drsmooth
drsmooth HalfDork
10/24/20 12:48 a.m.

To be more specific, Learn me the 1987 version according to the serial number (short shaft).

Just bought one, it runs great, fires up on the first pull, but I know little about the motors. 

What things should I get done to it right away for piece of mind, what are the common failure items, what spares should i keep on hand, and what other advice does the GRM collective have on this motor.

Specific question, what is the correct fuel\oil mix ratio?

stuart in mn
stuart in mn MegaDork
10/24/20 6:18 a.m.

A couple owner & operation manuals are here: https://www.manualslib.com/products/Mercury-9-8-Twostroke-3984941.html

 

11GTCS
11GTCS Reader
10/24/20 8:26 a.m.

50:1 on the fuel / oil ratio.  Use a good quality 2 stroke oil for outboard motors if possible.  (TCW3 I believe)  Make the gas tank is clean inside and best to not let fuel sit too long, I like to add marine Stabil as well.  A new water pump impeller is likely needed and change the gear oil in the lower unit.  Both of these are easy jobs with standard hand tools.  

TJL (Forum Supporter)
TJL (Forum Supporter) HalfDork
10/24/20 9:01 a.m.

Does it have a "tell tale" to show water flow? A water pump and lower unit lube service is pretty standard. 

mtn (Forum Supporter)
mtn (Forum Supporter) MegaDork
10/24/20 9:47 a.m.

I’ll second everything everyone has said, and also add that you if it is going to sit for a long time (2+months, especially in cold) you should fog the cylinders, after disconnecting the fuel line and running the engine out of fuel, put stabil in the tank, and fill it to the tippity top to avoid confederation.

 

That was autocorrect, I meant condensation but you don’t want these old motors to confederate against you either. So I think the advice still stands. 

drsmooth
drsmooth HalfDork
10/24/20 6:21 p.m.

Thanks for all the replies.

Looks like I have a few jobs to do over winter!

drsmooth
drsmooth HalfDork
10/24/20 10:21 p.m.

Follow up questions.

 

1. Is the cooling system self draining? Just to be safe i am going to blast some air thru it because it is going to get close to freezing tonight. 

2. Does anyone know the temprature the thermostat opens at? Somewhere i read 140f but i want to make sure. 

3. Does anyone know how best measure temprature on an outboard? I have a laser temprature measuring device i was hoping to use, where should I aim it at? Or is there a better method?

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/24/20 10:45 p.m.

Subscribing because I want to reply when I'm not challenge-drunk exhausted.  I'll see this in "my posts" tomorrow and wonder why it's there and probably reply.

 

mtn (Forum Supporter)
mtn (Forum Supporter) MegaDork
10/24/20 10:45 p.m.

Store the engine trimmed down, it should drain. 

Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) UberDork
10/24/20 10:53 p.m.

If it's accessible where you are, I would use only ethanol free gas. Don't omit the Stabil, though. Use it always.

 

mtn (Forum Supporter)
mtn (Forum Supporter) MegaDork
10/25/20 12:16 a.m.
Floating Doc (Forum Supporter) said:

If it's accessible where you are, I would use only ethanol free gas. Don't omit the Stabil, though. Use it always.

 

Yes - you'll get far better fuel economy, it will just run better, and less condensation.

drainoil
drainoil Dork
10/25/20 10:30 a.m.

Sounds like you have yourself a good well running motor. I agree with running non oxy fuel. I only fog an outboard if it's going away for winter storage, but it won't hurt anything if it's a lesser time frame.  Being it's a smaller motor and easier to move around, and if you live in a cold winter climate, I'd highly recommend bringing the motor and putting it in the house so it's in climate control.  If it's in say, the basement, it likely won't be susceptible to mice and/or squirrels feasting on the wiring. 
 

edit* Regarding proper operating temp I've wondered what it should be on mine (older Merc 50 horse). A few old timers that have really helped me out a lot on this thing have all said that so long as the water stream coming out of the motor, is warm, and there are no running issues, call it good. 
 

I also would like to have a tachometer for my old motor but these old outboards you have to let your ears be the tach lol.

 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/26/20 9:29 a.m.

They are remarkably simple and bulletproof things.  Carburetor, CDI with a couple mags on the flywheel, two spark plugs.

IIRC, the 80s versions should have a whizzer to indicate water flow.  It should "pee" from the back of the cowl.  If your model has a thermostat, it will only pee when the stat is open, so don't panic if it isn't whizzing from that tube.  Run it for a while.  If it doesn't start peeing, so a quick check on head temps (carefully so you don't get burned).  The head should be almost too hot to touch, or you should be able to keep your fingers on it for a couple seconds depending on your heat tolerance.  If you burn off your fingerprints and it's still not peeing, then you have either a water pump that isn't pumping, or a thermostat that isn't opening.

Follow the pee tube back to the block.  If it meets up with a miniature thermostat housing, you have a stat.  If it just attaches to a nipple on the block, you don't.  I'm having trouble remembering if an 87 would have a stat, but I know my 92 did.

Don't stress about the water pump.  If its pumping, it's good.  They are ridiculously simple rubber vanes in a brass housing inside the lower unit right where the plate is above the prop.  They do fail, and some people replace them every year to be safe, which I find equatable to changing the oil in your car ever day.  I boat far more than the average person.  As in, 3-4 times a day for 3 months of the year.  I live on a lake in the summer, and boating is my life.  Having said that, I have a 1960 Evinrude 10hp that has been in use on that lake since 1960.  My grandfather bought it, my dad inherited it, I abused it, now my nephew abuses it.  To the best of my knowledge, the water pump has never been replaced.  To the best of my recollection, here is the rest of the fleet and their water pump history:

1968 Merc 65: Never.  It went until the late 80s and dad had to replace a prop seal.  He thought it would be wise to do the pump, but the bi-metal corrosion was so bad he couldn't get the bolts out to remove the lower unit.  Rather than risk breaking something, he just left it alone.

1988 Merc 70: Once.  Not because it had failed, but because we had the whole thing rebuilt a couple years ago.

1967 Evinrude 6:  Once.  It sat in storage for about 10 years and my nephew wanted to revive it.  He decided to check compression while it was dry.  The rubber had fused to the brass and it damaged the tips of the fins.

1992 Merc 25: Never.  I have no idea how many hours were on that motor when I sold it, but it was a LOT.  It sat for 3 years before I sold it and when I fired it up, it pumped fine

mid-80s Johnson 48 special: Never.

The secret is to never spin the crank unless the pump is wet.  Although, my neighbor at the lake does it every year.  He uncovers it in the spring and fires it up dry on the trailer for a few seconds just to be sure it runs, and I don't think he has ever replaced a pump.

Use sta-bil, don't use sta-bil, it won't matter.  In this situation, I will (shocker) go along with the recommendation to use non-ethanol fuel.  The rubber in that older engine will start degrading with ethanol.  It won't hurt to run one or two tanks through it.  It's not like the damage is done immediately, its slow, and the worth thing that will happen is it will start sloughing off flakes of rubber from the inside and clog jets.  Replace the fuel lines with newer ethanol-compatible rubber, clean out the carb, now you can run ethanol fuel forever.  Using sta-bil is GREAT for preserving gasoline, but many of the formulations contain ethanol.  I never understood why people go to such great expense and trouble to buy ethanol-free gas, then put ethanol in it to stabilize it.  Here's what I do:  Run it out of gas (including the line from the tank) and tilt it down so the water runs out.  Done.  Stuff the boat in a field with a tarp over it and walk away.  In my I/O, I don't even run it out of gas.  I drive it on the trailer and turn off the key. Period.  Take it home, open the block and manifold drains, and walk away.  For the last 15 Springs, I put earmuffs on the inlet, turn the key, and it fires up.  No sta-bil, no ethanol-free gas, nothin.

Fogging the engine (which is more or less a process of shooting a preservative in the carburetor until the motor dies) is a fine idea, but IMO it's overkill.  The current 1988 70hp Merc on dad's boat has endured the same abuse I have given mine, and after 30 years it finally had enough compression loss that we rebuilt it.  We're talking WOT runs to the other end of the 13-mile lake for bass fishing in the morning, a 3-4 hour lake day with lunch and skiing, then a 3-4 hour evening trolling for walleye where it idles for hours at a time.  The full gamut of every possible abuse you can give it for 30 years.

One thing I always do.  Before freezing weather arrives, I always drain my lower unit oil.  If you developed a leak during the boating months and there is water in there, it likes to make rusty, freezy, breaky things happen.  If you live where it doesn't freeze, I at least let pull the drain for a few seconds to check for water/milkshake.  Nice to know that in the fall while you have time to fix it.  To ensure that the drain/fill plugs aren't the cause of the leak, get new plug gaskets.  They're cheap.  Like a few cents cheap.  I am totally in the habit of a complete drain, but if you haven't established a habit, notes are a good thing.  If I do something that is outside my normal habit, I will open my calendar app and set a reminder for May 1st that says "lower unit not drained Merc 70" or something.  Dad has a bunch of those little tags with wire twisties on them and he'll write down what the status is and tie it to the steering wheel.

Otherwise, pull the cord, abuse the heck out of it for 20 more years, and have fun.

drsmooth
drsmooth HalfDork
10/26/20 1:28 p.m.

Thank you to everyone! I learned alot in partucular Curtis73 if you type like I do that must have taken a few hours to put all that "to paper". 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/26/20 2:20 p.m.

voice to text is amazeballs.

PS... when running the gas out of the carb or the fuel line, you'll likely need a key, a screwdriver, or a pencil/pen to hold the check ball open.  In the end of the nozzle there is some form of valve (early Merc had a pin you pushed, later had a brass ball/spring/o-ring).  I like to stand up so the fuel follows gravity and every 30 seconds or so relieve the vacuum in the hose by pressing on it.  Expect it to take a while.  Those little things sip fuel.

drsmooth
drsmooth HalfDork
10/27/20 12:43 a.m.

In reply to Curtis73 (Forum Supporter) :

Expect it to take a while.  Those little things sip fuel.

You are bang on about that. I took it out today, hoping to empty out the tank for winter and barely made a scratch. After 2 hours of running I burned up about 1/4 of a tank on a 5 gallon tank.

That being said, I was only able to run it at partial throttle unless I had big stretches of open water in front of me. The bow rose so high I couldn't see what was ahead so I had to slow down. Next Step Hydrofoil!

One thing I didn't account for was the boat. The boat is a 60's era fiberglass boat that had 4 seats, a huge cap of fiberglass and a windshield on the front. As well as a driving position at the front right (starboard) position on the boat. The thing probably weighed 500 pounds when I got it including motor 33hp seahorse BTW.

I gutted the boat and made it tiller controlled. If you started with a watermelon cut it in half lengthwise, scooped out all but the rind, then added wooden seats, that sums up this boat. 

Funny enough, with all the weight taken out in a straight line at least, it is faster than the 33hp it replaced. I am going to have to get a hydrofoil to keep the front down!

 

03Panther
03Panther Dork
10/27/20 2:29 a.m.
Curtis73 (Forum Supporter) said:

voice to text is amazeballs.

I had never heard that "word" used... till last week - watching a Miliy Cirus movie. (can we say REALLY bored?) It was used. A lot. It was bad. Very bad.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/27/20 9:34 a.m.

In reply to 03Panther :

Amazeballs.... amazeballs.... amazeballs.

And just for added emphasis, I'll thow in a MOIST.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/27/20 9:38 a.m.

In reply to drsmooth :

Other things I sometimes do is to get an extended fuel hose and then stash the tank, anchor, and other things up front.  I have a skinny "rooftop" 14' v-hull aluminum boat with a 9.9 Johnson.  Even with all that stuff in the front and the trim pin removed, it skates on the very back few inches of the hull.  I can see OK because it's such a shallow boat, but I'm still porpousing all over the place with my fat butt in the back alone.  The tiniest breeze sends me on a new course.

I actually gave that 9.9 to my nephew and put a 6hp on that boat.  Slower, but fewer white knuckles.

mtn (Forum Supporter)
mtn (Forum Supporter) MegaDork
10/27/20 10:27 a.m.

We have a 14 foot Lowe aluminium, with a floor for the back 2/3 of the boat and a 9hp Yamaha 4 Stroke. It is quite underpowered, great for trolling, but if you're trying to get somewhere it is slow going.

We actually installed trim tabs because if you were by yourself, you could either troll at about 1-3 knots, or you could have the bow so high that you couldn't see. It is a huge improvement but still isn't great, to the point that I want a tiller-handle extender. It is fine with another person in the boat, but otherwise it is just too much weight in the back of the boat.

drsmooth
drsmooth HalfDork
10/27/20 11:27 p.m.

In looking up how to keep the bow down, i have come across a number of hydrofoils or insert name of similar product here. Anyone know if there is one that is adjustable? All of them bolt to the lower unit, but all of them seem to be fixed angle. Which rely on the adjustability of the motor.

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) MegaDork
10/28/20 9:33 a.m.
drsmooth said:

In looking up how to keep the bow down, i have come across a number of hydrofoils or insert name of similar product here. Anyone know if there is one that is adjustable? All of them bolt to the lower unit, but all of them seem to be fixed angle. Which rely on the adjustability of the motor.

Correct.  All of the ones I've seen that bolt on the cavitation plate are fixed.  They are meant to amplify whatever the trim position is.  If you're trimming up to lift the bow, it adds downforce at the back.  If you trim it down, the foil points up a little and causes lift at the back.

Is yours one of the red-tops?  Like Sears, Sea King, or Crestliner?  One of the things you're fighting is the fact that it used to be a runabout, so it was designed to have a CG based on the front hood and passengers in the middle.  I have an aluminum runabout from 1958 that kept pulling the throttle cable out of the jacket.  I zip tied it, but it would pop out sometimes.  So I would put a milk crate beside the motor to operate it as a tiller when that happened.  Even with the hood and windshield still on, I couldn't see over the front and it didn't like to plane.

I would consider maybe shifting as much weight forward as possible to help first.  Try to help it plane by simulating the right CG.  Right now the hull is fighting the water by the bow being pushed too high, and adding a foil will fight it in the opposite direction and add unnecessary drag.  The best trim is trim you don't need to make, if that makes any sense.

mtn (Forum Supporter)
mtn (Forum Supporter) MegaDork
10/28/20 10:06 a.m.

The easiest and cheapest thing will probably be a tiller extender and sitting in the middle, like Curtis is suggesting. Move the weight to the front.

drsmooth
drsmooth HalfDork
10/28/20 8:14 p.m.

In reply to Curtis73 (Forum Supporter) :

I will try your plan out and move as much weight as i can to the front. 

Not really sure the original make of the boat  but it was definately late 60's era based on the style and the motor that came with it  (I should have taken a before picture). 

drsmooth
drsmooth HalfDork
10/28/20 8:18 p.m.

In reply to mtn (Forum Supporter) :

I may still have a tiller extender laying around from my old trolling motor. I love it when my junk becomes usefull again. Only problem it it encourages me to keep junk around!

You'll need to log in to post.

Our Preferred Partners
icfFM3PtuODhOkf4F2IxCvWaEJUiLO8x5efpiQ3OBc9cYCFtXLZL0eSBhrP8UGin