L/U interchangeability from '78-115HP to '74-135HP

[ScottieinNC]

Hi all LU gurus.<br />Looking at a parts motor, a 1978 115 evinrude, model # 115899C which has two burnt pistons...anyway, I am mainly interested in the L/U for my 1974 Evinrude 135 model #135489<br />I've found a lot of references here of up to a 1977-115HP L/U working with what I have, just unsure of the 1978-115Hp being compatible.<br /><br />Would any of the other 115 powerhead parts be compatible with my 1974???<br /><br />I can get a good buy on this if it's compatible.<br /><br />Looking forward to your replies, seen some earlier posts and Ezeke and DHadley are a wealth of info.<br /><br />Thanks again y'all!<br />Scott

 

[seahorse5]

Re: L/U interchangeability from '78-115HP to '74-135HP

The 1978 gearcase will not work on your '74 engine. It was redesigned that year to be fully mechanically shifted and similar to the ones used today. Your '74 has hydrallically assisted shifting internalls, and the likage is completely different also.

 

[seahorse5]

Re: L/U interchangeability from '78-115HP to '74-135HP

I forgot to add, the 1978 models used a completely different ignition system, too.

 

[ScottieinNC]

Re: L/U interchangeability from '78-115HP to '74-135HP

I was suspecting of that seahorse...Next question - what years and HP models would interchange?

 

[ledgefinder]

Re: L/U interchangeability from '78-115HP to '74-135HP

1973-77 V4 lower units will fit yours, with the exception I think of the 1977 135hp.

 

[Dhadley]

Re: L/U interchangeability from '78-115HP to '74-135HP

Any 20" V4 gearcase will interchange from 73 to 76. The 77 85 and 115 20" models will have the same bolt pattern and will work. The 77 140 has the larger case and wider bolt pattern as do the 25" 85's and 115's.<br /><br />The linkage can be interchanged but the bolt spacing on the lower unit case is the determining factor.<br /><br />The 78 block has a different mounting bolt pattern but can be retro fitted to go on your 74. You cannot put the 74 block on the 78 mid section without water leaks.<br /><br />The 78 ignition can be put on your 74.<br /><br />The carbs and intake can be used. <br /><br />The crank is the same -- as long as youre sure its a 78 and not a 79.<br /><br />The rods and pistons are the same.<br /><br />The heads can be interchanged.

 

[seahorse5]

Re: L/U interchangeability from '78-115HP to '74-135HP

One thing Mr Hadley left out, 1973 crank and rods had different bearing sizes than the '74 and later engines.

 

[ScottieinNC]

Re: L/U interchangeability from '78-115HP to '74-135HP

Thanks everyone, very, very good advice on this board. If I had bought the 1978-115HP, It looks like I would have wasted my time with the L/U.<br /><br />I'll be looking for year ranges you have reccommended for a parts/LU motor.<br /><br />Thanks again!