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Tan, MerCruiser Certified Technician
Category: Boat
Satisfied Customers: 11050
Experience:  40 yrs. experience with complete engine repairs both inboard/outboard and MerCruiser Certified Technician.
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Ive had a new Bayliner 185 Bowrider with a Mercruiser 3.0L

Customer Question

I've had a new Bayliner 185 Bowrider with a Mercruiser 3.0L I/O for about 3 weeks. Last night on the lake, it seemed as if the transmission would kick out over about 3000 RPM. I also noticed that the speedometer stopped working. Any ideas?
Submitted: 6 years ago.
Category: Boat
Expert:  Tan replied 6 years ago.

Hi my name is Tan I will assist you.


When you say kick out of gear does the boat stop all forward motion or just slows down?


Can you shift in to forward or reverse or does the boat not move at all?


Please explain with as much detail as possible.


Does the speedometer read at all or intermittent?


Have you hit anything?


Could I get an engine serial number please?

Customer: replied 6 years ago.

It will stay in gear under approx. 3000 RPM. It comes out of gear, but will continue to run at higher RPMs. I can shift into both forward and reverse. Boat will run at slower speeds.


Speedometer worked just fine, until the transmission problem occurred. I don't believe we hit anything, but we were in some weeds. I did notice a very tiny ding on one of the prop blades.


Mercruiser 3.0L, 135 HP, serial #1A642693



Expert:  Tan replied 6 years ago.

If the engine rev's and the boat doesn't move. The prop hub is likely damaged and will not allow you to go over 3,000 rpm's.


Remove the prop and check the hub. This is the hub kit click here for you drive and prop. The black part will be cracked and damaged.


These are designed to absorb any kind of impact or running aground so you don't damage the drive.


The speedometer pick up is on the very front of the drive, you will find a very small hole that gets clogged up with debris use a small drill bit to clean the hole out. The hole is in the very front of the lower unit about 3 inches up from the nose of the lower unit.


Post back with questions.

Customer: replied 6 years ago.

Disassembled hub. Black part is completely intact.


Any other ideas?

Expert:  Tan replied 6 years ago.
With the prop installed shift the drive in to forward gear check the prop. Remove the drain plug on the gearcase check for metal or water in the gear lube. Does the prop lock when you turn to the left?
Customer: replied 6 years ago.



Prop locks when turning to the left in forward. It also locks when turning to the right in reverse. Gear lube looks clean.

Expert:  Tan replied 6 years ago.
Does the drive make any sound when you are running at 3,000 rpm's to indicate the drive is jumping out of gear? Once the drive is in gear the way the clutch dog is cut in a way that the more pressure that is applied the harder the gears mesh together preventing the drive from jumping out of gear. Does the engine rev when it jumps out of gear?
Customer: replied 6 years ago.

The only thing I noticed out of the ordinary when it jumps out of gear is that the oil pressure guage jumps up for an instant.


Yes, the motor continues to rev when it jumps out of gear. When I bring it down to a lower RPM, it re-engages.

Expert:  Tan replied 6 years ago.
This all points to the hub of the prop disengaging. Have you checked for cracks in the hub where the spline engages. If these 2 parts show any sign of cracking this will cause the prop to slip. If there is any signs of plastic gouging the hub is bad. The area in red have to slide together no slop. Please check this again. The only other way this drive can jump out of gear is for someone to pull the shift lever out of gear.