I'm very familiar with them and still have a bunch of specialty tools.

Chris

[luvmystang67]

Thanks for the response.

The risers are warm to the touch, but certainly not hot.  When you say cool, you don't mean cold right?  Like they can be 70-90 degrees and its still okay I'm assuming?  Other functioning risers I've felt in the past seem to be around there.

I was thinking about checking them and replacing at least the gasket.  They've had salt water run through them for years.  I think I'm going to use a pump for the oil.  I'll check on the baffles, that makes sense and I've never given those a lot of consideration.

[huntnphool]

Pics of the risers?

[Fastass350]

Yes just cool to the touch. If you can't keep your hands on them then they are too hot.

Chris