1957 Johnson 7.5 impeller /powerhead gasket

It's an AD-11, 1957 Johnson 7.5 hp.<br /><br />I have to change the impeller. In reading the archives, I learned that the only way to disconnect the shift linkage was to remove the powerhead. I also learned that a gasket will have to be replaced when the powerhead is reinstalled, and many folks seemed to be making their own. I can deal with tracing out the old one onto gasket material and cutting it out, but what is the correct gasket material for this? I have on hand some light green paper gasket material that I have used for exhaust gaskets on some mopeds. Will this suffice?<br /><br />Is it *absolutely* necessary to remove the powerhead to get to the shift linkage? I'm sure it's not *that* big of a deal, but if there's a shortcut someone could turn me on to it would be much appreciated. The impeller change on my 1980 Johnson 4.5 was a cakewalk, as was the one on an Evinrude 70hp I owned for about 8 years.<br /><br />One last thing... what the general concensus regarding the reliability and overall "fav" rating of this motor? It's always run well. I started it again last night for the first time in about 9 years, and it only took about 10 pulls... with no priming. Just hooked up the tank, a couple pumps on the button, choke, etc. Once it was running, it fired first pull just as it used to years ago. I love the thing....<br /><br />Thanks guys-<br />Brian

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Hi Brian,<br /> If the material you've got is a fiber gasket material, then you'll be fine. <br /> You MUST remove the powerhead to do this job - no way around without breaking stuff. It's not hard - pull the fuel and air hoses off the powerhead, remove the seven (maybe eight?) screws off the base of the powerhead and off it comes. Take care to return the washers, spring, and carbon seal in the correct order upon reassembly. Grease the splines, too.<br /> The '54 to '58 Johnrude 7.5s were great little motors. Lightweight, decent power and reliable as all getout. I have a '55 and that is soon to move into it's third generation of service in our family.<br />- Scott

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Thanks for the response. I'm not sure if the material I have is "fiber" or not... I bought it at a parts store, and it's about the thickness of the cardboard tube found in the middle of a roll of paper towels. Feels like it's made of paper/light cardboard. Does that sound like the right stuff?<br /><br />I'm a little scared off by your mention of springs and a carbon seal, but I'm sure that like always, I'll find it wasn't that big a deal after all.<br /><br />Funny you mention "light weight". Seems to me that old motor weighs just about the same as my 1980 Johnson 4.5hp, although I don't have figures to back that up. They weigh very close to the same though, I'd guess. Surprising...<br /><br />Thanks for the help-<br />Brian

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Ah, they were still made of aluminium back then too. Nowadays they have heavy plastic peices to replace the Al ones.. <br />You've got the right gasket material - you just want to avoid rubber and rubber like gasket material. Or cork. None of that will stand up long.<br />A common hole-punch is really helpful, and if you can get the old gasket off in close to one peice, it'll be very helpful as a template.<br />Don't worry too much about the springs and such. If they all go flying (which they won't) we'll be here to set you straight. <br /><br />Good luck!

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Here is how I did it on my 5.5 which is pretty much the same thing.<br /><br /> http://www.outboard-boat-motor-repa...ower Unit and Replace Impeller Water Pump.htm

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Thanks to you all. What a great help, and very reassuring. I'm hopefully going to tackle it this weekend.<br /><br />Brian

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Why not buy the proper gasket, it is still available

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Why not? Because I'm impatient by design. A fault of mine, but I deal with it and it almost always works out. I can make a gasket. I might not be able to get one shipped to me by this weekend, and really want to get the motor running. If a homemade gasket will work as well as a factory one, I'd rather make it myself and save the money, shipping time, etc. That, and the warm fuzzy feeling of being able to say I made it myself.<br /><br />I don't view that as a problem. YMMV.<br /><br />Brian

Re: 1957 Johnson 7.5 impeller /powerhead gasket

Hey G26, Chinewalker definitely knows what he is talking about. The job is not bad, but watch out for a couple things. One piece on the shaft is black. It is made of sintered metal (Powdered metal that is compressed and fused together by electric current. This piece is very brittle (Yeah I broke mine the first time.)<br /><br />You have to remove the power head. The gaskets are fiber. Around here, I can no longer order any parts for OMC. From my understanding, Bombadier will no longer stock andy parts older than 12 years. I bought the last two gaskets from a dealer who still had some stock.<br /><br />The motors are tanks and will work well for many years. Definitely watch the order of the pieces on top of the shaft. Good luck.