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help - Yamaha 4hp 2 stroke (4 SG)

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palmerbr

New member
Folks - have a 1989 4hp 2stroke that's run fine for several years, but 'froze' at the end of this season ... went to check/change water pump impeller, couldn't get lower assembly off without some 'force' ... turns out drive shaft is stuck solid in top unit ... any advice on how to remove ?... already need a new drive shaft (from my 'persuasion), so i'll be approaching the value of engine if i need much more - but, has been a great little engine, i'd like to keep it running.... advice???
 
Do you have the lower gearcase off, and if so did you rip everthing out through the waterpump or did you cut the shaft with a sawzall? You did disconnect the shift linkage?? The shaft will be frozen in the end of crankshaft. Turn the motor upside down and spray a good penetrating oil, but make sure it won't harm rubber onto the shaft and let it run down to the crankshaft. Let it sit overnight. In the meantime, round up a length of 3/8 chain 10 - 15ft and and two good pairs of vicegrips. The next day wrap the chain up the driveshaft and clamp it tightly to the shaft as far up.as you can with the first pair of vicegrips. Clamp the second pair of vicegrips onto the shaft as tightly as you can and tightly against the wrapped chain. Now you need to position the engine so that it doesn't move, or if it does move, not much. How you do this is at your discretion. I have laid them on a tarp and sandbagged it into position with the chain coming through the first layer of sandbags. Lay the chain out in line with the shaft. Now lift the loose end of the chain up so that a loop is formed, and lift the chain up and snap it down like cracking a whip. It acts like a poor mans slide hammer and should yank the shaft out.
 
Bumper food ... Thanks for the help ... Yes, I did disconnect shift linkage, and yes I did rip everything out through the water pump ... I've already got it hanging from a rafter by the shaft, I'll try the penetrating oil/chain trick you suggested this week, I'll let you know....any recommendations on oil??... Thanks again
 
The only reason I would use a penetrating oil that does not have an effect on rubber is the offhand chance that it may find its way onto some seals in the engine, causing them to swell and leak- not likely but I would not like to exacerbate the problem you already have. I have used LPS but it is more of a moisture repellent. You need to weigh the benefits of a good penetrating oil against the possibility of more damage.

Unfortunately, now you have to pull the lower drive unit apart, to check for damage, certainly the waterpump, and lower shaft seals, will need replacing as well as any bushing etc. You probably have not damaged the pinion, but there will be pieces in the gear housing that will need to be removed and replaced. Providing you can get the shaft out of the head without any more damage, I think you should consider getting a used lower housing, such as this one on e-bay http://www.ebay.com/itm/8hp-Yamaha-..._Accessories_Gear&vxp=mtr&hash=item415f6e04b7 I am in no way affiliated with this seller.
 
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