HELP. 7.4 mercruiser tranny and engine oil

[BLKay]

355 carver. 1998. First day in boat was a disaster.
Must have picked up a rope on port side.
Rumble would not go away. So turned it off. Starboard side started showing about 10 oil pressure. Checked oil. On full mark. No oil on board from the guy I just bought it from. Ahhh.
Tried port engine again. Good for a bit. Thdd EX n rumble again. Turn off. Then try lower station to see if perhaps it didn’t go all the way into gear because of a cable. Nothing at lower. Try upper again. Nothing. Check cable. Broken right off.
Start engine and try to put it in gear to run. Shift Lever on tranny stuck or do it seems. Try to spin drive shaft. Nope. Try starboard to see if I can spin it. Yup. So must be fused on rope. I hope. Taking a peek today. If so hiring a diver.

Had to hobble in on one Engine with rudder. Tricky tricky in a tight marina. We were travelling about 30 mile to home. Made it half way. Hobbled into a marina after calling them.

And. Wife was cleaning the heads. Locked the front head door and closed it. Luckily the tiny window screen was so dated and not great. I ripped through with a extended prod and flicked the lock open.

Also the previous owner uses 10w30 in the engines. I read it was 20w45 ? No? We are in Vancouver island so it’s cooler here so I get that thinner oil is okay. But? Engines have 1350 hours. A bit low pressure so 20-40 would be better if think?

Also an oil leak I can’t find. The starboard that was on the fill line. We thought it was the fittings around the oil filter. Nope. Oil was around that area. He just did the exhaust manifolds so figured it was the filter fittings he had off? Not sure. But they are tight. Just a bit of used oil in the bilge. I checked the filter tightness. Perhaps the seal is messed up or as I’ve seen happen the oil seal was also left on under neath.

So much to learn on this boat. 100 switches on that panel. 48 Hose levers

Any advice appreciated

[Viper]

Use 25W-40 for those engines. I wouldn't trust what you see at the pressure gauge until you confirm with a mechanical gauge at the engine.

Oil could be coming from anywhere. It's a matter of wiping everything down, then put some white oil absorber sheets under the engines. They'll give you a general idea of which area the oil is coming from, then it's a matter of looking closely. above that area. Certainly oil lines are suspect but so are rocker covers, original filter mount on the block that the remote filter hardware hooks up to, rear main seal, remote filter assembly, etc. There are more hi tech methods too such as adding dye and using a light to detect leaks.