MainShip 31' Sedan Bridge - Risers Mainfolds

[jlombardo]

I own a 1998 Mainship 31 Sedan Bridge with Marine Power 350 EFI engines. I did have new Quicksilver long blocks installed about 4 years ago. I am hoping that someone familiar with this boat can provide links to the specific exhaust manifolds and risers that I need to purchase.

Any help would be appreciated.

Happy Thanksgiving all!

Thank you,
John

 

[Crux]

The 350, aka 5.7, is likely the most popular engine ever marinized. Its the base
engine for Marine Power, Merc, Volvo, Crusader, etc.

Many aftermarket manifolds offered, but to avoid china junk I would stick to Mercruiser.

Manifold riser height is determined by the builder to provide proper height above boat's true, actual loaded waterline. Height adjustment is offered with 1" , 3" , 6"
riser spacer kits.

Here's a good place to start looking..
https://www.michiganmotorz.com/products/marine-parts-accessories/exhaust-manifolds-risers

Whether your engines are raw or freshwater cooled will affect the way manifolds are plumbed.

Mercruiser offers a 'dry joint' style which eliminates problems with earlier manifold-to-riser gasket. It may be a good time to make the change....the M Motorz folks will
be happy to help you.

 

[jlombardo]

Crux,

My engines are fresh water cooled.

My issue is that I have been burning antifreeze since I purchased the boat over 6 years ago. I had the motors replaced with long blocks and they supposedly replaced all hoses and exhaust manifolds/risers. Even after that I found that there was still a small amount being burned and after 2 years it did get worse. When I brought it back to the marina that did the engine over hall, they said that I needed to replace the riser gaskets, so another $1200 to find that I am still burning antifreeze. A knowledgeable guy on our dock suggested that it could be risers/manifolds. I did remove all plugs and it does appear that the 2 inner plugs on all sides do appear to have some rust. Based on some other items, I would not be surprised if the marina that did the motor work simply painted the original risers/manifolds and reinstalled them.

I am very interested in learning more about the Dry Joint option. When I had the riser gaskets replaced the mechanic did show me the old gaskets with a little heat crack in them. He said that the engines seem to run hot causing this condition. Maybe dry joints will help this.

Thanks for the information! I will definitely engage the Motorz folks.

John

 

[Turtle Blues]

Basic Power website is ebasicpower.com They have individual parts or full kits. In your case it sounds like that would be the best way to go. There is no way to know the internal condition of riser parts, even when you have them in hand. It's just easier to replace everything. Reasonable expense in the long run.