Boat Randomly Sluggish

BlueBaron

Cadet
Joined
Jan 29, 2021
Messages
9
I have a Sea Ray 185 with a Mercruiser Engine. New Propeller and New hub. The boat randomly has trouble moving. Boat will move at a very low speed, but when I give it power, the propeller spins, but the boat wont increase speed. Cant figure out why this is happening. Problem is intermittent. Boat worked perfectly for years, but this is a new problem that was not corrected with a replacement prop and hub. Thanks for your help!
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,520
What brand of Prop and Hub? Does the prop have the same diameter Hub as the old prop? The I/Os use the same props that fit the Larger Outboards, however the Props for the midrange HP models will fit, but having a smaller Hub will have excessive Ventilation and resulting slippage

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BlueBaron

Cadet
Joined
Jan 29, 2021
Messages
9
The propeller is a mercury marine sports series black max. I believe the hub and the propeller are identical to what was there previously. And I had the problem before I changed the propeller. Thank you so much for your help.
 

jimmbo

Supreme Mariner
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May 24, 2004
Messages
13,520
How long have you owned this boat? How long has this condition been happening?
 

tpenfield

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Jul 18, 2011
Messages
18,104
We all tend to gain weight as we age, and I'm wondering if the boat has done the same? :unsure:

What you described is cavitation, which means the propeller is creating such low pressure on the back of the blades that the water turns into a gas (air) and the prop looses its grip.

If the boat and propeller are not a good match (too much pitch) cavitation will tend to happen. Less pitch can solve the problem, but it may be a 'band-aid' on a different problem (weight).
 

Bondo

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Apr 17, 2002
Messages
71,012
I have a Sea Ray 185 with a Mercruiser Engine. New Propeller and New hub. The boat randomly has trouble moving. Boat will move at a very low speed, but when I give it power, the propeller spins, but the boat wont increase speed. Cant figure out why this is happening. Problem is intermittent. Boat worked perfectly for years, but this is a new problem that was not corrected with a replacement prop and hub. Thanks for your help!
Ayuh,..... Do you boat in weedy water,..??
 
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