25 hp lowerunit

[silver lab]

i have a 78 25 hp 25853c i need a lower unit but don t know .what sizes/yrs will interchange with my motor .help:: the is a long shaft if it matters

 

[tashasdaddy]

Re: 25 hp lowerunit

compare part #s here. http://shop2.evinrude.com/ext/index.aspx?s1=86d3d72aeba35dacbc349b439cb45104

 

[restornator]

Re: 25 hp lowerunit

as long as the drive shaft is good, you can get any lower unit from as early as 1956. You have a special year, everything earlier had a shear pin prop shaft (you will need a new propeller as well), everything later has a different pinion gear (which i do not know how many splines or if it is compatible). If you can find out more info on the pinion gear, you may be able to use a 25hp lower unit up to 1984

This is just my educated guess and i may be completely wrong too

 

[TN-25]

Re: 25 hp lowerunit

A 1978 25 horse was the next generation of 25. That motor shared nothing with the 18-20-25 horse motors up to 1976 except perhaps spark plugs and gas tanks; the 1977-on were different and were based on the 35 horse that was introduced in 1976. Yours would not have come with the through-prop-hub exhaust but eventually they got that feature. I would think that the lower unit from a 1977 through the new millenium would fit, but as I said the through-prop-hub exhaust was added somewhere in the mid 1980s.

 

[restornator]

Re: 25 hp lowerunit

A 1978 25 horse was the next generation of 25. That motor shared nothing with the 18-20-25 horse motors up to 1976 except perhaps spark plugs and gas tanks; the 1977-on were different and were based on the 35 horse that was introduced in 1976. Yours would not have come with the through-prop-hub exhaust but eventually they got that feature. I would think that the lower unit from a 1977 through the new millenium would fit, but as I said the through-prop-hub exhaust was added somewhere in the mid 1980s.

the mounting pattern and pinion gear was the same at least back to '68, if you look at the gearcase extension, it's the same part number. this is also true for the water pump assy. At least a later lower would mount correctly, and a newer thru-hub gearcase would not work because he would then need the correct exhaust housing. They also changed the pinion gear in '79, which may mean there is a different number of splines. The drive shaft diameters were the same.

 

[restornator]

Re: 25 hp lowerunit

i can comfirm that 1978 is a unique year. anything 1979+ will not work because the driveshaft is a larger diameter starting in 1979. Lower units prior to 1978 will work but you will also need to find a shear pin compatible propeller.

How do i know? I have a gearcase housing for 1979-84 and a driveshaft from a 1970 25 hp will not work but is the equivalent part from a 1977 driveshaft. The driveshaft on 1978 models is 1/2 pound lighter than previous years, which i think is the only difference.
If you still have the driveshaft and plan to re-use it, you can get a lower unit from any previous year 18/25 hp. 1968 and newer have the modern look.

 

[silver lab]

Re: 25 hp lowerunit

thanks for all the advise ,i am new to this forum .you all have been great help i am gona try to rebuild mine ,gona rip it down this weekend thanks agin

 

[silver lab]

Re: 25 hp lowerunit

.i found that my lower unit will kick out of gear with a load on ,so i took the control cables off and it still dose the same thing in forward.any ideas on what it could be .i was told that is clucth i the lower unit .is that right .is it hard to change.

 

[Happyfingers]

Re: 25 hp lowerunit

i have one but im in Australia which prolly isnt gonna help

 

[silver lab]

Re: 25 hp lowerunit

no that won"t help shipping along would kill me .but thanks

 

[silver lab]

Re: 25 hp lowerunit

i found that i need a clutch dog 031650 and aforward gear 0389236 but the price form my local dealer 425 for both thats crazy .any body have any other opptions .i have looked on ebay but can't find any .help