Old Merc, can it be saved?

[baby_hewey]

I have been given a 15 ft. Tidecraft w/ 40hp Mercury 405 motor, boat and motor are 1977 model. This boat has been left out in the weather for about 5 years, long enough for the canvas cover to rot completely off and for it to fill up with Pine straw. I know that it will need much TLC as much of the wiring's insulation is cracked and rotting. Now I am trying to get it back to running order for use with my son, but every place I look shows the 402, but no reference to a 405, I am wondering what the difference is. This is a long shaft motor with remote throttle and streaming. Any info would be of great help.

 

[Clams Canino]

Re: Old Merc, can it be saved?

How many cylinders is it? (count the spark plugs)<br /><br />-W

 

[WillyBWright]

Re: Old Merc, can it be saved?

Never heard of a 405, just the 402. That's a 40 twin that's rather gutless, but they work. The good 40s are the 4-cylinder models. They have alot more power. I know they're both 40Hp, but believe me there's a huge difference. Lots of both still out there chugging away.

 

[baby_hewey]

Re: Old Merc, can it be saved?

Ok, My fault for not cleaning things before asking questions. This motor is a Mercury 402 40 h.p. made in 1973. This is the 2 cylinder. Is is worth working on? What will need to be done? and Where do I start?

 

[tengals123]

Re: Old Merc, can it be saved?

have you tried turning her over?

 

[baby_hewey]

Re: Old Merc, can it be saved?

No, the battery cables are rotted and will have to be replaced before I can try the starter. Also, I just recevied the gastank Saturday, but I am still missing the fule line. <br /><br />I did pull on the pull start and the motor seemed to move and sound normal. That is as far as I have been able to go so far, I am still collecting parts from the garage of the donor. I think that I should be able to try cranking it Friday or Saturday, if I get the rest of the parts. I am real reluctant to spend any money untill I know what I am looking at, a little better.

 

[Clams Canino]

Re: Old Merc, can it be saved?

OK... 402. Good motor, part of the "direct charge" family of outboards that came in 2,3,4 and 6 cylinder versions. A compression test will tell the tale if the comprssion is good, then a carb-cleaning and waterpump impeller are a "must" for preventive maintanance.<br /><br />-W

 

[tmcalavy]

Re: Old Merc, can it be saved?

Do as Clams and other have suggested. If it checks out, proceed slowly to check the ignition for fire, the wires under the cowl for decay, and the wiring harness for decay. I've done a 73-73 Merc 500 slowly over the past 2 years and now it's a very reliable outboard. The wiring isn't hard to do if you go slowly and use marine wire. Replacing the whole plug-in harness can be a different matter. Luckily mine is in pretty good shape.

 

[Kenny Bush]

Re: Old Merc, can it be saved?

Baby Hewy, clean here up and run her. Double mix the oil for testing, and after warming her up, check the compression. Post back.... That aint no dinosaur... She is glad to be back....

 

[baby_hewey]

Re: Old Merc, can it be saved?

All, right this is the kind of info I was praying for. One major question: How do I test the compression?

 

[baby_hewey]

Re: Old Merc, can it be saved?

Also, Clams, thank you for specifing that this is one of the DIrect Charge motors that you discussed in another thread. I am very happy to have that guide to help me. I know that my first step is to replace the battery cables as the insulation is brittel and large sections are missing. What else should I work on before I try to crank it for the first time? I am real worried about the 'pee hole' as I have seen it discussed, I am concerend that there is trash in the system as there a build up of crap at the opening. Should I drop the lower unit and start with that before I start trying to crank it?<br /><br />This boat and motor are a project for me and my two sons to work on; it gives us time to spend together and I can try to teach them how to work on their own stuff. So I just want to tell every one here thank you for the help, it is really nice to find a site like this on the net.<br /><br />Thank you

 

[tmcalavy]

Re: Old Merc, can it be saved?

You can get a compression gauge for little $$ at a parts store or Harbor Freight. Might want to drop the LU and inspect the pump and rotor, and check the oil/lube level and condition. Compression should be above 95-100 in all the jugs...what matters is no more than 10-15% difference between cylinders. You can squirt a mist of premixed fuel into each jug and turn it a few turns by hand before the compression test and before firing it over...doesn't hurt to keep the innards well lubed.

 

[Clams Canino]

Re: Old Merc, can it be saved?

A compression tester is around $25 at Sears, good investment. Let me add that once it's running, decarb it with Mercury Power Tune and retest. If the compression came up, do it again. Sticky rings are a known issue.<br /><br />-W

 

[Kenny Bush]

Re: Old Merc, can it be saved?

Get a manual first..... also dirt dobbers love that pee hole. blow it out with air or little piece of wire. I have retaped those crumbling wires as long as the wire is not corroded (green). Compression guage is 15-20 at any autoparts store, even sears..... Just screw the guage into the spark plug hole and spin her over about 5 seconds and watch the guage record the maximum compression. record it. do the other cylinder. record it and compare. They should be close together at about 115-120 lbs....post back with readings.

 

[briannh1234]

Re: Old Merc, can it be saved?

Hewey -<br /><br />When I had the l/u off my motor I was able to rig a garden hose to where the water pump connected. I kept the pressure low and got a nice steady stream of water out the pee hole. I started the engine like this.<br /><br />Seems you could do something simular to flush out the water jacket on your motor and make sure it's working properly b4 you start it.<br /><br />Good luck<br />- Brian

 

[baby_hewey]

Re: Old Merc, can it be saved?

Great Info, this site is great. <br /><br />I have several issues with dirt dobbers, and one is the pee hole. I also have several issues with wires being corroded. <br /><br />But my big problem is that I was handed a small oily part that has the remnants of two wires comming out. It is about an inch long and rounded on one side. Any hints as to what this is or where it goes? Just please tell me it is not an expensive part.<br /><br />Compression is 115 on upper and 119 on lower, but I don't think it is all that accurate as I got that from pulling on the string as I am still working on getting the electric starter going.<br /><br />Thanks again

 

[Ben Konopacky]

Re: Old Merc, can it be saved?

B-H the part could be a mercury safety switch,<br /> its purpose is to prevent a start up with the enging out & up. Location is near the sw.box or distributer ,

 

[tengals123]

Re: Old Merc, can it be saved?

sounds good compression. I'd run the donk 1st for a few secs to she if she fires, before dropping the LU. If she fires, cut off straight away and then continue your repairs. Ie fuel pump, plugs, water pump, seals LU oil, etc. cheers

 

[Motor Boater Bill]

Re: Old Merc, can it be saved?

Parts lists with picutres are available online at mercruiser.com, and may help with identifying your mystery part. The wiring diagram for the 1976-1978 402 does show a "Mercury switch" which would connect to an organe wire from the switchbox.<br /><br />Also, FYI, on some motors you can damage the rectifier if you start the motor without a battery connected--I believe this would apply to yours. This can be avioded by disconnecting the wires from the stator to the rectifier and insulating them. Of course for motors where the battery provides the juice for the spark this does not apply, but I believe your 402 can start and run without a battery (pull start) so keep this in mind when you get ready to test it. If you do blow it or if it is already blown, it can be replaced with a cheap one from Radio Shack, according to others who have done this.

 

[Motor Boater Bill]

Re: Old Merc, can it be saved?

Oops, that should read "orange wire" not "organe wire", above. And the wire comes from the terminal block, not the switch box, but at the terminal block it connects with the orange wire from the switchbox and the orange wire in the internal harness. Others can confirm this, but I believe you can leave this part off without problems, just don't start you motor in the up position--that is what it does, kills the motor if you tilt it up when running or try to start it when out of the water.