1990 Force 50 Slips out at high RPM

[Wetbehindears]

Hello, first time poster! Little background: 1990 17ft Bayliner with 1990 Force 50. Purchased from family, somewhat cared for at a charity price. Im meticulous on my vehicles, restored a few vehicles frame off, so somewhat mechanically inclined... but first time boat owner. Had the boat for 1 year, when "purchased" I had the impeller changed out by a local marina. I have followed the Selco book to the T with maintenance, but I have encountered my first problem Sunday. Problem: boat engages in forward and reverse with no problems.. no noise, and very smooth. BUT when getting close to WOT she slips out of gear. Engine revs way up. When I let off a little she goes back in. As the way a transmission would slip. I got home and drained the lower unit. No water, so shavings, pressure tested and holds. I have never pulled the lower unit, but read the manual and it seems easy enough. Its time for a new impeller anyway. The only problem with the manual is... once I get the lower unit off, what am I looking for with these symptoms, Are there any suggestions? I would love to be armed with info before starting.

 

[steelespike]

Re: 1990 Force 50 Slips out at high RPM

You may have a spun prop hub.Easy to check,pull prop and mark the hub with an indelable marker so you can tell after a test if it slips.A prop shop can usually replace the hub.<br /> Just a little tip Be sure your motor idles as low as possible and when you shift do it crisply<br />but smoothly.don't drag it slowly into gear nor jam it into gear.If you study the gearcase you will see the forward and reverse gears and the clutch dog that ingages them when you shift.<br /> Sounds like you have been shifting correctly so far.

 

[roscoe]

Re: 1990 Force 50 Slips out at high RPM

Welcome WBE.<br /><br />I think you have an easier problem to fix, than you may think.<br /><br />If the gearcase was popping in and out of gear, you would hear it.<br />There is no clutch, just 2 large cogs that lock up.<br /><br />I think your prop hub is wore out.<br />What is a prop hub?<br /><br />The propeller is made up of an inner metal hub, and an outer metal housing, with a rubber bushing pressed between then to hold them together.<br /><br />When the prop hits something in the water, the hub is supposed to slip, theoretically to prevent damage to the drivetrain, kind of eases the shock.<br /><br />Sometimes the hub will just get wore out, from age or on your particular motor from hard acceleration. It is a common problem.<br /><br />If you have a spare prop, put it on and take it for a test run.<br /><br />Or, you can scribe a light line from the inner hub, across to the outer hub. Take it for a drive, allow it to "slip". Then take a look at the line you scribed. If the hub is "spun", the scribe line will no longer line up.<br /><br />You can take the prop to a prop shop or marina to have a new rubber hub installed, or you can buy a new prop.<br /><br />Check it out and get back to us.

 

[Wetbehindears]

Re: 1990 Force 50 Slips out at high RPM

Hmmm.. Never even considered that, however that does make sense! I have my Selco book with me right now and after reading the section Propeller. I see there are two different Propellers on these models. One is a COTTER PIN model and the other is a THRUST WASHER. Do both of these types have the rubber in the middle? I know my question would answer itself when I get home and pull the prop, but by looking at the book I cant tell. I have the Cotter Pin! <br />Thanks, and YES I will follow up with the results!

 

[roscoe]

Re: 1990 Force 50 Slips out at high RPM

Yes, both should have the rubber hub.

 

[Wetbehindears]

Re: 1990 Force 50 Slips out at high RPM

Followup:<br />THANKS ROSCOE!!!! It was exactly as you suspected. I scribed the inner and outter hubs and took it on a test run. As soon as it "slipped" I headed back to the dock. Lines no longer matched! <br />WELL... I have another question about the Prop, so I will start a new thread and see what you think! THANKS AGAIN!!!!!

 

[mercer57]

Re: 1990 Force 50 Slips out at high RPM

Just wanted to tell everyone who has this problem, If you put you motor in gear and spin the prop over a couple of good time by hand, if the hub is spun the scribed line will move, this is how i did it saved me time and money going to the lake to test, just my 2 cents.