80's Evinrude 25HP Questions

[Robert Howard]

I just picked up an 88 evinrude 25hp engine for 50 bucks. It runs excellent, and pumps water to the max, i got a great deal on it. Here is my question i have a 13' valco vee hull 15" transom but the motor shaft is a 20" is this really gonna effect the performance of the boat. It had a 15 on it before, i think it is still gonna get with the program. I also need to know how to change the lower end gear oil. Any help would be greatly appreciated.<br /><br />Thank You<br /><br />Mike.

 

[DJ]

Re: 80's Evinrude 25HP Questions

cropduster,<br /><br />Yes, the 20" on a 15" transom will NOT perform right. It will present a great deal of drag.<br /><br />To change the L/U fluid:<br /><br />1. Remove the upper and lower fill/drain plugs. Drain thoroughly.<br /><br />2. Replace the seals on the plugs-they're cheap.<br /><br />3. Fill the lower unit from the bottom by squeezing oil from the tubes, or better yet, get an OMC kit that comes with a nifty little pump.<br /><br />4. Before removing the tube from the lower fill hole, insert and tighten the top plug.<br /><br />5. Replace the lower plug.

 

[Robert Howard]

Re: 80's Evinrude 25HP Questions

I hear that it is very tough to find a lower end for those engines, because OMC went out of business, how could i go about finding a different lower end?

 

[NathanY]

Re: 80's Evinrude 25HP Questions

I believe that those engines did not use a spacer to make them a long shaft like the older ones did. There for what you would basically be doing is taking that powerhead and putting it on another midsection. Also your lower unit has a one piece shaft, so you would have to get another one to be able to reuse your lower unit. It would be much easier to build up your transom to accomadate the longer engine. Other wise it would cost you more to convert the motor than what it is worth to just buy a short shaft of the same year.

 

[G DANE]

Re: 80's Evinrude 25HP Questions

CropdusterPilot <br /><br />Try to look at your boat and see if it would look silly with 20" shaft ? It can be done by bolting an 1 1/2" plywood plate to the transom, in a size that goes 2" to each side of motor and down to the buttom of transom on the outside. Exceeding hight of cut in transom with 5".Seal with silicone. You can also make it cover the whole cutout on transom. Be sure to get a good quality of marine plywood, paint it before bolting on in boats colour, cut side edges in 45 deg angle. 20" shaft has many advantages if it fits your boat type. Bolt through old motor bolt holes and secure with stainless screws.

 

[Dhadley]

Re: 80's Evinrude 25HP Questions

Or there are companies like Bobs Machine that make small jack plates that will work without messing with the motor.<br /><br />Good luck!

 

[bonitoman]

Re: 80's Evinrude 25HP Questions

DHadley is correct. Get a manual jack plate that will raise it 5 inches or go to a sheet metal shop and have them make one for you that raises the engine 5 inches. You can spend 200 on a maual jack plate or 100 on a plate that is 5 inches taller than the transom. With the manual jack plate you will save on fuel in the long run.

 

[Robert Howard]

Re: 80's Evinrude 25HP Questions

Thanks guys, i think the extension for the transom is the best idea, i had an idea to put a piece of 1 inch thick plywood under a piece of bent aluminum sit on top of the transom and bolt it trough the holes that the transom bolts are through.<br />Really what kind of speed loss am i looking at leaving the long shaft on the motor?<br /><br />think this will work? any feedback will be great.<br /><br />Mike

 

[Robert Howard]

Re: 80's Evinrude 25HP Questions

Oh sh** i forgot to tell you all that there is a five inch spacer piece between the lower end and the midsection.

 

[NathanY]

Re: 80's Evinrude 25HP Questions

If there is a spacer then you could take that out and replace the shaft and shifter linkage and have a shortshaft engine.

 

[G DANE]

Re: 80's Evinrude 25HP Questions

CropdusterPilot<br /><br />I think your speed loss will be around 5 MPH. Are you sure of vintage ? I never seen spacer on eighties 25 HP´s

 

[Robert Howard]

Re: 80's Evinrude 25HP Questions

It looks like a spacer i really dont know, but i tried it on my boat today, it is fantastic long or short it dont matter. It just splashes a lot of water on the transom, but none comes into the boat. So i wont change it over it GPS'S at about 30 with me and a friend in it. To be exact is is 31.3 at WOT<br /><br />Thanks for all the help guys<br /><br />MIKE