'79 Mercury 900 outboard power loss

[talbee]

When going back to shore my engine powered down, then revved high. Though I got back to the dock, it felt like the exhaust was the only power I had to get me back to the dock.

I'm really hoping my lower unit didn't just go out.

I would like other thoughts please.

 

[jimmbo]

Need more info than just

When going back to shore my engine powered down, then revved high. Though I got back to the dock, it felt like the exhaust was the only power I had to get me back to the dock.

I'm really hoping my lower unit didn't just go out.

Do you have forward, neutral, reverse?
Can the engine accelerate?
Does it run rough?

 

[talbee]

I can go forward and neutral, but I've not tried reverse.

When I go forward it moves the boat at a slow speed. When i try to go any faster it's like it kicks out gear and revs really high like when you rev the engine in neutral.

It doesn't run rough.

 

[Chris1956]

It could be a spun prop or bad gearcase. What does the gear oil look like? Any metal on the drain screw?

 

[talbee]

I haven't had a chance to take a look at anything yet because of my work schedule. I just needed a general idea where to start. If it is the gear case, how much is that gonna run?

 

[talbee]

I just got back from running the boat on the river and i can see the propeller rotate when i put ot in forward and reverse, but it's still doing the same thing

 

[talbee]

It could be a spun prop or bad gearcase. What does the gear oil look like? Any metal on the drain screw?

Gear grease is black and i dont see antetal fragments

 

[Chris1956]

Well, black is not a good color, but not to panic yet. Remove prop and mark brass prop hub and aluminum prop with matching marks. Reinstall and run her in the lake. If the match marks no longer line up, have prop rehubbed. Change the gear oil as well.

 

[talbee]

I'm sorry Chris, I'm not sure hat you're talking about. Any pics? This is my first boat. Also, what weight of gear oil do I use?

If it needs rehubbed, we don't have a shop in our area that works on older motors. They only work on '85-newer

 

[jimmbo]

Any prop repair shop can rehub the prop. For gear lube, use the 'High Performance gear lube https://www.mercurymarine.com/en/us/...nts/gear-lube/

 

[surfsalterpath]

......i had the same problem a few years back and I was totally perplexed also. As jimmbo suggests remove the prop and carry to any prop shop get it rehubbed. Easy as that. I think it cost about $60.