Seized 1989 Mercruiser 350 MAG. What should I do???

[THATDONFC]

Hi everyone, it seems as if the engine is seized on my 20 ft ski boat. The boat has a GM 350 MAG mercruiser sterndrive engine.

Some back story:

I took on some water a while back and the engine swallowed a bit of it. I'm not sure how as the engine was not running. Anyways, I pulled the plugs the next day and cranked the engine and it spit a lot of the water out. I tried starting it after the water stopped and it wouldn't fire. It cranked just fine but wouldn't start. I let the boat sit for a month and came back to find the engine won't turn. The engine is stuck pretty good and I don't think there is any way to break it free without removing the engine. I made a tool to bolt to the 3 crank pulley bolts that would accept a 1/2" breaker bar. I put some good torque on it in both directions and nothing. I also soaked the cylinders in p' blaster over night but it didn't free her up.

My question is, what are my options? Do I remove the engine and replace it with a new long block or try and salvage the current engine. Would it be a bad idea to buy a long block and transfer all of the other parts over from my engine? Is it terrible that I want to pull the engine and rebuild the block with new pistons, rods, bearings? I have the knowledge and tools to rebuild the engine/swap parts to the new long block. I don't however, have a hoist to pull the engine from the boat. I spoke with a few boat mechanics and they said I should be okay pulling the engine out with a forklift.

I'm looking for the least expensive way out here. I don't have a lot of cash but i think I can afford a long block. I found a few sites online which list them around $1.5k A couple of my friends also offered to chip in on the repair.

Thanks for your time and help. I appreciate it greatly.

-Chris

 

[Bt Doctur]

Where do you live?

 

[Bt Doctur]

Where do you live? I took on some water a while back and the engine swallowed a bit of it. I'm not sure how as the engine was not running.
How much water?

 

[THATDONFC]

I live in Venice CA. The boat is stored in Marina Del Rey at the moment.

The water came as high as the floor of the boat. The floor is about level with the center of the crank pulley.

 

[DJ Jaws]

I seem to be the seized engine king lately. If it's to the point where you can't turn it anymore, there's some serious madness going on and nothing is going to fix it except elbow grease.

The first thing I would do is strip down the top end, pull the heads and see just how bad it is. With cold water in a hot cylinder, you may have warped a few major elements, like a cylinder wall. It is also probably pretty rusty by now. Depending on how bad it is, you may or may not get it to turn.

The easy thing to do is get a used running motor. There are plenty of them around. In all likelihood, you will have to pull the motor and take it to a machine shop. You should be able to pull the crank and drive the pistons out the bottom one at a time. If the block is really bad, they can bore and sleeve the cylinder walls, or they may recommend replacing the block entirely, depending on the severity. If not too bad, you can just bore the cylinders. Also have them check the plane of the top and plane the heads. Then you can rebuild with new pistons, rings, bearings, etc according to the sizes you get machined. You can get a rebuild kit on ebay with the works for about $500, complete with pistons, rings, and everything.

I'd guess that you are in it for about the same cost, whichever route you go. I'd rebuild it, but that's just me. I like knowing exactly what I have, rather than buying someone else's headache.

 

[Fishermark]

You can either rebuild or put a new engine. I personally would not go with a rebuilt - or even a long block as you can buy a brand new crate engine for about the same price. (The basic crate engine is for a truck, which is appropriate for a boat).

But like DJ recommends, I would pull the heads and see what kind of damage you are looking at first.

 

[THATDONFC]

I'll take your advice and tear the engine down from the top down. If I do find that the engine is no good, where's the best place to purchase a new engine. I'd prefer a long block rather than a complete turn key engine.

 

[Watermann]

You're going to need to think about the stern drive too, you probably have water in the bellows as well with a rusted gimbal bearing and U joints. I would pull the drive off and see if the motor will turn without it also being rusted up.

 

[Fishermark]

I'll take your advice and tear the engine down from the top down. If I do find that the engine is no good, where's the best place to purchase a new engine. I'd prefer a long block rather than a complete turn key engine.

I'm not suggesting turn key - that would be expensive. Here's a new engine that is more than a long block. The cost is about $1,700 with free shipping - but you can shop around and maybe get a better deal. It already has brass core plugs, composite head gasket and a cam suitable for a boat.

 

[THATDONFC]

A quick update for you guys. I pulled the sterndrive off and I was still unable to turn the engine by hand. I then took the engine apart from the top down. Pulled the heads off and found a good amount of rust in the port cylinders. I'm assuming the rings are rusted to the cylinder walls. Time for the next step.

I've decided to remove the engine and rebuild it with an .030 overbore. I've built about a dozen high performance BMW engines but I am fairly new to marine engines. I'd like to get some input from you pro's as to which parts I should use for this rebuild.

Is there a brand of piston that is recommended for the Mercruiser 350? I don't plan on building a high performance engine, I just want a nice reliable motor. I plan on purchasing an entire marine gasket set. Is there anything I should look out for while the engine is apart? What are the parts on these Mercruiser 350's that fail regularly/prematurely? Also, is it difficult to break a fresh motor in on the water? Should I take it to someone with a boat dyno to break it in?

Recommendations for these parts would are appreciated.

Pistons, rings, gaskets and anything else you can think of.

-Chris

 

[THATDONFC]

Should I replace my exhaust manifolds? I'm sure they are fine. The boat has lived in socal since it was new so I don't think there is any chance they would freeze crack.

 

[Bondo]

Should I replace my exhaust manifolds? I'm sure they are fine. The boat has lived in socal since it was new so I don't think there is any chance they would freeze crack.

Ayuh,.... Welcome Aboard,... In SoCal, Saltwater, 'n rotten manifolds is the problem,....

A quick update for you guys. I pulled the sterndrive off and I was still unable to turn the engine by hand. I then took the engine apart from the top down. Pulled the heads off and found a good amount of rust in the port cylinders. I'm assuming the rings are rusted to the cylinder walls. Time for the next step.

I've decided to remove the engine and rebuild it with an .030 overbore. I've built about a dozen high performance BMW engines but I am fairly new to marine engines. I'd like to get some input from you pro's as to which parts I should use for this rebuild.

Is there a brand of piston that is recommended for the Mercruiser 350? I don't plan on building a high performance engine, I just want a nice reliable motor. I plan on purchasing an entire marine gasket set. Is there anything I should look out for while the engine is apart? What are the parts on these Mercruiser 350's that fail regularly/prematurely? Also, is it difficult to break a fresh motor in on the water? Should I take it to someone with a boat dyno to break it in?

Recommendations for these parts would are appreciated.

Pistons, rings, gaskets and anything else you can think of.

-Chris

Ya really should consider the Long Block replacement, like Mark posted,....

Especially if that motor has been run in the Brine,....

As for breakin' in a motor, a Boat is the near perfect Dyno,....

 

[HT32BSX115]

Should I replace my exhaust manifolds? I'm sure they are fine. The boat has lived in socal since it was new so I don't think there is any chance they would freeze crack.

Well, you said "Marina Del Rey"

That's salt water (Which is why the engine was destroyed sitting with [salt] water in the cyls for a month)

It also means that your manifolds and risers could likely be very rusty too!

Unless they're only a year or so old, you should replace both the risers and manifolds if they're rusty in the jackets. You'll know when you break them apart (remove the risers from the manifolds ) and look in the jackets. If you see a LOT of rust like they're clogged, It's time for new ones. Don't try to "clean" the rust out.

Also, if the manifolds/risers are rusty and they're original, the block, heads, intake manifold and water-circulating pump may be as rusty too.

I'm looking for the least expensive way out here. I don't have a lot of cash but i think I can afford a long block. I found a few sites online which list them around $1.5k A couple of my friends also offered to chip in on the repair.

The least expensive way out would be a wrecking yard pickup engine! If you rebuild, just buy stock parts. The 350 is one of the best engines ever put in in front of a sterndrive! If that's a flat tappet engine, and you rebuild, you'll want to follow the cam manufacturers instructions. If it's a roller engine, you'll only be breaking the rings in....... Then you break it in like any other engine (but DO NOT "BABY" IT)


Cheers,


Rick