Dri fit and new Risers questions.

[pacofortacos]

I have a 96 Cobalt 4.3 mercruiser.
Currently have a wet fit exhaust with closed cooling so only the riser sees salt water.
Risers are several years old now and this boat is only used for 1-2 weeks a year in salt water and then sits on the trailer.
I also have been fighting a leak between the manifold and risers from day 1 with the new manifolds - so obviously one of the parts just probably isn't machined perfectly.

SO with all of that being said, I am going to go to the dri fit system and have ordered
Barr MC-1-864612 manifolds and Quicksilver Mercruiser 864309-C risers.

So 2 questions:
1. Are those the right parts to convert my wet joint to dri joint? They seemed to be from what research I could come up with.
2. Has anyone tried Jet Hot Coating their exhaust?
They say lifetime guarantee and salt water will not be a problem after.

Cost for the risers to be done is just under $400

OR

Painting the inside of the risers with Rust Bullet?

Opinions?

 

[alldodge]

Agree, those should work

Have not used the coatings, and don't see the need provided surfaces are flat. Use a straight edge and check for flatness

 

[pacofortacos]

Sorry maybe I wasn't clear on what I was considering doing.
I am not worried about the riser to manifold surfaces.

Since the riser is the only thing that sees salt water, I was wondering if having the water passages internal to the riser coated would be something to do.
Risers are new and if I can keep them from rusting, it would be a win.

Jet Hot says they can do them and lifetime guarantee - BUT I think the guarantee is only on the finish not on what they coat.
I don't know how well they can get at the internal passages.
Another option is to buy a gallon of Rust Bullet and just dunk the entire riser into the paint a couple of times.
OR do nothing and watch them rust away.

They are OEM quicksilver Mercury Risers if that matters.

 

[Searay205]

Coatings are hit and miss mostly miss in the consumer market. I had a long talk with a Mercruiser Engineer who said Mercury developed a coating back in the early 90's. Goal was to guarantee 3 year manifold life in salt water. He broke off from Mercruiser and now represents the company that does the coating. I believe the guy worked for Mercury, he lived near stillwater Oklamha etc. He said the key with slat water is keep water temp below 140F, above that the salt crystallizes, said the bond is so strong your not washing it away. My manifolds have the coating and let me tell you there is zero left. I wouldn't waste my money. As far as his company and coatings, real hit and miss, sometimes works great other zero success. He said for me to send him my manifolds and he would coat it was around $400. Manifolds of your era should go 225 hours or 10 years from the failures I have seen, just my opinion. I guess you just replace risers, that cheap.

 

[pacofortacos]

Thanks, that's what I was afraid of.
My manifolds should last the life of the boat as they are full of antifreeze.

Hmm, I really have no clue as to what the temp the risers would be running at, I would think below 140. There thermostat is a 160 but that is for the engine and manifolds.
The sea water goes in through the outdrive, through the PS cooler, then the heat exchanger and then to the risers. Water is probably in the 80's-90's incoming.
I will have to try to remember to take the infared gun and see what temp the hoses going to the risers are running at.

Cost to Jet Hot the risers would be around $400 - worth it if they could guarantee it would work. I just don't know if they can access all of the internal area for the coating to stick.

 

[Lou C]

I think you will find a big difference in elbow temp idle speed vs right after coming off plane. Idle might be close to 95-100 but after coming off plane 135 is typical but only for a few minutes, they will cool back down in a few minutes of low speed running. In your case I don’t think I’d change from the exhaust you had due to the fact that you already have full closed cooling I’d buy better quality elbows and check the flatness of all surfaces before installation. If you had raw water cooled exhaust including manifolds then yes it would make sense to change to dry joint. However the dry joint elbows do corrode through just like wet joint elbows. The main advantage to the dry joint system is in raw water applications due to the separation of exhaust gas and cooling passages.When I installed Barr aftermarket units on my OMC I checked them and found they were flat to less than .001” which is excellent.
Here in salt water I have always changed my exhaust from 5-7 years of use and never had water in a cyl from bad exhaust, even with the original OMC one piece units which have a reputation for failing just like the Merc V6 units.

 

[pacofortacos]

I considered that but got these parts very reasonable and they are new .

Do you know if the dri fit gasket is the same bolt pattern as the wet fit? I know they won't interchange just wondering on the bolt pattern/spacing.

Some body will be getting a good deal on my wet fit manifolds as they have had antifreeze in since day one new when they were installed.
My risers might even be good yet - I don't have access to the boat it is in storage.

I have fought that manifold to riser gasket too long and too many times lol. It wins.

 

[Lou C]

There are kits to change from the wet joint to the dry joint; the gaskets are totally different. You most likely have to change the hoses and exhaust pipes that connect the exhaust elbows to the Y pipe. Do a search on this, i think Merc and Barr marine sell kits to convert from the wet to dry. I have the late OMC/Volvo wet joint and they have not been problematic with leaks. 3 years so far..

 

[pacofortacos]

Risers came in today.

It should be a really simple install, when I go to do it.

 

[Lou C]

Ah checking back I might have been mistaken, I was thinking of the conversion from the Merc one piece V6 manifolds to the 2 piece units, that involves different hoses and exhaust pipes that make up a kit for the conversion, to do what you want it seems like its a straight swap. Just have to make sure the down angle of the elbows is the same I guess.

 

[pacofortacos]

That's what I am hoping, the ones I bought are the 2002-2004 7 degree down risers.

I might try to jamb brass freeze plugs into the manifold to riser holes - plug both the manifold and riser holes.
Either that or tap them and plug them - 1 less possibility to leak and easy to do at this stage.