Merc 500 Revival

[merc850]

Re: Merc 500 Revival

You should have the fuel system working when you test the compression, for oiling reasons, so I would install the end cap then spin it over to test. You can test it later when it's warmed up for an absolute reading.
Follow these steps to reinstall cap: The seals should have Loctite on their metal frames when installed and grease on their lips, put Perfect Seal or Permatex on the Oring area and some oil to help slide the bearing cap into place.
Push the cap back in (make sure that the bolt holes are lined up) and you can lightly tap it in for final seating.
Replace the cap bolts and tighten the crankcase bolts. Make sure to reinstall any shims that have been installed.

 

[spamn]

Re: Merc 500 Revival

Thanks for all the help. Got the lower unit complete today. Service center is pressing in new oil seals tomorrow. Hope to have it all back together this weekend. What type of sealant do I need to use on the gaskets? Powerhead to exhaust plate, exhaust plate to drive shaft housing, etc.

 

[ajgraz]

Re: Merc 500 Revival

Maybe I missed it, but did you clear up the mystery of the non-fitting impeller? Does the old impeller have a part number on it, can you confirm it's the same? Could there maybe have been some mid-year production change on the water pump design?

 

[spamn]

Re: Merc 500 Revival

Sorry, I left that out. Still an unsolved mystery. I ordered a new one (same part number) and it came in today. Fit like a glove. No idea why the other didn't.

 

[ajgraz]

Re: Merc 500 Revival

Sorry, I left that out. Still an unsolved mystery. I ordered a new one (same part number) and it came in today. Fit like a glove. No idea why the other didn't.

I have an idea, and it begins with the letter "China."

Sounds like you're going to get this motor purring soon enough.

 

[spamn]

Re: Merc 500 Revival

For those that care, I got the seals pressed in today and the bearings greased up. Had to drive hours to find a shop that had a powerhead gasket in stock (who'da thought people don't readily stock parts for a '78 Merc). Finally got the gasket and hoping to get the ratchet turning tonight. Also picked up some Quicksilver gear lube and some OMC sealant for the gaskets. Not sure if that's necessary, but I scraped old sealant away when I took everything apart so I figured I would use sealant as well.

Hope to get the powerhead and lower unit all on tonight. If I'm lucky I can get a compression test done as well. Can I just turn the flywheel for that or do I really need to crank the engine? It'll be too late and I don't want to wake the neighbors. May have to do that in the morning.

Only last thing that I noticed is that when I took the powerhead off and layed it on the garage, I broke the choke solenoid plunger off on accident. Noone has that in stock but I can just use the manual choke and be fine, correct? I'll order the plunger later.

While waiting for parts and what not the past few days, I rewired all lights, installed a Garmin 400c into the bow, sealed up holes in the transom from that last engine, and tinkered with about a 1000 other things. It was 78 degrees today and I've got the boating fever.

Well, wish me luck. Hoping that with a few Budwieser and a few hours, she'll be ready to crank.

 

[ajgraz]

Re: Merc 500 Revival

Yeah, you really gotta go at cranking speed to get a compression reading. It'll take 5 or 6 rotational cycles before the gage levels off anyway. Don't forget to hold the throttle plates (butterflies) open.

 

[ONERCBOATER]

Re: Merc 500 Revival

save the parts of your choke solenoid if it broke where i suspect it did I have a fix for it.... for my 78 merc 200 (20hp) the solenoid plunger is NLA so i had to get creative and fix mine....

Sean

 

[glastronomic]

Re: Merc 500 Revival

Spamm, excelent topic.

 

[spamn]

Re: Merc 500 Revival

Welll, I got the boat in the water yesterday just to get a good feel for the engine. Here are a few problems I noticed

Telltale starts off as a stream but becomes a drip
Engine only starts on full choke, even after running for a while
Engine dies when put into gear
After several minutes of running with idle lever full forward, engine will go into gear but has little to no power.

I checked the compression, but readings didn't make sense so I will do again today. Can't get compression tester on to fourth cylinder as lower cowl blocks installation. Carbs were never cleaned and I'm thinking/hoping that cleaning them will solve 99% of problems, but that's being very optimistic.

Going to remove lower unit again and check prop condition after running since little to no water was coming from telltale at times.

Engine didn't sound too bad, maybe a bit lower RPMs than it should. Smoke was nice color and not too much.

Lastly, realized that broken electric choke sucks on this engine, as you have to remove the upper cowl to pull manual choke.

 

[glastronomic]

Re: Merc 500 Revival

Welll, I got the boat in the water yesterday just to get a good feel for the engine. Here are a few problems I noticed

Telltale starts off as a stream but becomes a drip
Engine only starts on full choke, even after running for a while
Engine dies when put into gear
After several minutes of running with idle lever full forward, engine will go into gear but has little to no power.

I checked the compression, but readings didn't make sense so I will do again today. Can't get compression tester on to fourth cylinder as lower cowl blocks installation. Carbs were never cleaned and I'm thinking/hoping that cleaning them will solve 99% of problems, but that's being very optimistic.

Going to remove lower unit again and check prop condition after running since little to no water was coming from telltale at times.

Engine didn't sound too bad, maybe a bit lower RPMs than it should. Smoke was nice color and not too much.

Lastly, realized that broken electric choke sucks on this engine, as you have to remove the upper cowl to pull manual choke.

Pilot jet/mainjet blocked (Choke start/run only) clean out carby)

 

[ajgraz]

Re: Merc 500 Revival

Pee stream: make sure the water tube-into-pump body has the rubber seal (looks like a bit of hose) and rubber cup washer on it. Those parts deteriorate or get lost, and people forget to replace them. Without them not all the pumped water gets up the tube.

Running issues: as said above, a good carb cleaning will do you wonders.

Compression: what numbers did you get? Also, there are compression testers that have a fitting that screws into the spark plug hole, then hose, then the gauge...may want to look into one of those.

Broken choke plunger: metal cylinder with a plastic, hooked "arm" sticking out the bottom? Did the plastic break in the middle? You may be able to use some bailing wire to replicate the broken off bit of the plastic arm, at least as a temp fix...I've done that before.

 

[spamn]

Re: Merc 500 Revival

Yeah, the lower unit needs to come off here soon so I can double check my rebuild of the pump and everything. Hopefully I didn't fry a brand new impeller already. I put in the new seal and washer, but may have done something wrong there.

I purchased some spray in carb cleaner but have now been reading that you shouldn't use that? Any optinions on that? I know the best thing is the take the carbs apart and clean them, possiblby replacing floats and what not, but I'd like to try a simpler step first to see if I can get any improvement. Maybe a nice DIY carb cleaning and reassembly thread? I looked and the rebuild kit (which I don't know how much of it is necessary) is $70 and I have two carbs. $140 for a kit plus my own labor of cleaning.. I'm pretty sure I've heard of shops doing a carb job a lot cheaper. Anyway, please inform on what to check out on the carbs and if I can use the spray cleaner. I have spare plugs on stand by because I know those cleaners foul them out quick.

Compression.. they were all within 10 psi of each other. I couldn't get to that bottom cylinder though. The kit I have does have the fitting, but that doesn't make it any easier. Ther is like a 2.5" gap between the bottom cowl and the plug hole. I can barely get a plug in there. EDIT:
Just read my Seloc manual and read that I did the test incorrectly. I only removed one plug at a time. Also, it says to ground plug wires.. how do you guys do this? I simply out electrical tape over the wire to stop the spark. Probably not the best idea.

Yes, that's the plunger I'm speaking of. The plastic arm broke off right at the base of the plunger. I could rig something up, I'm sure but I can just use the manual choke for now and when I order new parts, I'll just throw a plunger in as well. No rush on that part.



Other news.. I realized that being new to boats isn't fun. The controls I had were on a Merc 402 and I never adjusted them.. I have no idea how I over looked this. I played with the cables today and noticed at full throttle (according to the lever), I was actually at like half throttle, at best. I adjusted the cable in to help with that. Shift cable seems alright, but again, I have no idea.

 

[spamn]

Re: Merc 500 Revival

Just noticed some replies. Thanks for the input guys. Barring good compression, I whole to be pulling in the bass next month.

 

[spamn]

Re: Merc 500 Revival

Last thing for tonight is I noticed an electronic of some sort with two wires coming from it. One wire is completely broken off at the base. From all my research this is the "mercury switch" also called "safety switch". The engine still cranks so I'm assuming the engine won't be killed when the switch is supposed to do so. Is this the correct idea is what that is?

 

[ajgraz]

Re: Merc 500 Revival

Wire off the bottom of the safety/mercury switch is the ground wire, yes those do break off and in that case the switch won't do diddly.

For the carbs, you don't need the $70 "repair kit" unless there's some broken parts in the carb; you just need the $2 "gasket kit" in order to disassemble, inspect, clean, and (if nothing's broken) reassemble. And you are right, just spraying them from the outside will do almost nothing, you gotta dissasemble and soak the parts in solvent in order to de-gum all the passages.

EDIT: it isn't fun now, but as you learn, get better, and overcome difficulties, then it becomes more fun than you can imagine.

 

[spamn]

Re: Merc 500 Revival

For my engine, there is several gasket kits. Any idea on which I may need?
http://www.boats.net/parts/search/M...0 THRU 5531629/CARBURETOR ASSEMBLY/parts.html

It is still fun. Sometimes frustrating, but I think that working on your boat is half the fun of owning one. I redid the compression test last night and still cannot get to that bottom cylinder. I will try again tonight. I did the test initially with only one plug out and got roughl y30 PSI per cylinder. That was scary. I cannot find the exact specs on what it should be, but I don't have more than a 10 PSI difference between so that is the important thing. Hoping to use an additive to possibly clean some carbon off the cylinders and gain a few PSI back.

Lastly, can anyone tell me what tachometer it is that will plug into my Mercontrol? I'd like to add one on to see exactly what the engine is doing. Also, how accurate is it since it's through the controller?

Parts list to get:
Choke Plunger
(2) Carb Gasket kits
Safety Switch
Tach w/ harness
Case of Budweiser

 

[spamn]

Re: Merc 500 Revival



Now what?

Just finished compression on all FOUR cylinders (finally got the lower) and all read 100 except one is 95.
I don't want to take anything off of the carbs before I know exactly what I'm doing.

Also, I removed the lower unit once again to check it and the impeller is still perfect. I double checked the washer and sleeve inside the water pump housing to the water tube. That's good. Guess I need to find and check the t-stat as well. EDIT: I thought I was crazy, but some reading confirmed that I am not. This engine does not have a t-stat or poppet valve.

The ground on the safety/Mercury switch is the only wire attached. I do not even see any other wires in the engine that are loose or could be attached to the safety swtich.

Lastly, there is a black plastic piece that goes in the bottom of the drive shaft housing. It has two holes. One for the shift rod. It has one flat side. Which side faces the lower unit? I found that this was broken. Thinking I put it in wrong and that may explain my problem shifting into gear. Thankfully, I have a spare from my other engine but don't want to put this one in wrong as well. Sorry if the explanation is bad, but I cannot find the name of the piece on any diagram.

 

[ajgraz]

Re: Merc 500 Revival

Reverse lock rod guide, maybe? The shift shaft would go through the big hole, the lock rod through the smaller. I'd think the flat side faces down toward the LU.

Seloc guide is good enough for a carb disassemble, just be sure to positively ID the carb type first (book usually covers many year/hp ranges).

Compression sounds good to me. You'll never get an actual psi "spec" on compression because it depends on so many variables (temperature, cylinders clean or dirty, etc.)

 

[spamn]

Re: Merc 500 Revival

Got the carb apart LATE last night and cleaned. Upper carb looked pretty perfect but cleaned it anyway. Lower carb (gravity did it's job) was horrible. The high speed jet was pretty clogged up, the idle tube was black and crusted shut, and the main nozzle running up from the bowl was completely blocked off with hard black carbon.

Filled an ammo can with B-12 and let the small pieces soak. I sprayed down the main pieces and scrubbed with a small metal brush. I had no idea what I was doing really, but it looked mostly self explanatory. Now to get all the screws adjusted properly. I'm going to try what Seloc says and hopefully can fine tune from there while it's running. Hoping to try it out in water again this weekend.