Mercruiser manifold and risers too far gone!!

willciviceg5

Hi, looking for some advice I just pulled off the risers last night and found this, obviously they are bad and need to be replaced but I have to put the boat in the water this weekend, i will only drive her from the slip to the mooring which is less than a half mile.
So can these be replaced while in the water? Do I have to replace the manifolds as well as the risers? And is there anywhere in Ireland with these available for a reasonable cost?

fergal.b

They look pretty clogged up but you might be able to make a short trip if you keep your revs down and keep an eye on your temp, you can get replacement ones here https://marineparts.ie/engine-parts/mercruiser/exhaust-system/manifolds-and-risers-mercruiser/ they are in Swords Co.Dublin and will deliver.





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willciviceg5

fergal.b wrote: »

They look pretty clogged up but you might be able to make a short trip if you keep your revs down and keep an eye on your temp, you can get replacement ones here https://marineparts.ie/engine-parts/mercruiser/exhaust-system/manifolds-and-risers-mercruiser/ they are in Swords Co.Dublin and will deliver.





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Thanks a lot for the reply, will it be possible to do these in the water?
Also how do I know what risers I need, it looks like there were replaced at some stage so I can’t see part numbers. I found a company in England that have the kit for a really good price.


https://repowermarine.com/index.php/parts-for-mercruiser/mercruiser-petrol/mercruiser-exhaust-system/manifolds-riser/manifold-riser-set-for-mercruiser-5-0l-5-7l-v8.html

fergal.b

Yep you can do them in the water, if they are mercruiser V8 you have 2 choices 5Lt or 5.7. you could try cleaning them with electrolysis or bring them to a machine shop somewhere like http://www.howardengineering.ie/

sogood

willciviceg5 wrote: »

Hi, looking for some advice I just pulled off the risers last night and found this, obviously they are bad and need to be replaced but I have to put the boat in the water this weekend, i will only drive her from the slip to the mooring which is less than a half mile.
So can these be replaced while in the water? Do I have to replace the manifolds as well as the risers? And is there anywhere in Ireland with these available for a reasonable cost?

You might want to pull your plugs and check for any water in the cylinders. Turning the engine with the plugs out (and the distributor lead grounded) will push any water out. It's a by product of a failed riser/gasket where exhaust water can get back down into the cylinders as exhaust gas is coming out.

Excessive water in the cylinders can cause a hydrolock and result in a bent connecting rod or worse. Those risers do look very bad and be aware of the right gasket for your set up. One type has four slots and another type has two slots and two small holes, despite the riser having four slots. While not life or death, using the wrong gasket can cause the engine to run cooler or hotter.

willciviceg5

sogood wrote: »

You might want to pull your plugs and check for any water in the cylinders. Turning the engine with the plugs out (and the distributor lead grounded) will push any water out. It's a by product of a failed riser/gasket where exhaust water can get back down into the cylinders as exhaust gas is coming out.

Excessive water in the cylinders can cause a hydrolock and result in a bent connecting rod or worse. Those risers do look very bad and be aware of the right gasket for your set up. One type has four slots and another type has two slots and two small holes, despite the riser having four slots. While not life or death, using the wrong gasket can cause the engine to run cooler or hotter.

Thanks for the advice that was the worry, hopefully the plugs aren’t too bad to get out.
How do I find out which I need, one company said slots and holes and the other said slots, both were using the engine serial number

sogood

willciviceg5 wrote: »

Thanks for the advice that was the worry, hopefully the plugs aren’t too bad to get out.
How do I find out which I need, one company said slots and holes and the other said slots, both were using the engine serial number

Yes, been there and done that. Varying opinions abound! I had replaced my gaskets as part of a resto and used the 4 slot variety, based on info from a supplier. Running on muffs with no issue, except that the engine took a while to get up to temp and ran a little cooler than expected. So, only today, I had reason to remove the risers and replaced the gaskets with the two hole/two slot variety, following more googling and advice/suggestions from people in the know.

For a reference point, my engine is a 1990 Mercruiser, 5.7 V8 with a raw water cooling system. I don't have a serial number as the tag was missing from the time I got it, which hasn't always helped with parts identification!

Whereabouts are you based? I'm in Kenmare.

willciviceg5

sogood wrote: »

Yes, been there and done that. Varying opinions abound! I had replaced my gaskets as part of a resto and used the 4 slot variety, based on info from a supplier. Running on muffs with no issue, except that the engine took a while to get up to temp and ran a little cooler than expected. So, only today, I had reason to remove the risers and replaced the gaskets with the two hole/two slot variety, following more googling and advice/suggestions from people in the know.

For a reference point, my engine is a 1990 Mercruiser, 5.7 V8 with a raw water cooling system. I don't have a serial number as the tag was missing from the time I got it, which hasn't always helped with parts identification!

Whereabouts are you based? I'm in Kenmare.

I'm in St. Mullins in Co Carlow, it will be interesting to see what gaskets arrive with my manifolds and risers.

sogood

Would I be right in thinking that you're in freshwater so? If that's the case your risers should last a good deal longer. I'm in saltwater, but hoping that the brackish water in the harbour will hopefully go some way towards flushing my system when I return from the high seas ( Kenmare Bay)!!

Last year I came across a pair of used, but very clean manifolds and risers, so I took them as a spare set. Nice to know I can swap them out at the drop of a hat without any major expense.