25 big twin evenrude

[huntertn]

Ok, I bought this after being told it was a 20 hp..but with a little elbow work,it turned out to be a 25 hp serial nunber 25012 model 70702. Now ,its been about 2 years ago that this was run[or so I was told]but the sparkplug sure looks clean to me.<br /> Anyway,I cleaned it off good inside and out, then sprayed some seafoam in the two heads, and the carb, but with the sparkplugs in, its really really hard to pull. Without the plugs its easy!<br /><br />Now , I have not tried to start it as I just managed to get the 2 line tank pressure tank. I have to say it looks to me as if it was cleaned out befor storing..it has the glass bowl next to the carb and its super clean.<br /><br /> I know I need a new impeller for the water pump after two years sitting, but what is the mix...50/1??? and anything else you guys can suggest???? I havn't gotten a manuel yet, but I ordered one off ebay..just taking its sweet time getting here.....huntertn[james]

 

[Paul Moir]

Re: 25 big twin evenrude

That engine is 35.7 cubic inches, so it's a bit of a beast to pull over. It really needs to be mounted on the boat so you can get your back into it, but you really don't have to spin it too fast for it to start.<br />A few years later with the 40.5CID engines, they put in a compression relief to make it easier to pull.<br /><br />Mix is officially 24:1. Some folks use 50:1 and say it works, but if it were mine I wouldn't. It's got some parts that really need the extra oil. Use TC-W3 rated outboard oil and 87 octane gas. Lower unit oil should be replaced probably. Use 90 weight outboard gearcase lube such as OMC/BRP "HiVis".<br /><br />It's easy to replace the impeller on that engine. Nothing to it. A few seconds after the engine starts, a lot of water should come out the large hole on the back of the midsection of the outboard. Some exhaust leaves through that hole too.<br /><br />"Muffs" don't fit so don't even try them. If you want to start it up on land, do it in a bucket filled over the bolted together seam between the midsection and the lower unit. The water needs to be up that high so the water pump will prime.<br /><br />Good move on the Seafoam. Those old Big Twins are often really crudded up with carbon.<br /><br />Hope some of that helps!

 

[huntertn]

Re: 25 big twin evenrude

thanks...That will sure help! I took the recoil off and used the creep..that really helped,but your right as rain..thats a stiff beast to pull. <br /> Can you tell me if the gas connection on these old ones had a gasket on the fuel line conection at the motor????I connected the gas tank, but its not a tight fit..looks to me that maybe there is room for a gasket in there???? still no manuel in the mail yet

 

[Paul Moir]

Re: 25 big twin evenrude

The fuel line connector should have o-rings to seal it to the connector on the outboard. They wear out pretty regularly and frequenly need replacing or they leak. They're metric o-rings so you they're a little different size from what you'd find at the hardware store.<br /><br />Have a look at this post for tips on how to replace them:<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=28;t=024654 <br /><br />The dealer part number for it is 301824, or aftermarket part number 18-7111. If you know where to find metric o-rings, there 5mm ID x 3mm wide.