There's really nothing in the outdrive assembly that would allow turning in one direction but not the other.

2X on the age of the boat...that said, its likely the cable is worn out. try loading...

based on item 6 in post #1, its highly likely the carb is in need of a rebuild...with a high idle speed, the idle mixture screws should have little (if any) control ...

The material I read today suggests the IAC function has been incorporated into the digital/electronic throttle control subsystem....I'd be inclined to concentrate the troubleshooting to those...

There may not be a stand alone IAC...I'm thinking the DTC subsystem may incorporate that function...

and something sticking/being gummed up is always worth checking...and eliminating...

I'd rule out vacuum leak as the idle speed is low (vacuum leak = more air = increased RPM).

I'd suggest starting with the RINDA unit and use the STBD engine to get some baseline data...say lowest...

you can usually tell by looking at the bevel on the teeth of the ring gear...

The bulletproof method is to remove the plugs and the rocker cover for number one. spin the crank one way and watch...

indeed, especially after 3+ decades.

I would seriously consider a major overhaul when the engine is removed for repair...

think you are on the right path...I would suspect the input shaft is hung on the damper plate (or coupler) which is bolted to the flywheel.

Typically, one removes the perimeter bolts attaching the...

That suggests your service intervals should be more frequent...hopefully, it will all go back together just fine...

if you have the new parts, you can usually make a good guess on where the old parts end...a hooked pick can also be useful for pulling some of those seals...if the seal is metal cased (around its...

ok...sounds like there is a short between the battery's positive loop and the ignition circuit...

I would start by separating the large connector in the main engine wiring harness (connecting the...

If its the audio warning horn, then it sounds like the wiring in the dash has gotten loose (maybe).

reconnect battery and then find the horn, if its going off - if its standard mercruiser stuff,...

if the snap ring (12) isn't there, the washer and the seal should come off the shaft...

is the washer loose (axially)?tried lifting the washer with a 90 degree pick?

I'd say go with the current NGK recommendation...if it doesn't perform as expected, you can always open up the gap a bit (if they are the old normal style - no platinum or iridium ends on the...

really depends on what the plugs are going into and if the ignition is 'stock'...

I'd check the prop first...if the coupler was gone, I'd think you smell it in short order with that much slip...

Did the 'guilty' yard own up to the mistakes?? Agree to make the YC 'whole', in a finite period of time?

you can get the GM performance gen V replacement for under $200...

Moving the ring gear isn't hard, just need to take your time...any machine shop can do it for a small fee.

The other option is...

if you are referring to your damper plates (bolted to the flywheel), yes they wear out (and otherwise deteriorate). If yours are original you'd be crazy to not to replace them while the engines are...

I think I'd check the ignition and if the spark is present, then it suggests the injectors are not firing...

After cranking it a few times, you should be able to smell the fuel in the throttle...