When to replace manifolds and risers

[ldnjr]

Is there a general guideline on replacing manifolds and risers on a 310 Sundancer?

 

[ENstig8or]

In salt water, plan on 4 to 5 years.

 

[Boater420]

Something to consider...aftermarket parts generally don't last as long as OEM parts. When you replace them, if you go the aftermarket route, don't expect them to last as long.

 

[fwebster]

With Mercruiser parts, begin checking the risers after the 3rd year and count on replacing in the 5th year. Checking them is easy...just takes 2 gaskets. Pop them off the manifolds and look inside both the riser and manifold.

After market parts are cheaper.....for a reason. They don't last as long as OEM parts. Begin checking Barr, Osco, etc. castings after the first year and every year there after.

 

[JVM225]

Another vote for OEM stuff. The aftermarket stuff doesn’t hold up and the mounting surfaces are often not consistently flat. Frank’s advice for inspection and replacement intervals is spot on. You should get 5 years out of the E coated Mercruiser exhaust. Just be careful when inspecting because you can’t alway see a problem developing where the raw water side is going to leak in to the exhaust gas side so even if they still look good at 5 years you should replace them anyway. It was a fairly easy job on my old 300 so yours should be about the same if you have small blocks. I always replace all the bolts with new ones when I replace manifolds and risers.
Also, I wouldn’t waste time or money replacing just risers. If a riser looks bad just replace everything. If your 310 has the small block V8’s you’re in luck because that is about the sweet spot in complete kits that include gaskets and bolts. I usually see them advertised for about 600 bucks. Not a bad deal for a V8. It cost me almost that much for the kit for my kids 3.0 Mercruiser last Spring, and the big block stuff costs a lot more.

 

[scoflaw]

Heard Barr is top notch, another merc site says they produce the castings for Merc and others.

 

[JVM225]

Heard Barr is top notch, another merc site says they produce the castings for Merc and others.

Not worth the few bucks you might save. If they do make them for Merc (I don’t think they do, but anything is possible) they don’t make them to the same specs or quality control.

 

[scoflaw]

Not worth the few bucks you might save. If they do make them for Merc (I don’t think they do, but anything is possible) they don’t make them to the same specs or quality control.

So if your not sure, how can you be sure the quality is inferior ?

 

[rmlsll]

I put full closed cooling on my saltwater 240 sundeck / 5.0. I also flush every time I get back. Expect this setup to last a long time.

 

[fwebster]

Heard Barr is top notch, another merc site says they produce the castings for Merc and others.

You may have heard or read good things about Barr, but my experience doesn't bear that out:

I invested in Barr manifolds and risers for my 390EC because they were cheaper. I decided to check them after 18 months, fully expecting to see pristine interior cavities. Of the 4 risers, 3 were already rusted thru and leaking seawater into the manifolds. I figure I was days away from ruining one or both engines.

The real problem was that Barr wouldn't replace the parts, even though they were well within their warranty period. We had to send the parts back to Barr at our expense for them to examine. 10 weeks later we got a resolution.......a discount on new Barr parts which I refused then argued 2 more weeks over getting a credit issued for a peorated amount. Now, had I waited on Barr, their faulty parts would have cost us 3 months on the water in the summer when the kids were out of school.

When I saw the rusted interior cavities on the Barr risers, I ordered new Mercruiser manifolds and risers that day and we only lost the use of the boat for 4 days. That set of Mercruiser risers lasted 5 years. Perhaps for some minor exterior part I might use after market parts, but on a major component as critical as exhaust castings, I've learned all I needed to know about Barr.

 

[northern]

This summer we started to get white smoke form both engines at start up. We had replaced the risers with OMC parts in 2013 and after doing that no white smoke at start up. I assume the risers are crusted inside with deposits and when the engine is warming up the water evaporated. I will replace them this winter with OEM parts. The manifold does not see salt water, it is cooled with anti freeze.

 

[Irie308]

If just replacing the risers do you need to run the engine afterwards? Reason i ask is i'm planning to do this over the winter once the boat has been winterized. So if i replace the risers the engines wouldn't be fired up until the spring.

 

[boatman37]

Mine are still the originals from 1986 according to the PO (who bought it new). Boat was used in Lake Erie almost its whole life.

 

[CaptRonn]

Mine are still the originals from 1986 according to the PO (who bought it new). Boat was used in Lake Erie almost its whole life.

I removed the manifolds and risers from my 93 400EC in March. This boat spent it's entire life on the Great Lakes and the manifold/risers were original. After removing them they were in excellent condition.

 

[JVM225]

Heard Barr is top notch, another merc site says they produce the castings for Merc and others.

I’ve seen aftermarket stuff have shorter life spans over the years, many times resulting in hydro locked motors, and have also seen where the mating surfaces of brand new aftermarket manifolds have had to be filed flat in order for the gasket to seal to the head properly.
Honestly, I wouldn’t install anything but OEM manifolds and risers in a boat I owned. If I did it for a living I wouldn’t install them in a customers boat either. Not all that much more money for OEM in the scheme of things.
A lot of aftermarket stuff is cheap Chinese castings that were copied from other bad castings. Not sure if Barr has their stuff cast for them over there or not, but they are probably cheaper for a reason.
Some “Made in China” can be a good value in certain situations, but other “Made in China” stuff is inferior and my experience has been most cast, or other metal stuff, from there is junk with poor quality control.
Just had an experience with cheap Chinese stuff today on my 68 GTO. The car has power front drum brakes and one of the wheel cylinders started to leak. Got new ones from the local Auto Parts Store. They were made in China and the threads for the brake lines were wrong and the bleeders would have been wedged against the spindle making bleeding impossible if they were installed. Poor quality control. Went to another parts store and they had the same Chinese crap. Finally got the correct ones from a place that deals with Classic Car Parts. Stamped right on the castings of the good ones is “Made in USA”. They were triple the price, but they are correct.
Same is true with brake rotors. You can get cheap Chinese replacements anywhere, and they will be fine until it comes time to do another brake job. If you cut them and reinstall with new pads you will wind up with a pulsating pedal. The rotors don’t hold a resurface well because of the poor quality of the metal. Not like the old days when you could cut the rotors once or twice. Whenever I do brakes on one of the daily drivers in the household these days I just get new rotors and throw the old ones in the recycle bin.

 

[SteveRuss]

no need to start the engine. Just remember to check for leaks in the spring and re-torque them after a few hours use.

 

[sbw1]

I removed the manifolds and risers from my 93 400EC in March. This boat spent it's entire life on the Great Lakes and the manifold/risers were original. After removing them they were in excellent condition.

Really not an apt comparison. Great Lake boaters do not replace these parts as they last the life of the engine and do not require inspection. Salt water boats...big difference as these are wear items.

 

[CaptRonn]

Really not an apt comparison. Great Lake boaters do not replace these parts as they last the life of the engine and do not require inspection. Salt water boats...big difference as these are wear items.

No sh*t Sherlock! Since the OP didn't actually state what his boat use was (fresh or salt) or what kind of system he had (FWC or RWC) I made my statement which included my boat's type of use.

 

[JVM225]

If just replacing the risers do you need to run the engine afterwards? Reason i ask is i'm planning to do this over the winter once the boat has been winterized. So if i replace the risers the engines wouldn't be fired up until the spring.

Nah! Just as long as you run it before launching to check for leaks.
But personally, I wouldn’t waste my time just doing risers. If you’re going to jump in there then you’re better off getting the whole kit with manifolds, risers, gaskets, bolts, etc., and starting fresh. Once you take the risers off the manifolds are easy. It’ll be a good time for you to take a close look at the hoses while you have it apart. Maybe your PS cooler and anything else in the raw water line too. I see your 320 is an 05. If you boat in salt or brackish water, aren’t the original owner, or don’t know for sure when these things were done, going through it all might be a good idea and save you some headaches down the road.
While I’m not a marine mechanic, I am a pretty competent do it yourselfer (at least with the gassers, diesels are a whole new world for me) and have done a bunch of work on my stuff and friends stuff over the years and other than failure due to raw water intrusion, not much else sends marine motors to early graves so IMHO it pays to stay on top of that stuff.
The 4cyl, 6cyl, and big block kits are pricey for what they are, but the small block OEM kits are a relative bargain and readily available from a lot of different places at competitive (maybe $600 or less) prices.

 

[sbw1]

No sh*t Sherlock! Since the OP didn't actually state what his boat use was (fresh or salt) or what kind of system he had (FWC or RWC) I made my statement which included my boat's type of use.

It's a Florida boat on the Gulf. Probably sees a lot of salt.