25hp and 20 hp lower unit

[redogman67]

Hey everyone, I have a 1974 evinrude 25 hp that I am pretty sure has a bad clutch dog/and or forward gear. When driving on my boat it slips out of gear and feels like I am hitting things even though I am not. SO I am pretty sure the lower unit gears are shot. But I just got a free motor from a buddy that doesn't run. I think its a 1970, its a Johnson 20 hp model # 20r-70e. Anyways I am wondering if the lower unit from the 20 hp will fit onto my evinrude. And if so is it hard to do?

Thanks guys,

Dean

 

[elcamino12sec]

Re: 25hp and 20 hp lower unit

All you have to do is turn your clutch dog around. If you replace it with a new clutch dog it will start jumping out of gear after a week or two. The new clutch dogs are made for a re-designed gear set. Trust me, I fliped around my clutch dog and it worked fine for years.

 

[tashasdaddy]

Re: 25hp and 20 hp lower unit

compare parts here. http://shop2.evinrude.com/ext/index.aspx?s1=bf6ad09c53cead335fcfd8a6471c0f7f

 

[redogman67]

Re: 25hp and 20 hp lower unit

I was considering turning the clutch dog around but the forward gear might have damage as well, I looked at that site with the parts but it doesn't really make sense to me. But wouldn't it be easier to just swap the lower units if they are compatible?

 

[jasper60103]

Re: 25hp and 20 hp lower unit

...But wouldn't it be easier to just swap the lower units if they are compatible?

Yes, and it looks like they are compatible IMO. Anyway, it won't cost you nothing to give it a try. If the holes don't line-up it won't work.

edit: pretty sure it should work. The gearcase (#36) part numbers are the same.

Be sure to remove bolt (#54), screws (#5) x 4, and shift rod connector screw (#6).
Also, now is a good time to replace the impeller (#14).
Be sure to lube the driveshaft splines and check o-ring (#11) before putting it back together.
When adding new gearcase lube, replace washers (#45) x 2.

 

[tashasdaddy]

Re: 25hp and 20 hp lower unit

drive shaft are the same also. go for it.

 

[R.Johnson]

Re: 25hp and 20 hp lower unit

The 20 HP gearcase will bolt right on. I have a couple of 57 18 HP engines with with mid 70's 25 HP gearcases.

 

[redogman67]

Re: 25hp and 20 hp lower unit

Hey thanks guys, I called a local mechanic and he said he will have to take a look to be sure they are compatible but if they are he said it would prob be like $60 bucks to change it over, so that seems reasonable over me trying to do it without any experience. so I will just let him do it for that price and I will prob tell him to change the impeller and any cheap gaskets, seals, or o-rings that need it. Is there anything other things you guys recommend me getting replaced while its in the shop that isn't expensive? I was also thinking of asking him to tune and clean the carb but I am not sure if that would cost a lot.

 

[jasper60103]

Re: 25hp and 20 hp lower unit

You could have him pressure test the lower unit before bolting it on. Plus, that would find any leaks.

I personally wouldn't worry about the carb unless it was running bad.

 

[wbeaton]

Re: 25hp and 20 hp lower unit

The 18-20-25 hp all share the same lower unit so its ok to use. Definately have him do the impeller while you are at it. A pressure/vacuum test of the lower unit would be nice, but not critical. Change the lower unit oil too. Unless the motor isn't running properly don't worry about the carb.

 

[redogman67]

Re: 25hp and 20 hp lower unit

Ok I will prob forget the carbs cuz it runs fairly well. Thanks guys

 

[tashasdaddy]

Re: 25hp and 20 hp lower unit

if i was running well, just run it. if you know the difference between a screw driver, and a pair of pliers, and are 1/2 way mechanical, you can do the carbs and anything else on that motor yourself. you just need a OEM service manual, and this forum. the TOP SECRET file at the top of this forum, has great info in it.