4.3 GL-C ran for extended period with raw water hoses installed backwards

I just bought my first boat, an 80s bay liner trophy with a newer 4.3 installed. When I bought it the raw water hoses were disconnected and I reconnected each one to the closest connection.

I started the motor for the first time yesterday using the hose connection in my drive way and let it run for 10 minutes or so and the temp gauge got up to 180f.

Today I put it in the water. I let it idle for a few minutes and then headed out in to the lake through a no wake zone. Temp gauge was reading below 180F.

When I made it into the lake I accelerated to about 2500 rpm and was starting to get on plane. Then I noticed smoke coming from the engine hatch. I put it back in idle and shut it down. The rubber exhaust connectors at the outlet of the manifolds were melting and everything was to hot to touch. The temp gauge on the dash read about 185F.

I let it cool down with the hatch open and used the trolling outboard to motor back in.

After looking at everything I now believe I put the hoses on backwards. The Volvo Penta shop nearby can’t look at it for a couple weeks and while I am waiting I can’t help but wonder if I just destroyed this engine. Is there any chance I didn’t?

Thanks,
Brian

For sure the raw water pump impeller is toast. open it and find all the pieces of the impeller if the impeller is not intact.
The water temp gauge reads the temperature o f the water in the engine.... no water in the engine... reading is ?????

I NEVER run an engine DIRECTLY on a hose with an engine with an engine mounted raw water pump.... the pressure ( 35 psi +) out a garden hose covereth many evils. I connect a hose from the raw water pump input to a 5 gal pail that also has a garden hose free running into it. This way I can SEE if the raw water pump is actually working. Be advised that most garden hoses can't keep up with the usual 40 GPM (WOT) water requirement of most V8s, sometime won't even keep up at idle.

I'm thinking your big issue with overheating the block and pistons may be ring seizure. Likely the oil control rings seizing to the pistons. It's hard to determine over the net. Sometimes ya' get lucky. If you weren't smoking blue out the exhaust, ya' might have a shot.
I think I'd pull the plugs, add some light weight oil to all the cylinders and turn the crank by hand a few rotations with all the belts off. Check for any binding at all. If that feels OK, a compression test would be next. If that checked out, change the oil and filter.
Get your cooling system corrected. Some images and part number matching may help determine hose routings.
.......
Copy and paste the link below then swap the two asterisk letters in "marinepart*e*press." This site won't allow those letters together it seems.
Volvo Penta Schematics | GAS | 4.3GL-A_4.3GL-B_4.3GL-C_4.3GL-D | COOLING SYSTEM (marinepartxespress.com)

Doubt that you killed it. The oil is going to protect the bottom end and I think you caught it before it did any real damage. Unfortunately the damage that you have done is going to cost many hundred clams for new hoses, gaskets, impellers, oil change and such. Then the labor to install it, of course. I'd guess that your little error will end up with a bill somewhere around 2-3000 or so. There are plenty of water flow diagrams out there to help you with hose routing. I suggest that you get started learning how to wrench your own stuff.

Thanks for all the feedback. It was a very stupid mistake on my part. I absolutely should have checked the routing against a diagram but it seemed obvious at the time which hose had been removed from which connection.

I am dropping it off at the mechanics today but he probably won’t have time to look at it until after Memorial Day. I’ll post a follow up after I find out the damage.