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Jason
Jason, Marine Mechanic
Category: Marine Electronics
Satisfied Customers: 506
Experience:  Degree in Marine Technology, Also Certified with Mercury Marine, MCM, MIE, VP, Yamaha, Honda, Suzuki
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I have a brand new 1650 superhawk with a 90hp merc when i try

Customer Question

i have a brand new 1650 superhawk with a 90hp merc when i try yo get on plane motar rpms get to about 5000 and then boat feels like it goes into nuetral and slows down and rpms go up
Submitted: 1 year ago.
Category: Marine Electronics
Expert:  Tan replied 1 year ago.
Hello. My name is***** the prop and the prop shaft with a permanent marker straight. Now run the boat do the lines line up? Here is an exapmple of how to mark the prop and prop shaft. http://i.imgur.com/1fiQyTF.jpg
Customer: replied 1 year ago.
yes they line up
Expert:  Tan replied 1 year ago.
Did you run the boat in gear under load boating acting up?
Customer: replied 1 year ago.
when i try and accelerate rpms shoot up to 5000. boat starts to plane out than acts like its in neutral and revs rpms higher but wont go anywhere with no alarms
Customer: replied 1 year ago.
if i let off throttle i can feel motar go back in gear at lower rpm as soon as i try and accelerate slow or fast it does it again
Expert:  Tan replied 1 year ago.
I understand that but after you marked the prop did you take the boat back out for a run? Then check the marks do they line up. What your symptoms are telling me is the hub in your prop is spun allowing the prop to slip and not get traction in the water. These props have a sacrificial hub that will slip keeping you from damaging the gearcase.
Customer: replied 1 year ago.
no i have not
Customer: replied 1 year ago.
what would cause this i have only taken boat out twice and didnt hit anything
Expert:  Tan replied 1 year ago.
Ok you have to run the boat to see if the hub is spun. You could just pull the prop off and inspect the hub. Depending on the type hub it will be either cracked or you will see rubber peeling out the back of the prop. If you aren't sure post some pictures and I can tell you.
Customer: replied 1 year ago.
ok ill check hub
Expert:  Tan replied 1 year ago.
Let me know. This is about the only problem you can have on a new boat. Why the hub spun is hard to say. Heavy loads can cause a hub to spin. Loose prop and a soft impact can cause.
Customer: replied 1 year ago.
hub is like brand new no cracks or anything wrong
Expert:  Tan replied 1 year ago.
Do you have all these components in the hub? http://www.westmarine.com/buy/mercury-marine--flo-torq-ii-hub-kits-and-components--P006_190_002_541 Ok then the only thing left is the shift cable isn't adjusted correctly and the engine isn't going into gear all the way. Remove the engine cowling now have a friend shift the engine into forward gear. Now with prop back on turn the prop to the left CCW does it lock in gear?
Customer: replied 1 year ago.
yes i have all the parts and yes it locks in gear all the way i think how can you tell it makes clicking noise and prop stops moving
Expert:  Tan replied 1 year ago.
When you spin the prop one way it will click if you spin it the other way it should lock. The prop should lock when turning to the left CCW in forward and lock to the right CW when in reverse. Do you have the motor trimmed all the way down when getting on plane?
Customer: replied 1 year ago.
yes tried with trim all the way down and with it up at level
Expert:  Tan replied 1 year ago.
Is the engine actually revving or are you relying on the tach? Are you sure there are no cracks in the black plastic hub? We need to do the prop test with the marked line through prop shaft and prop. http://i.imgur.com/1fiQyTF.jpg
Customer: replied 1 year ago.
no i can here rpms rev up i can tell prop stops spinning and motar revs up and starts to back fire untill i back off throttle and then i can feel it go back in gear
Customer: replied 1 year ago.
and yes no cracks in hub
Expert:  Tan replied 1 year ago.
These are all symptoms of a bad prop hub. If this were an older motor it could be the driveshaft splines in the crank shaft. The engine is to new for that. So it isn't going into gear or the hub of the prop is bad. Take the boat out for a run. Disconnect the shift cable on the engine and shift the motor manually. Does it still slip? If yes then the prop is the only thing left.
Customer: replied 1 year ago.
ok i ll try that
Expert:  Tan replied 1 year ago.
Is there anything on the bottom of the boat that could be in the flow of water to the prop. Transducers can cause the prop to cavitate and loos propulsion.
Customer: replied 1 year ago.
All that is there is a transducer which is very small
Expert:  Tan replied 1 year ago.
Ok we are left with checking that the engine is shifting into gear manually and the prop.

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