preventive maint. on old but newly rebuilt motor

[greasemonkeyozi]

I have just posted one fault on a topic about a water leak on this motor, and figured I needed to create a new one since this is a different topic. <br /> I had bought this old 75 70hp 3 cyl and finally got her working right. So far, I have (1) replaced all frayed wiring and connectors and lubed all points to prevent corrosion. (2) replaced switch box and reset timing. (3) replaced spark plugs and repaired some exposed plug wires. (4) rebuild, reset, and tuned carborators. (5) replaced all hoses both fuel and water. (6) replaced fuel pump diaphram (7) Replaced prop with smaller one to prevent me from sheering it again. still get same performance though.(8) changed out lower unit gear oil and notice white milky color. Dont know how long it has been since last changed though.(8) ran compression test, all checks good at 150psi.<br /> Now that I have finally got her to run like new,"Knock on wood," have I missed anything as far as preventive maint. Any advise will be appreciated.

 

[roscoe]

Re: preventive maint. on old but newly rebuilt motor

Keep an eye on that lower unit oil. Check it after using it once or twice. If milky again, you have a leak and water is entering the unit. Could be a gasket/o-ring on the fill/drain screws. Or it could be prop, drive, or shiftshaft seal gone bad.

 

[BF]

Re: preventive maint. on old but newly rebuilt motor

what about servicing the water pump? Impellers go bad whether they're being used or just sitting. Are you getting good water flow now? Even if you are, I'd be concerned about having a brittle impeller break apart. The danger is that you overheat/cook the motor before you notice the poor water flow. Impellers are normal wear items... some say change them every season, on mine (low hours, freshwater) I'm content to go 2 or 3 seasons (as long as there is no indication of a problem, like a weak "tell-tale" stream). <br /><br />Also, if the motor is new to you, you can't be sure that someone who didn't know better didn't run the engine without a water supply. Even 30 seconds can melt/damage an impeller.<br /><br />I also second the water in the lower unit concern. If there's water in the LU after an hour or two of use, then you've got a problem. Taking LU off and pressure testing it would tell you where the leak is.<br /><br />I'm not sure if your motor has a magnetic drain plug in the LU. If not, maybe an update to a magnetic one is available from a dealer. Watching for filings accumulating on the magnet is a way of getting an idea of the health (or lack of it) of your lower unit/gear set.<br /><br />Good luck!<br /><br />Brent

 

[andrewkafp]

Re: preventive maint. on old but newly rebuilt motor

You just about covered it all BF <br /><br />Make sure those washers are in the fill/drain holes on the L/U (A lttle tip.. the later Merc ones are a light blue colour so you can see them in there when you are checking or refilling.)Replace your black or clear ones with them.

 

[greasemonkeyozi]

Re: preventive maint. on old but newly rebuilt motor

Hey thanx. Im gonna take her back on the lake this weekend and recheck my lower unit fluid afterwards. I may use some thread tape on my fill and drain plugs. <br /> So far, I have done alot of restoring on my motor and I am kind of afraid of the Idea of replacing my impeller, although, the last person who owned it before me claimed that he has replaced the impeller. I dont trust him, its just me and my motor now. Is it a hard task, and what is the man hours Im looking at? I do have a manual so proper guidance isnt gonna be a problem.

 

[greasemonkeyozi]

Re: preventive maint. on old but newly rebuilt motor

By the way, about those seals and impeller. Give me a good referance related to this site to order my parts I need.

 

[ZmOz]

Re: preventive maint. on old but newly rebuilt motor

I would strongly suggest you get some Seafoam "deep creep". My '74 150hp Mercury was getting pretty hard to start and could not get very high RPMs under load. I sprayed a bunch of this in the motor...WOW. I would have NEVER thought anything in a spray can could have such an effect...and it was only $5.99 at napa.

 

[andrewkafp]

Re: preventive maint. on old but newly rebuilt motor

Don't change the impeller if it has been done recently. It the taletale is strong and the water is lukewarm to cool.<br />They recommend changing it every couple of seasons as it may become brittle and start breaking up. <br />If you decide to do it..check out Merc90hpnewbie's posts. He recently did his 1st impeller with success<br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=008376

 

[Just Jed]

Re: preventive maint. on old but newly rebuilt motor

All great advice guys. Just like to add two things to the list.<br /> 1. Get the manual.<br /> 2. Keep visiting this sight.

 

[BF]

Re: preventive maint. on old but newly rebuilt motor

changing the impeller isn't too bad. It sounds to me like you've already done things that would be a bigger pain! It's basically learning how to drop - err I mean take off - the lower unit, and put it back on. The impeller sits in a housing (cap) on top of the lower unit... usually 4 or so bolts holding housing on. I was leary the first time I did it too... now I've done it on 4 different motors... it's amazing to me that the procedure is the same on my 2 hp as it is on my 150 hp! Just the bolts are in different places, and there are fewer of them on the 2hp. If lower unit comes off OK, it's probably a <2 hr job start to finish. For bigger motors like yours, an extra set of hands is handy when your trying to get the LU back on, someone to move the flywheel a bit.<br /><br />If you've got good water flow, and think the impeller has been changed recently, then I agree, it can probably wait. It would make a good project in the off season, if you've got one there. <br /><br />Oh, and sometimes it's nice to take it apart before you get/order the parts. Depending how things look, you might want to do the whole pump rebuild -new housing etc, or just change the impeller. It's possible the water in the LU was leaking in from under the pump, that's why pressure testing is helpful. BTW, if those seals are gone, they're usually not included in the basic "pump kit"... new pump base & seals would be a separate part.<br /><br />Hope this helps,<br /><br />Brent

 

[andrewkafp]

Re: preventive maint. on old but newly rebuilt motor

You can go here<br /><br /> http://www.myfishingpictures.com/showgallery.php?cat=527 <br /><br />Saerch for "Hoo's yur daddy" pix and you will find a series of pics show water pump replacement.<br />It's a Yammy, not a Merc, but the principal is the same.