Sea Ray

270SDASE · ‎10-25-2020

I have a 1998 Sundancer 270DASE (single 7.4L MPI, Bravo 3). It’s always been in fresh water and maintained very well. The bottoms of the exhaust manifolds are rusty to the point of thickness flaking off. There’s plenty of space for access since it’s a single engine. Looks like there are 2 bolts a couple inches apart from each other for each exhaust port for a total of 8 per side. Does that sound right? I’m wondering if you have to remove the valve covers to access other manifold bolts? Any tricks to replacing the exhaust manifolds & risers. Any other items to check while in there?

wingless · ‎10-25-2020

The single engine 7.4L 270DA has plenty of access for swapping the exhaust. Valve cover removal not required,

There are bolts on each side of the exhaust ports, retaining the manifold to the cylinder head. On my 2000 380DA w/ the 454 (7.4L) MAG MPI Horizon engines there is also one single port heat shield retained w/ special fasteners, bolt on one side, stud on the other.

Each part is individually heavy, so start at the top removing the elbows, then risers, then manifolds.

Do a visual inspection for corrosion on the valves after manifold removal. Perform a valve job if required.

Inspect the raw water hoses. Ensure they are supple, not hard or crunchy and in good condition. Visually inspect the interior for scale. Replace as required.

Use the correct gaskets (solid or slotted) in the correct orientation.

Ensure the head gasket surface is clean prior to reassembly. All other parts are probably new, so no issue on those surfaces.

The exhaust manifold is big, heavy and awkward. A second set of hands is useful. I use a ratchet strap to ensure the parts have sufficient alignment at assembly. Do NOT cross thread the bolts.

270SDASE · ‎10-25-2020

Thanks wingless. I hope they put anti seize on the manifold bolts and none twist off...

wingless · ‎10-25-2020

YW

Yes, usage of an appropriate thread protector is handy. It must be compatible w/ the exhaust temperatures, like this product.

https://www.rvautoparts.com/77134-Permatex-Anti-Seize-Lubricant-Used-For-Exhaust-Manifold-Bolts_p_374858.html

When I did the first manifold replacement on my boat I swapped to Grade 8 bolts w/ armor coating, except for the special fastener retaining the small heat shield. Those fasteners have remained slippery enough not to need the thread lubricant.

My assembly always uses a torque wrench to the correct tightness.

I've used those lubes on automotive exhaust parts and don't like the smoking after initial usage, so in the boat I find that too scary for usage consideration.

wingless · ‎10-25-2020

My method for a fastener that doesn't loosen immediately is to instead first tighten the fastener, just until it moves the smallest amount. I then loosen and tighten, over and over again, on increasing range of turns until the part is removed.

On the plus side, these bolts pass through clearance holes on the manifolds into the cylinder heads.

If they are problematic in any way, the safe measure is to stop attempting to remove, then cut off the bolt heads, slide off the manifold, then directly apply a liberal amount of lubricant while using lock jaw pliers to remove the remainder of the bolt.

270SDASE · ‎10-25-2020

I was already anticipating my options for a twisted off fastener, and figured I could do as you mention about cutting off the problematic heads to then access the fastener shaft with vice grips. I like the thought about tightening the loosening repeatedly too. I have a 2000F anti seize for exhaust sensors.

gregk · ‎11-01-2020

I have used the approach wingless used. Many times a slight tighten helped. If you feel allot of resistance, stop or it will likely snap.

Tung · ‎05-30-2021

I need to do the same. would love to hear how it goes and any learnings/photos/videos would be amazing.

Sea Ray

I have a 1998 Sundancer 270DASE...