OMC Sea Drive locked up

Tiderunner18 · Feb 24, 2007

This morning, I drug home a 1985 18' Tiderunner with a OMC Sea Drive (140hp, I think?) that hasn't run in a good 10 years or so. The motor is locked up so I started with shooting lots of penetrating oil in the spark plug holes but only managed to get the flywheel to turn back and forth a degree or two. I pulled the heads off and the cylinders had a little surface rust but nothing terrible so I'm thinking the pistons aren't siezed. Any ideas what might be locking things up? Broken crank/rods? Water Pump? The guy I got the boat from says he had it serviced by a local shop before it was stored and it ran fine at that time, so I wouldn't expect the bottom end to be blown up.

Thanks!

tashasdaddy · Feb 24, 2007

Re: OMC Sea Drive locked up

keep putting the oil to it, and keep working it. some times it takes quite a bit to break them free. then inspect the cylinder real well. they may have to be honed, and new rings. put in neutral and see if you can turn the prop. if the lower had water in it, it could be siezed.

Solittle · Feb 24, 2007

Re: OMC Sea Drive locked up

Use Marvel Mystery oil instead of crankcase oil, have lots of patience and don't rush it.

For what it is worth my 1987 1.6L V4 crossflow Seadrives (with the bubble back) are rated by OMC at 110 hp.

Tiderunner18 · Feb 24, 2007

Re: OMC Sea Drive locked up

The prop spins freely in neutral. I'll keep soaking the piston rings and see what happens. Thanks for the tips!

mikesea · Feb 25, 2007

Re: OMC Sea Drive locked up

if it hasnt been run in 10 yrs.you need to change the impeller ,so drop the lower unit ,this will allow you to move the flywheel back and forth,by turning it back with waterpump connected,you can damage the pump assy,also it will put additional force on your turning,

Tiderunner18 · Feb 25, 2007

Re: OMC Sea Drive locked up

I messed around with it a little more today and I'm pretty sure it's not the rings causing my problem. Something seems to be locked external to the engine. I started unbolting the lower unit but decided I should wait until my repair manual arrives before I go much further. I've been turning wrenches for years but have never worked on an outboard so I guess I should have some patience and read directions before I screw things up even worse.

How much oil should there be in the lower unit? When I drained it, I only got around 1 1/2 cups. The oil did look very clean, though.

mikesea · Feb 25, 2007

Re: OMC Sea Drive locked up

should have been a bit more than that,but if it was clean ,I would think all is ok.If your good turning wrenches,I'd bet the removal is not a challange to you.Be sure to get all the bolts,especially the shift shaft pin ,under the bottom carb,a 1/4 in ratchet,long extension and 3/8 flexhead socket make easy work,but i'm sue you cann figure it out.Might be easier to remove the cables from the engine for room( shift and throttle)Look for the 2 bolts by the trim tab that are also mounting bolts,one is under the tab so tab needs to come off,i have found some down here in Fl.Keys that have been left out by someone cutting corners or snapped off bolts.Its not rocket science .another possibility of the lock up.you might have a flywheel magnet that popped off and is lodged under the flywheel,there was one posted this week,the magnets are epoxied in place,but very common for them to come loose,flywheel removal is nec.to fix,good luck

Tiderunner18 · Feb 26, 2007

Re: OMC Sea Drive locked up

Well, after reading your post I decided to continue with removing the lower unit. I'm looking at the top of the shift rod and it looks like the head might be snapped off of the shift rod pin. There should be a 3/8" bolt head on the port side of the shift rod lever, right? Hopefully I'm just looking at the wrong thing since drilling that sucker out doesn't look like much fun. Looking at the Evinrude cyl & crankcase diagrams, it's bolt #33 that seems to be missing it's head.

DHPMARINE · Feb 26, 2007

Re: OMC Sea Drive locked up

Look at the starboard side,as well.I don't have Seadrive parts books,but Evinrude/Johnson V4's had the screw in from either side depending on the year.That Seadrive powerhead maybe an earlier or later model than the Evinrude you are looking at.

DHP

mikesea · Feb 27, 2007

Re: OMC Sea Drive locked up

agree with fact of bolt might thread from either side,.However,if the bolt is snapped,the piece is bolted to the linkage and can be changed,but still connected to shift shaft will be another problem,take it on one job at a time.

Solittle · Feb 27, 2007

Re: OMC Sea Drive locked up

On my 87s the head of the shift rod bolt is accessed from the starboard side - a pain to get out.

Tiderunner18 · Feb 27, 2007

Re: OMC Sea Drive locked up

I took another look at it today and it does appear the bolt head is snapped off. I was planning on rebuilding the carbs anyway, so I think I'll remove them and hopefully figure out a solution with a little more room to work. If all else fails I'll just cut the shift rod and replace it later, assuming that a replacement is still available.

mikesea · Feb 28, 2007

Re: OMC Sea Drive locked up

you might be able to cut the shifter piece off with a dremal tool,with small cutting blade or drill bits.that part is alum I believe so it should not be to hard.I would save the shaft,the seadrives have a little different bend in them and doubt many are around,a standard shaft could bre used,but you got to fool around getting a good bend that makes an offset,been there done that,with carbs off,a couple good tools and you will be back in business

Tiderunner18 · Mar 8, 2007

Re: OMC Sea Drive locked up

Quick update...

With the removal of the carbs and some careful use of a sawzall, I managed to cut the shift lever without damaging the shift rod. Removed the lower unit but the engine was still locked up.

After fighting a few stuck and broken bolts, I managed to remove the powerhead and tear it down. Turns out that the lower main bearing failed in a big big way and chunks of the inner race punched two holes in the case where the counterweight spins. I should be able to weld up the holes fairly easily and if the crank checks out ok, I just might have a rebuildable engine. Are lower main bearing failures common on these engines?

Dhadley · Mar 9, 2007

Re: OMC Sea Drive locked up

Was there water on the top main too?

mikesea · Mar 9, 2007

Re: OMC Sea Drive locked up

yes,the bottom mains were natorious for failure due to the design of the seadrive,there tends to be a lot of water forced up ,what is also very common is the driveshaft rusting so badly into the crank you cant get it down,also,the crank splines are sucepitable to striping out too,the water rusts the splines of the crank,the driveshaft tends to be stronger since its a solid piece,I had a slight bump on a sand bottom with mine and it stripped the crank splines out like machine work,had to tear the engine down and slip a new crank in her.Bottom line,be sure to keep the splines lubed with a good waterproofed grease,triple guard I think is the name by OMC.I guess its a good idea to change the seals on those engines at some point,but its a high labor job as you now know,even worse in the salt water of Fl.The seadrives were a good idea in my opinion,too bad they didn't make them to stand up taller avoiding the flooding problems,i have seen more homemade extra wide cavitation plates,silicone injected in about every hole water could enter on those engines when I was working outboards late 80's early 90's,people can be very inventive. Sorry about the winded story,good luck.

Tiderunner18 · Mar 13, 2007

Re: OMC Sea Drive locked up

Finally got around to finishing disassembly this evening. Here's the summary...

1. Hole in block
2. Upper and Lower mains dead. Upper was very rusty.
3. Crank pitted on upper main surface due to rusty bearing. Probably not repairable.
4. Two wrist pin bearings feel rough. Rods likely bad too.

Basically, the engine is junk. Looks like my choices now are to pick up a reman powerhead or just get rid of the boat. I figure $2500 for a powerhead and at least another $500 in carb rebuild kits, water pump, etc. Sound about right? Of course, if the fuel pump or electrical are bad, that'll add to the bill.

:'(

Dhadley · Mar 14, 2007

Re: OMC Sea Drive locked up

That's classic water injestion. The real bummer is that it'll do it again and again if you don't change something. Just for some background, here's what happens;

Water is getting sprayed up toward the powerhead. One of the basic causes is the motor being mounted too low, which Sea Drivers were famous for. As that spray (mist) mixes with the incoming air it gets sucked into the airbox. Once in the airbox some gets sucked in the carb throats, some falls to the bottom of the box.

In the bottom of the box is a line going to the lower main. This is to drain off or burn any excess fuel in the box. The water goes to the bottom main and then gets pumped up to the top main via the reflow system. The reflow passages are those little channels cut where the fron half and the intake meet.

The water sits on these large mains and rusts over time. Sometimes in a very bad case, the top and bottom cylinder will get water too. Basically, the top and bottom have water and the motor gets "cleaner" as you go towards the center.

mikesea · Mar 14, 2007

Re: OMC Sea Drive locked up

If the hull is something that is nice and works for you,buy a bracket,and mount a standard outboarb on it.If the controls and cables are in good shape,look for an eng by omc.You can use the same coontros ,guages,and steering if its a cable type.I'm doin it now.I had a 1984 2.5 seadrive v.6.Got tired of the problems.But in my case the powerhead is excellent and the lowerunit. I can use the p'h and make a standard 150 if I get a mid section. But i'm tired of old s***.

Tiderunner18 · Mar 14, 2007

Re: OMC Sea Drive locked up

Ok, so the damage isn't necessarily from water getting in through the carbs but it's the water that settles into the bottom of the airbox. Makes sense. So, since raising the engine up isn't too easy of an option, what can I do? The first thing that pops into my mind is to seal off the upper cover and then run some sort of flexible fresh air hose in over the transom. Maybe like a 3-4" hydraulic hose that would handle flexing back and forth with the steering.

I have a line on a couple Sea Drives for pretty cheap. One is a runner but he wants to keep the gear box ($700). The other is a complete unit that currently won't start, but at least it isn't siezed up. Still working on a price for that one. Whichever one I end up with, I'm tempted to replace the upper and lower mains before I run it. Is it possible to replace these bearings without splitting the case? Obviously, I'd have to pull the powerhead to do the lower but now that I have done it once, it won't be too terrible of a job.

OMC Sea Drive locked up

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