Lost Power to Prop

S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Everything was going fine this weekend. Boat was running well until all of a sudden we lost power to prop. We were driving up on plane, probably about 3/4 throttle when we heard this noise (sounded like a hard shift at high throttle) and the motor revved up but no power to the prop. Got the boat out of the water and tried spinning the prop. spins one way in F, both in N, and no movement in R. On the water I thought it was a shifting problem but it appears to be shifting fine, just not getting any power to the prop. Motor starts up and revs fine. Any ideas? Thanks.
 
M

Maxz695

Guest
Re: Lost Power to Prop

The prop may have spun or the engine was cavitatng. Your descripton of the prop shaft is correct and so the LU should not be the likely issue Just my opinion
 
Silvertip

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: Lost Power to Prop

If you don't know what a spun hub is, it is a condition where the rubber cushion between the hub of the prop and the outer blade area breaks loose (the bond breaks). Under power this causes the hub to spin inside the blades which obviously causes loss of "push". You may or may not feel that by trying to turn the prop by hand. Place a mark on the hub and another mark on the outer blade area in line with the first mark. Then run the boat. Check the two marks. If they are no longer in line, the prob needs to be re-hubbed or replaced. If the marks are still in line there are other issues.
 
S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

Thanks. I'll try to check that out this week and I will let you know if that is the problem.
 
S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

Well its not a blown prop hub. I took the prop off and hooked the motor up to the muffs today. The prop shaft is not turning. Any other ideas? Thanks.
 
M

Maxz695

Guest
Re: Lost Power to Prop

Time to drop the LU the Drive shaft may hev busted if the prop isn,t turning.
 
C

CharlieB

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S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

Over the break I dropped the lower unit to take a look. Driveshaft looks fine but when turned the prop shaft does not move and there is some resistance on the drive shaft. Any suggestions at this point? I may just have to take the lower unit in to a marine mechanic and have them diagnose the issue. on the chance the the lower unit is totally blown has anyone had experience with some of the aftermarket lower units like SEI outboards. Outboards, Outboards, Sterndrive Engineering

Again the Motor is a 1997 90 hp Mercury 3 cyl. 2 stroke oil injected so I think I would need the SE205.
 
Bondo

Bondo

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Messages
71,097
Re: Lost Power to Prop

stuckinthehole said:
Over the break I dropped the lower unit to take a look. Driveshaft looks fine but when turned the prop shaft does not move and there is some resistance on the drive shaft. Any suggestions at this point? I may just have to take the lower unit in to a marine mechanic and have them diagnose the issue. on the chance the the lower unit is totally blown has anyone had experience with some of the aftermarket lower units like SEI outboards. Outboards, Outboards, Sterndrive Engineering

Again the Motor is a 1997 90 hp Mercury 3 cyl. 2 stroke oil injected so I think I would need the SE205.
Click to expand...

Ayuh,... Welcome Aboard,... Did ya shift the lower unit into gear,..?? forward,..?? reverse,..??

The resistance is probably just the impeller in it's housing....

What do the splines, at the top of the drive shaft look like,..??
How 'bout the splines in the bottom of the crank shaft it slides into,..??
 
S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

It is in forward right now. Spline at the top of the drive shaft look fine. I didnt look at the splines on the crank shaft but I will try to do that when I go back later this week. Thanks for the help.
 
S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

Drained the lower unit oil today and the magnet had 3 chunks and some shavings of metal on it so it looks like i busted a gear, probably at least the pinion gear. Also the oil was pitch black. I think that means there was exhaust leaking into the lower unit. That oil was changed less then a year ago and the boat hasn't been used much this year. I think I will start looking at the SEI lower units. I might pull into mine next weekend but it probably won't be cost effective to try to repair when I can buy a new one with 3 year warranty for around $1000. What would you guys do in this situation? The boat is going to have to sit for the winter until I can save up the money to do anything to it, so I have a few months to think about it.
 
M

mr 88

Commander
Joined
Nov 3, 2010
Messages
2,220
Re: Lost Power to Prop

If you have deep pockets [and you write that you do not] go for the new one. If you do it yourself it may cost you 50-200 depending on what gear or gears are broke. Buying new gears and seals from a dealer vs ebaying / napa is another cost variation.What do you have to lose by repairing it yourself,you can't make it any worse than it is now and you can buy that new one anytime you want if you throw the towel in.I would buy a manual or search it out here and do it myself.You said it is gonna sit,pull it off and take it down to your heated basement and get after it.Use that money you were going to drop on a new one for gas next season.........I think the black oil is a result of the gears being sheared and not the exhaust,if the oil was milky then you would have a seal failure as well
 
S

stuckinthehole

Seaman Apprentice
Joined
Aug 13, 2011
Messages
46
Re: Lost Power to Prop

Yah im going to take it apart next weekend and see how bad it is. I'll let you know how it goes.
 
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