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Cavitatin Aerating Prop slipping

J

john_oneal

New member
I have a 16ft/50" Alumawel

I have a 16ft/50" Alumaweld with a 30hp(1986) Johnson on it . The problem I am experiencing is as the boat accelerates and the effort to push the boat faster increases I suddenly lose forward propulsion. I have to allow the boat to slow almost to a stop then take off again . This condition seems to be getting worse with use and is compounded with increased load in the boat. The transom hgt. is 16" and the prop center line is at 23" it has a 10" prop with 3 blades. The motor cavitation plate is located at the level of the bottom of the boat. It feels like a car that has a clutch slipping . Does any body out there have any thoughts or suggestions on this problem . Your input will be greatly appreciated.
 
"Check for a slipping hub by m

"Check for a slipping hub by marking the hub and propeller with magic marker, then run the rig. After running, check the marks you made. If they moved and are now out of line, the hub is slipping.

You can also (with the spark plugs removed), have the engine in gear, jam the propeller with a piece of wood, the with a long breaker bar and socket on the flywheel nut, attempt to turn the flywheel/crankshaft. If the flywheel turns (and also the prop nut/propshaft), obvious;y thee hub is slipping.

When time permits, visit my store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"I have almost the same proble

"I have almost the same problem with mine. I have a 16ft all weld alum. flat bottom with a 25hp. It planes out quickly and the front digs in too far at high speed so I trimmed it up, but it started to "burn out". It fixed the front problem. Lowering it back down fixes the "burn out" but I have to run at a slower speed to keep the front fron pushing the water."
 
"To me it looks a bit like a b

"To me it looks a bit like a boat problem. Lifting up the boats and having a look at the bottoms, I would guess they have a negative hook. This works like a trim-tab: The higher the speed, the more the stern will lift/bow down and finally the prop gets lifted almost out of water. On alu boats this is very difficult to correct as the only way is 'to press' down the bottom from the inside. The only solution might be to try the 4-blade prop originally made for the 3-cyl 35, or 'modify' the excisting prop with a cup."
 
"I had mine upside down recent

"I had mine upside down recently and did notice right before the transom, there is a dip toward the inside of the boat. I this the hook you are talking about?"
 
Some pics on the boat from bot

Some pics on the boat from both inside and outside (bottom up) might give me an idea how to 'fix'. Nothing is impossible.
 
"all I have at the moment the

"all I have at the moment the other one coming next
147261.jpg
"
 
"Slightly difficult to get an

"Slightly difficult to get an exact idea due to angles, but that engine (gear housing) should gave the cavitation plate 1" BELOW transom."
 
"I maybe right at or a little

"I maybe right at or a little higher, its in tank at the moment to I cannot look at it."
 
"k komula............

(

"k komula............

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I apologize John O. I didn&#39

I apologize John O. I didn't mean to run over your post. I started out thinking I had the same problem and got carried away. Sorry. I hope you get the answers you need. KK
 
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