REVIEW: Everything Wrong With A Mercury Mercruiser

What engine should we review next?

Will never own one of these, this will never affect me, yet here I am.

HUGE NOTE TO ADD. The starter, alternator, carb overflows were different than a truck or cars. They are supposed to be marine grade so there’s no open spark risk. The carb needs to have the jhook on the overflow in the event your floats stick open. Insurance used to cancel claims due to inspection’s showing non marine parts were used

Back before we had kids and I could afford to put gas in a boat I pulled the perfectly fine 350 small block and put a 383 stoker kit in. My wife was not pleased, I was very pleased with the end result.

That was awesome! Im a retired disabled MERCRUISER mechanic, you brought me back to the shop! You covered basically everything! The one thing I'd brought up is the "CORROSION SPAYS?" And fuel stabilers, thank you for the journey back to the best years of my life. Nice shop! I'd bet alot of dreams came threw there. Keep up the keeping up!!

I work on alot of these and 100% agree with you the biggest issue they have is poor winterization and maintenance

As these engines get older internal scale will form that often plugs up the block drains and manifold drains. Use a small screw driver to poke into the opened petcocks to ensure all the water comes out. On the later models with connected hoses to a single drain remove the quick connect hose connection on each side of the block and insert a small screw driver to move the scale and allow the water to fully drain. I learned this the hard way and was told how by seasoned marina mechanic what I needed to do in the future.

I had an old wakasha/ford 302 in a boat. I put a thermostat in it. Got a little better efficiency, but more importantly I got hot water to put in the wetsuit before jumping into the 5 degree Celsius lake.

30 plus years ago i did enjoy being on my friends boat powered by the GM 4 cyl Iron duke. It could pull 2 skiers and would run all day on 20 gals of fuel and was quiet

Another common issue with these engines is the oil pan will rust away and pour oil out, requiring an engine out job in most cases! Awesome video!

Been on the same 350 Merc for 30 years... Thousands of hours, all original right down to the plugs and wires for over 25 years. The only problem we ever had was the raw water pump and finally a hairline crack in one of the cylinder heads. Just goes to show if you take care of it it'll take care of you.

I worked on these for over 10 years and was certified on Mercury outboards and Mercrusiers . Went to merc school in Dallas. In school we were told the only internal parts that were changed from the GM engine was the camshaft that made its power mainly in low to midrange around 4200 rpm’s. And installed Stainless steel valves.

Brings a smile to my face to see some marine content on the channel! Mercuiser didn't continue on with the LS line of engines but volvo penta did. Took a long time but all modern gasoline I/O's are running catalysts as well now. Albeit they are falling by the wayside of the simplicity, servicability and reliability of modern outboard engines . Im sure youve got a good marine contact near by you but if you ever have any questions dont hesitate to reach out - northern ontario based marine tech of 14 years 👍

That definitely gives me a higher appreciation of what Mercruiser has done with these engines. It is great to see how you speak directly to us backyard mechanics.

Back in the 90's I worked at a local marina. We did hundreds of winter/summerizations on boats and had large storage buildings for winter. I think I still have fiberglass shards in my forearms from reaching around the larger engines stuffed into the fiberglass boats. We (the young mechanics and helpers) always preferred to work on the Mercruiser stuff, and specifically the Cobalts. They were simply a better built and better engineered pleasure boat than any of the others at the time. Bayliner and Maxim were always the worst. We called them the "Kraco" of the boating world.

I used to build the 3.0L I4 mercruiser engines for sprint cars, good engines.

You did an excellent explanation of the mechanical differences between automotive and marine engines. But you forgot an crucial difference, the electrical system. The electrical systems for marine application, not only the engine, is different than automotive. The engine bay of a car is very well ventilated, you can see the ground when you open the hood. For a boat, when you open the engine bay of an inboard like yours, you see a solid sealed (hopefully) hull. There is nowhere for the gas fumes to go. This is the main reason for activating the venting fans before starting your engine. The electrical system of a marine engine is specially designed to avoid the electrical arcs of the various form of switches to be in direct contact with the surrounding air. Even the wires are different, each braid is individually tinned to prevent corrosion. Never use a car alternator, marine grade alternator will have double insulation to prevent shock and sparks. Rich, be careful with the LS swap, use marine grade electrical system.

I took out my cracked 5.7 and completely built a 383 stroker along with Corsa 4” side exhaust. What a monster!!!

Nice! Good to hear positive comments towards mercury engineers, as my GF was Mercury's original chief engineer.

My current boat has a $75 junkyard 4.3 from a blazer. I put it in 4 years ago and it's been phenomenal 😂