Home Forums Hunting & Shooting Hunter's Campfire 1978 OMC 5.0 L Outdrive Help

I might buy a beater boat that has this unit. How hard are they to drain the water from the engine, and what problems do they pose...reliable??

You might want to try that question in the iboats forum for OMC drives.

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There has to be a video on utube that will show how to do that.

Try and find one... I looked all over for one, tried many key words...no luck.

I also struck out at iboats, so I thought I might try here. I do appreciate the replies.

I can’t believe there is no video. Did you try a boat repair shop? They should know?

Typing; "winterizing an inboard outboard" produced several hits for me. I didn't even know there were special kits..

I'd look for a old mercruiser over a omc. You can find parts for the merc.

Is it a Cobra? Or older than that?

This is a 5.7L but it should be similar.

https://www.youtube.com/watch?v=8vAKIxzkkC0

I had a 3.0L Mercruiser and it was pretty easy. Pull the drain plugs on the manifold, open the drain petcock on the block, Pour a little antifreeze in through the plug on the thermostat housing and call it good.

You should have a drain on each side of the block for a V8. Feeding in antifreeze through the water pickup like the youtube guy does is probably a good idea, but I never did that. Never had problems.


Jerry

I put stabilizer in gas tank, run motor, spray fogging oil in carb until it’s smoking good, kill motor, pull drain plugs on each side of block, call it good.

Safari, I would call a local marine junk dealer in older engines. Should be several close to you. If that failed I'd call the nearest Glastron boat dealer near you and ask for their oldest mechanic. They have used the OMC units for years. I know we handled them in 1978 when I worked for them when in college. powdr

Easy to drain but also very easy to miss a place or two and if they freeze can and will cause major problems.
make sure parts are still available for that year/ model. Merc is not very good at supporting older models part needs

Its your money but I would never buy an I/O. They can be a royal pain in the butt to maintain. Just a new seal between the hull and the outdrive runs into big $$$$$. Not to mention if the engine has problems. I'd always go with an outboard.

I don't know of your location but if there is any chance of them having seen a freeze I would be highly suspicious. Removing an I/O engine to replace the block from a freeze crack is not a process that I would describe as enjoyable. If the 5.0 is anything like my direct drive Malibu Skier with the 351W, there should be one large plug at the bottom of each manifold and a couple plugs on the block on each side. As stated, find a schematic and make sure all are pulled plus the water pump drained when left for winter storage. Gimbal bearings and bellows typically give problems with age on outdrive units. I cannot speak for the reliability of OMC outdrives as I only briefly owned a Merc outdrive.

I've owned seven boats with Mercruisers, and gimble bearings were the only bugaboo. The Bravos are a joke and HARD to completely drain. The 260 and Alpha series are easy to service in comparison.

I've never dealt with the OMC older or new Cobra units. This boat has the 1978 225 Stringer tilt, which is often a problem, but it can be set to a tilt angle and left there...doesn't help the hole shot, however.

Many days when I fish Pyramid or Topaz lakes the engine can freeze up before I make the drive back home if it's not drained. I checked out an older (1975 190 unit) I have on a "project" boat on the place, and I found drains, one on each engine side, and one on each manifold; both were easily accessed. The small block Ford engines probably all have the same drain locations, but I need to know that or whether there are more. Also, is there a water pump drain?

I do prefer the ease of an outboard simply being dropped all the way down to drain and the fact they can be left at moorage during hard freezes, while outdrives need draining if they don't have closed systems...except for the Merc Bravo units, which have to be drained at a spot hard to access UNDER the engine.

I've had no first hand, nor any second-hand knowledge of the quirks of the older 225 OMCs. There's not much on the internet, and I figure with the wealth of experience here someone would know.

Thanks everyone for the added replies.

You're correct about the drain locations being the same on your project boat and the slightly later OMC outdrives. I'd stay away from one if possible. I had a 1978 or 79 boat with 351 Ford and an OMC outdrive. Nearly lost the boat at the dock when the rubber boot around the outdrive developed a crack and water came in just a little faster than the bilge pump could handle. I got the boat on a trailer but it was a little heavier than normal by then.

The only time I'd buy an outdrive now is if the hull is good and worth installation of an outboard bracket and a newer four stroke outboard.

The older OMC outdrive units, prior to the Cobra system, are very poorly designed. The use of meshing ball gears to transfer power from engine to outdrive is a disaster. I can’t tell you how many we replaced back in the day. When you trim the unit underway, the gears begin to prematurely wear as the distance widens. Soon, the lobes on this ball gears are beginning to shear one another and will trash themselves. If I/o Mercruiser or Volvo. Engineering is sound. Maintenance on them is straightforward. When you winterize, remove prop and make certain no mono fishing line is wrapped into prop shaft seal. Water will displace lube and case can also freeze break. Real cheap insurance. Sounds like you’ve got plenty of sound advice on drain port locations. Good luck.

I suspected as much about the older OMCs, and the Cobras aren't all that great. I'm passing on the boat. I could get it VERY cheap, but sometimes free is anything but that.

Man this thread brings back memories. I had a 175 HP 1976 OMC. It was a good setup and much more reliable than the outboards of the time. It was new then, but well used when I sold it and solid as a rock.

Never had a problem with the meshing ball gears, not saying others didn't. OMC said not to give the engine much power when the foot is lifted because the ball gears aren't fully engaged and I didn't.

It wasn't hard to winterize at all. Pull the drain plugs out of the exhaust manifolds and tilt the engine, then lower the foot. Remove the prop and I was done.

A few things that caused me trouble over the ten years I had the boat....Your boat won't be exactly the same but it will be close.

I replaced the exhaust manifolds after about 6 years of salt water use, before I had a problem...They were rusted paper thin by then.

The tilt/trim was hydraulic and the water hose rubbed a hole in the hydraulic line dumping all the fluid into the bilge. Made the boat very difficult to steer, but it still got me home. I had to use a jack to get the engine high enough in the bilge to replace the line. Make sure the hydraulic line is clear!

Buy a hand full of ballast resistors and keep them on the boat. When it will start but won't stay started, when the ignition is switched to run from crank, change the resistor.

I did have a problem with the way the OMC transfers power from the vertical shaft to the horizontal shaft the prop is on. They use an electric arrangement to tighten a coil spring around the shaft. One spring for forward and one for reverse. Energize the forward motor and the forward spring tightens on the drive shaft, reverse tightens the reverse spring on the drive shaft. A momentary loss in power at cruse speed, shears the spring and from then on (until you replace it), it only goes in one direction. Need to check the electrical connections every year. They used a type of connector on the lines that control the shift motors that weren't very positive or permanent. I backed my 20 foot boat about 5 miles against an outgoing tide.

Mine had a 305 or 302 cubic inch engine. Don't remember which. It was a good engine and would run on gas that would stop an outboard. I saw that. Pulled the outboard back to the dock.

As much as I loved and trusted that old OMC, I wouldn't look at a brand new one today if they were to give it to me. Outboards are the only way to go around here. They are much more reliable than the old OMC and almost trouble free.