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1985 Yamaha 15 HP

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aniebla727

New member
I just got a basstender with a 1985 Yamaha 15 HP. When i bought the motor from a marine store the owner had told me that the engine was running perfectly fine. He even tested it out in a bucket and everyhting but its not the same as if were in the water. As soon as i out the motor into the water after around 5 minutes it feels like the motor has no power at all and it shuts off on me and right after it shuts off smoke comes out of were the water spits out of the motor. The motor turns back on but i do not know why it keeps shuting off. Also i noticed that some oil keeps spilling out of the lower unit which im sure its gear lube. Why would the oil just come out?

If anyone can help that would be great
Thank you in advanced
 
You may be overheating. Probably be a good idea to have the compression checked, service the waterpump and thermostat. Check/change the gearlube. Now you will be able to evaluate further without risking further or possible damage to the powerhead from overheating. If this is a saltwater motor be careful with fastener removal. Your motor is old enough to have corrosion around threads. Hopefully you just have something restricting your fuel flow but if that motor were mine I would want to know that the cooling system was sound before venturing out again.
 
I just checked the compression and both cylinders are at 120 psi. I do see oil coming out I the lower unit is that suppose to be like that?
 
Your compression is good. The oil coming out of the lower unit could be gear oil--really stinks and is thick, or possibly oil/fuel residue--black and thin. Removing the prop will help in the diagnosis if your not sure. If you have access to a compressor and a blowgun then low pressure air (5-10psi) in the top filler hole will often indicate the source of a leak.If you have steam coming out of the water pee hole then you are overheating. Remove the lower leg, and as PBRMAN says service the water pump, if you find that the impeller has broken up you will need to find all the bits and pieces. It is also possible that your thermostat needs replacing and I will second the forewarning about corroded fasteners.
 
bumperfood said:
Your compression is good. The oil coming out of the lower unit could be gear oil--really stinks and is thick, or possibly oil/fuel residue--black and thin. Removing the prop will help in the diagnosis if your not sure. If you have access to a compressor and a blowgun then low pressure air (5-10psi) in the top filler hole will often indicate the source of a leak.If you have steam coming out of the water pee hole then you are overheating. Remove the lower leg, and as PBRMAN says service the water pump, if you find that the impeller has broken up you will need to find all the bits and pieces. It is also possible that your thermostat needs replacing and I will second the forewarning about corroded fasteners.
Click to expand...

I do have steam coming out of the pee hole. I noticed that when it shut off when i was in the water white smoke will come out from the pee hole. I took of the lower unit and i check the water pump and it looked to be fine to me i did not find any chips of the impeller. Should i still change the water pump and the thermostat? I attached some pictures so you can tell me what you think. There is also one of the pictures that has a little orange thing is that suppose to stay thewre hanging or is it suppose to go somewere.
http://i446.photobucket.com/albums/qq189/Bo0sTeD4G63/oil.jpg
http://i446.photobucket.com/albums/qq189/Bo0sTeD4G63/lowerunitrod.jpg
http://i446.photobucket.com/albums/qq189/Bo0sTeD4G63/lowerunit.jpg
 
Dealing with the oil on the floor, IMO that is gearcase oil and you need to find the source of and repair the leak. As there is so much, it should be fairly obvious.

The water pump impeller, although it looks fine, should be replaced, the vanes should be pliable, and it appears they have taken a set.
A couple of points to consider about replacing the impeller. When turning the driveshaft, always turn it in the direction it would turn as if the engine were running, which is clockwise when viewed from above, paint a little arrow on the housing. The tube that carries the water up to the head, must be a fairly tight fit in the waterpump housing, if its too loose water that should be going up to the engine leaks by, resulting in an inadequate supply to the engine for cooling.
You may or may not have to replace the thermostat, but to check it you will have to remove it. It should be closed when you first remove it, Suspend it in a pot of water on a stove and heat it up, it should open around 130 or so degrees. Judging from the bolts that you removed from the waterpump, I don't think you will have a problem with corrosion, unless those were new bolts of course.
Looking at the picture of the shifter rod, you should of removed a cap and retaining screw, I don't see it, so this is just a guess. It may be that sometime in the past, someone stripped out the hole, and in order to keep the shifter in position has put a spacer that, holds it in position by taking up the gap between the boot and the section of the upper housing that the shift rod goes through. I will probably end up with egg on my face on this one though.
 
The last poster is guessing. The orange, originally white plastic retainer above the shift rod bellows is the piece which retains it. You failed to disconnect the shift rod coupling when pulling the gearcase. That stuff didn't need to come out, but now that it did I would replace the bellows with a new one. Then reassemble the parts into the gearcase. Apply #3 aviation permatex to the ribbed part of the bellows which inserts into the gearcase. Remove the self tapping screw from the top of the retainer piece and inspect it. If the retaing knobs are still intact you can reuse it. Push it down until the knobs engage the holes in the gearcase and then screw the screw in to spread the retainer.
Replace the impeller and gasket. Change the gearlube, it has water in it but it wouldn't hurt to run it a while and see if the problem is fixed with the new shift bellows.
When you insert the shiftfer into the gearcase hold the case with the prop shaft pointing down.
Grease the drive shaft spline and all fastener threads with marine grease. Make sure upper and lower shift rods are in the same phase before reconnecting the tall nut.
When this is all running again you are still going to need to diagnose the stalling problem.
 
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