Engine won't turn over, no power

remove the hose from the bottom to drain it first, loosen the clamps from the riser and remove riser, for the manifold remove the 2 outer bolts and1 inner one have a helper hold it while you remove the last bolt, lift and remove.

To install, notch the 2 end holes of the manifold gasket so that they fit over the bolts if not already notched. hang manifold by 1 inner bolt to hold it in place.
Install 2 end bolts and remove inner bolt.
slip gasket between manifold and head, install 2 inner bolts, tighten all bolts,
Use Permatex Aviation sealant on the manifold, and riser gasket, install riser tighten bolts and clamps.

Ok, still working on it. Just got the riser and manifold removed. Before this, I turned the key to RUN, jiggled the wires at the starter and the radio came on. This has not happened before. Read 12.5 volts at battery, ignition and accessory terminal at key switch. I then tried to turn my bilge pump on, killed all power and read 0V at all B, I and ACC. Turned bilge pump off and voltage jumped to around 8V. Jiggled the wires again at the starter and voltage jumped back to 12.5V and radio turned back on.

FYI, I was jiggling the wires at the terminal where the orange alternator wire goes, red from battery and red to breaker.

Gonna get back at it and removed the wires from the starter, clean all terminal and wire ends. Feel like we're getting somewhere!

Removed the 90A fuse at the starter. This is what it looks like. It has been melting for some reason. Another issue I need to solve. Earlier this summer, I shredded my impeller and had to replace it. I was unable to find all the missing impeller vanes and since then, there has been a restriction somewhere (I believe) because the indicated water PSI has been very high 40 psi at 30-35 mph. Because of this, the engine has been running hotter than it should. It will reach about 178 degrees before I back off and let it cool down. When I back off the idle and then immediately increase the speed slowly, the temperature begins to drop rapidly.

Good find

if you have a loose connection there will be excess current draw and that would cause excess heat thus the melted fuse.

When you replace it make sure everything is clean and tight.

Find the incoming water line to thermostat, Cold water supply,
remove the line and stick a hose in it and back flush the water line. A piece of the impeller could stuck at the power steering cooler.

you have a on motor belt driven water pump assembly, the out put hose of that housing feeds the motor and connects at the thermostat housing.

disconnect the hose at the pump housing and back flush as described above from the thermostat side of hose.

Problem solved! The loose connection at the starter fuse was causing all my problems. I disconnected all wires from starter, cleaned them up, ran a new 6 gauge wire from the alternator to the starter and a new 10 gauge wire from the starter to the circuit breaker. Bypassed the 90A starter fuse (temporarily as I'm waiting on my new one to arrive). Now getting full battery power at all key positions (per the position of the key switch).

Amazing what a little corrosion can do, glad you found the trouble.

I know. Had no idea it could cause this much trouble. I try to look on the bright side. I've learned so much about my boats electrical system and also have some new parts!!!

Does the sealant only applied between the manifold and riser? I read where you do not apply any type of sealant between the manifold and engine block.

manifold to block is dry, riser to manifold, PermaTex aviation