Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

[citadel1995]

I have a 96 Yamaha Saltwater series 150hp. Was running great, shifting with no problems. Was going about 4500rpms when canopy railing flew up & snapped so I pulled throttle back fast, when everything was tied back down I gave it gas and the motor went into gear but when I hit throttle the motor revs up but the prop starts slipping. The motor goes into forward & Reverse with no problem, and as long as it stays under 1200-1500 rpms the prop spins and works as usual. but once more throttle is given the motor revs up but nothing from the prop. I got home, and with the motor off put it in gear and tried to spin the prop by hand and applying some force it turns the drive shaft and motor with no slip, in both forward & reverse. I drained the lower unit and the oil was milky (I changed it this year) and there were some metal shaving on the drain plug magnet. Any advise on what I should check or do first? How can I tell if it the prop Hub or the gears with out taking it all apart?

Thanks for any help!!

 

[BaileysBoat]

Re: Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

Probably a spun prop hub. A small amount of mteal on the lower fill screw magnet is normal. Milky oil means a gear case leak. Did you replace the drain/vent gaskets when you last serviced the L/U?

 

[citadel1995]

Re: Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

no, I didn't replace gasket for the drain & vent screws. Something I didn't think about when I was changing the oil. How can I check the prop hub? or is it best to just replace the prop and see if it does the same thing with a new prop?

Thanks!

 

[99yam40]

Re: Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

Mark the hub and the prop , run it and the see if the marks are still lined up

 

[robert graham]

Re: Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

Sounds like a spun prop, you can have it rebuilt at a prop shop and/or buy a new prop. The water in your gearcase is a different problem, maybe bad drain/fill washers/gaskets, prop shaft seals, driveshaft seals, shifter shaft seals. When you remove prop, check propshaft seal for fishing line wrapped around causing leakage/damage to that seal. Good Luck!

 

[citadel1995]

Re: Need Help Trouble Shooting 1996 Yamaha 150hp Lower Unit

Thanks guys! It's a spun hub! I marked the hub & prop took it to the ramp today. The hub marking moved. I never thought about the hub since I was in deep water, there was nothing wrapped around the shaft, and the reason why I had stopped was because I pulled pulled the throttle. I was so worried about having to tear apart the lower the lower unit I overlooked the obvious. The prop is 15yrs old but in excellent condition, it's a Stiletto that came with the motor when my father purchased it in 1996, he never used the boat only put 50hrs on it, so it looks pretty much new. Is this prop repairable? is it one that must be done by a prop shop or can I get the parts & do it myself?

The milky oil in the lower unit I think is because I didn't change the gaskets on the fill/vent screws when I changed the oil this season, the old oil from last year looked good when I drained it so I know it wasn't leaking until I messed with it. Thankfully I really haven't been able to fish that much so I haven't used the boat but a few times this year. I read somewhere a suggestion to pressurize the lower unit and see if there are any leaks, has any body tried this or heard of this? Is this a good or bad idea? How much pressure should be applied so that the gaskets/seals aren't blown out 5-10psi? I've done plenty of leak down tests on motors before, sounds like this is pretty much the same thing. Any suggestions here?

Thanks again! You guys helped me allot last year when I had to rebuild the carbs and again now!!