1998 Merc 25hp...Motor rev during weed excursion

[JimInMichigan]

Took the 1998 Smokercraft 14/68 with a 25hp Merc that I am thinking of buying off my cousin.

While out testing the boat/motor in Houghton Lake ( Mi. ) we ended up in either a Milfoil or Hydrilla patch. I slowed down as soon as I seen some weeds floating. When I tried to throttle it up, the motor started to free spin, like I was rev the motor in neutral. I could run about 3-5 mph, but as soon as I got on the throttle, neutral rev again. I stopped the motor and checked the prop. No weeds around the prop, but a huge clump between the transom and motor shaft. I removed them and tried again. Same results until I got out of the patch.

Is this normal or is there a problem with the motor? Is there some kind of clutch that let the motor loose when the prop was overloaded in the weeds? I'm totally new to boating with a gas motor. I thought the prop would just act like a salad shooter and mince those weeds!

 

[turbotodd]

I've had similar issues on a local lake that is FULL of the stuff (underwater grass). I think what happens is that the stuff gets wrapped around the prop and as soon as you stop it falls off. That's been my experience for the most part. I hate the stuff for that reason; but bass love it.

 

[PatinIdaho]

Has happened to me also. Been so bad my gas engine would not go forward at all, just sit there and rev up. Had to raise it and use the minkota TM to get out of it.

 

[JimInMichigan]

IN either of your experiences, did it seem like you were in neutral while reving the motor? Mine started pushing the boat then just seem to jump into neutral when I gunned it.

I just read in another thread ( the guy buying an ebay prop and was asking about painting it ), and he talked about the prop repair guy telling him to make sure the hub didn't slip with the new prop. Wondering if I had some hub slippage going on.

Once out of the weeds it did seem fine, but I was close to the boat landing and didn't was to chance getting too far and having the motor quit working. So I didn't test it further.

 

[JMichael]

I'm betting that it was just a mass of weeds caught on the foot. I get the same thing all the time on a local lake. When it gets so bad that I'm barely moving, I stop, put it in reverse and back up a few feet, turn the motor enough that it will miss the clump of grass that I just got free of, then go again until the grass builds up again. You really need to keep an eye on the tell tale stream to make sure you don't overheat your engine doing this. Sometimes the grass is bad enough that it will restrict the water pump intake.

 

[Natedog57]

JimInMichigan » 08 Aug 2014, 19:17[/url]"]I stopped the motor and checked the prop. No weeds around the prop, but a huge clump between the transom and motor shaft. I removed them and tried again. Same results until I got out of the patch.

Weeds/grass can add a tremendous amount of resistance, and they can be quite heavy. Your prop is designed to push a certain load, once that load is exceeded the prop has a difficult time keeping its "grip" on the water, and it "blows out" or cavitates if you accelerate too quickly. The weeds themselves can also tangle and wrap up the prop.

When running in weedy areas it's also a good idea to carry a piece of small diameter wire to help keep the tell-tale passage clean.

To check for a spun hub on the trailer: put the engine in gear and try to spin the prop backwards.

 

[richg99]

While you are checking for a possible "spun hub", you might want to pull the plug wires and be certain they are clear of any possibility of igniting the spark plug. Chances are slim that she would power up, but no sense in taking any risk.

 

[waterman]

Cavitation.

 

[onthewater102]

Spun hubs don't magically fix themselves when you get out of the weeds.