Pulling Riser on 3.0L Mercruiser

[enginesilo]

I'm having some high temperature issues and I am planning on diagnosing the boat by pulling a few of the raw water lines one at a time in a few strategic spots to see if they are flowing well while running, and next I am planning on pulling my riser off. Can anyone share some quick tips?

From what I can see in the parts diagram, it look like 2 screw clams that hold the riser tot he exhaust tube need to be loosened, and then only 2 bolts that hold the riser to the exhaust manifold. Is that it and then it pops right off?

When replacing do I only need the 1 gasket where the riser and the exhaust manifold meet?

I've been told if I pull the riser I should see just how bad the corrosion is inside of the riser, and some of the exhaust manifold.

 

[dubs283]

remove all four hose clamps at the exhaust boot and slide it down the exhaust tube, then loosen all four nuts that hold the riser to the studs and remove the riser

have you already inspected/replaced the sea water pump/impeller??

 

[enginesilo]

remove all four hose clamps at the exhaust boot and slide it down the exhaust tube, then loosen all four nuts that hold the riser to the studs and remove the riser

have you already inspected/replaced the sea water pump/impeller??

Thanks for the tips, I was planning on only loosening the top 2 clamps so i'll go ahead and loosen them all. Do I risk dropping the exhaust flapper in at that stage of sliding the boot downward? Mine only has 2 bolts that go from the top and directly into the exhaust manifold, but I have seen the type you are talking about where the entire stud can be seen on the side.

Can I reuse the clamps and that rubber boot? I think the answer is yes but wasn't sure since i've never done this before. If only inspecting and it turns out to be ok should I reuse the same bolts or buy new? When replacing the riser with a new gasket is any sealant needed like a Permatex or anything?

I changed the sea water pump/impeller last season and the problem remained. Riser gets super hot. I've only tried on the hose this year but it seems like the temp is creeping higher than usual.

When I start the boat on muffs should there be water coming out the back after the system fills up, say 15-25 seconds? If I am understanding how the thermostat housing passes water, much of it bypasses the engine and goes straight to the manifold and riser, so water shouldn't have to wait till the engine gets up to temp for the thermostat to open, correct?