View Full Version : No power
SeaAngell
11-03-2007, 06:55 PM
its a 71 omc. we have done everything we can, still only 9.8 mph. so today someone asked me what the plug in the out drive was. I didn't know, looks like maybe the exhaust ? so tomorrow we are taking it back for test drive.
anyone know anything about older omc's
fishkisser
11-03-2007, 07:40 PM
You need to give more details on what you have, and what you have tried so far ... What problems are you having exactly ????:)
its a 71 omc. we have done everything we can, still only 9.8 mph. so today someone asked me what the plug in the out drive was. I didn't know, looks like maybe the exhaust ? so tomorrow we are taking it back for test drive.
anyone know anything about older omc's
We'll need some history and details on this one.
SeaAngell
11-04-2007, 09:10 PM
My Grandfather had the 305 6 cyl. engine rebuilt, then had a stroke. the boat sat for 15 years under a car port.
Once I got it, I had the outdrive rebuilt by Steve Ryan, new tilt motor, new fuel pump, carb rebuild, all new fuel hoses, altenator, new steering cables, cleaned out the fuel tanks,
It tacs out at 3500 and only goes 9.8 mph. Thats it. Its a big boat. 22' reinell, deep V w/cuddy.
We are stumped, had afew old boat guys in it today, thery couldn't believe how she runs, great but slow. They think the engine is just too small to push that boat.
It runs really good. Looks like crap but runs good LOL.
I'd really like to hear what you guys think.
We'll need some history and details on this one.
fish_on
11-04-2007, 10:18 PM
Could be the prop has spun on the hub, you are spinning the shaft but the prop is barley turning. At 3500 rpm it should be moving pretty good, just make sure that power is transferring to the prop.
fishkisser
11-04-2007, 10:34 PM
Could be the prop has spun on the hub, you are spinning the shaft but the prop is barley turning. At 3500 rpm it should be moving pretty good, just make sure that power is transferring to the prop.
That would do it huh... How does the prop turn in nuetral it sounds like gear bind to me on your lower unit ... is it an electric shift or linkage ...
My Grandfather had the 305 6 cyl. engine rebuilt, then had a stroke. the boat sat for 15 years under a car port.
Once I got it, I had the outdrive rebuilt by Steve Ryan, new tilt motor, new fuel pump, carb rebuild, all new fuel hoses, altenator, new steering cables, cleaned out the fuel tanks,
It tacs out at 3500 and only goes 9.8 mph. Thats it. Its a big boat. 22' reinell, deep V w/cuddy.
We are stumped, had afew old boat guys in it today, thery couldn't believe how she runs, great but slow. They think the engine is just too small to push that boat.
It runs really good. Looks like crap but runs good LOL.
I'd really like to hear what you guys think.
A 305 running at 3500 RPM is plenty to push that boat. My 10 ton rental 50' houseboats made about 12 knots with a 140 HP, 4 cyl OMC. Something is slipping and my first guess is the prop hub. Try a different prop. You should be able to "try out" a new prop from a dealer if you make it clear you're in the market for a new one.
The other thing to look at is what size and pitch is the prop. Should be something like 11"-13" diameter and 15-17 pitch. Also, measure the prop to make sure it matches what's marked on it. I have seen blades that have been munched and then "repaired" by grinding them down to reshape them.
What kind of outdrive is it? How crisply does it shift? I don't believe it's clutches slipping. The design of most outdrive clutches doesn't allow clutch slippage like you might get on a car. They usually either thump pretty obviously or fail completely.
On the other hand, I have seen EXACTLY your symptoms on several boats
with a slipping prop hub. It's a pressed-in rubber bushing inside the prop that is meant to absorb shock when the rotating prop hits a log or rock, and prevent damage to the prop shaft and gears.
One good alternative to a new prop would be a prop rebuilder. Ask around or look in the yellow pages or on line.
HntnFsh
11-05-2007, 02:26 PM
Could he put the drive in gear with the motor off.And turn the prop by hand to see if its spun?
Just a thought.
goodkarma
11-05-2007, 02:38 PM
unhook it from the trailer :laugh:
Could he put the drive in gear with the motor off.And turn the prop by hand to see if its spun?
Just a thought.
If it's really, really bad he might be able to move the prop on the hub, but probably not. The brass or stainless prop spline bushing is pressed into the rubber bushing, then the rubber bushing is pressed into the prop hub. There's really nothing holding all of it together but the compression of the rubber bushing. If it's slipping bad enough to turn by hand I doubt he'd be getting even 8 or 9 knots.
SeaAngell
11-17-2007, 03:07 PM
unhook it from the trailer :laugh:
I was laughing at that joke:laugh: while I was writing the orginal email LOL
SeaAngell
11-17-2007, 03:09 PM
its an electric shift.
have tried a different prop, didn't seem to make a difference
That would do it huh... How does the prop turn in nuetral it sounds like gear bind to me on your lower unit ... is it an electric shift or linkage ...
fishkisser
11-17-2007, 08:10 PM
Could be the clutch coil or a stripped water pump shaft on the lower end ... the pinion gears were notorious for stripping out also ... Hope this helps ...Barney
its an electric shift.
have tried a different prop, didn't seem to make a difference
If you tried a known good prop then you've eliminated the easy, inexpensive fix. Most likely the locating tang on the electric clutch has broken off (shifting under throttle will cause this). The thing is they usually fail completely and not just partially like yours. You'll need to take a close look at the lower unit "innards". Be prepared to buy some spendy parts.