Two Mercs

"Hi. I've got a 20 merc E

"Hi. I've got a 20 merc Electric start, serial 4710763, that I think is a 1977. It's only running on one cyl (not sure which one). A tech told my late dad that a coil is gone, and that it would be expensive/nearly impossible to get a new one. I see that coils are available (part 3995288A2, followed by 24 99). Is there a way to check the coils, and is there anything else that may cause the no spark? (other than the obvious..I've checked wires, changed plugs, etc). I also have a merc 18 XD, serial no 7218344, that I think is a 1985. What does the XD stand for? I was given this motor, and know nothing about it, where the 20 has been in the family since new. Also, are these mercs, yamis, or what have you?
Thanks in advance"

"1. Sorry about Dad. Lost min

"1. Sorry about Dad. Lost mine, then my father-in-law as well, only two weeks apart.

2. Coils for that motor are dirt cheap and common as hell! That "expert" is nuts. Hell, I'll even send you one--FREE. (E-mail me direct with your address.)

3. The "XD" was pure advertising crapola far as I can see. No noticeable difference in the motor's running or power.

Jeff"

"Thanks for the kind words and

"Thanks for the kind words and the offer of the coil Jeff. I will send you my address. I kinda thought there might be something to the XD thing, maybe a lower gear ratio to turn bigger props, or something like that. And yeah, that merc mechanic(???) was a jerk. Anyways, I'm pretty sure the 20 is a merc, with the thunderbolt ignition system and all, but I'm not sure about the 18. I can't find it listed in any of the online sources I've looked at so far.

thanks again
Bill"

"The 20 Mercs had the Thunderb

"The 20 Mercs had the Thunderbolt 4 ignition (that's the common one with lots of parts on the market) since the early 70's.

The 18XD which was a detuned 25XD (which later simply became the 25) also had a T4 ignition.

The XD models (which meant nothing as Jeff notes) were discontinued after 1985 (whole new line-up came out for the 86 model year).

Your 18 shares an ignition with the 86-on 6/8/9.9 and 15 horse models as well as the 25's.

Actually a decent little motor that put out about 22 horses.

Given a choice between the two of them, personally I would opt for the 18 horse model..."

Thanks for the info Graham..I

Thanks for the info Graham..I like the 20 for it's electric start. Is the 18 XD a merc or yahmi??

Both!

Jeff

Both!

Jeff

"Jeff is correct. The powerhea

"Jeff is correct. The powerhead and gears are built by Yamaha (but the powerhead was produced specifically for Merc and was not used by Yami in their own branded motors).

The ignition, gearcase and every other small part is Merc - the best of both worlds.

The 20 Merc was always an orphan no matter what model run it was. It never shared a block with any other motor (rare for a Merc).

I suspect the comments you got from the "tech" were a misinterpretation of something he heard.

The slightly older 20 horse Mercs with the T2 ignition have points that are long out of production (and about as common as hens teeth) which make the ignition very undesireable, however, your model is completely supported by Merc and the aftermarket as far as coils/stators/triggers are concerned."

Good to know that parts are av

Good to know that parts are available. Why would they detune a 25 to turn it into an 18?? Was it to fill a gap because they wern't making/selling a 20 in that generation? What might be involved in turning it back to a 25? I've got a ridiculously heavy 16 foot aluminum hull to put it on.

"Merc stopped producing the 20

"Merc stopped producing the 20 (formerly model 200) after the 1981 model year and detuned the 25 (to 18 horses) to fill that gap (since then didn't produce a 15 horse then either so it went right from 9.8 to 18 horses with nothing in between).

In 1986 they reintroduced the 20 using the block from the 18XD(so they really just changed the stickers on the 18XD and called it a 20 and lauched it with the new 6/8/9.9 "portable" line which added the 15 horse in 1987).

My earlier comment about the 20 not sharing a block was only partially correct.

In later years before it was phased out the 20 did share a block with the model 15XD and 25 SeaPro and Marathon models, but those were well after your model and a number of other changes had been made...

Yours will have the 21.something cubic inch block which last saw production in 1981."

"Sorry, missed your last quest

"Sorry, missed your last question. To turn your 18 into a 25 just need to swap out the carb - all else is the same.

I would only suggest the upgrade if you can find a used carb from a 25 at a super cheap price.

It takes a 50% increse in horsepower to get a 15% performance increase on any given hull (boat).

Your 18 is already putting out between 20-22 horses (until the EPA got their fingers on outboards, Merc drastically under-rated the horsepower of their motors so they would outperform in comparative tests with OMC).

But even if it was putting out exactly 18 and you upped it to 25 (about a 40% increase) you may only see a 1-2 mph increase at top end and nothing at the lower end since the torque band would remain unchanged until you exceeded 5000 rpms.

However, when compared against your 20 horse, the 18 with it's 24 cube powerhead will actually produce more torque to get your heavier boat going and on plane compared with the smaller displacement 20.

So in the end my advice would be "if you are keeping your current motors, don't fiddle with them, just live within their limitations" OR sell the pair of them and try and get ahold of a 4 cylinder 30 or 40 horse 1980-something Merc which will really push your 16 footer along nicely..."

"Hmmm... Things are starting

"Hmmm... Things are starting to make sense now. I was given the boat and 18 together. The previous owner told me that the 18 moved it along pretty good, and that he had the large boat for playing around in Georgian Bay. I haven't had either one wet yet, but this year I will, cause my 50 Evinrude package is really showing it's age (1971). Once I get the 20 fixed, I'll try them both and see which one works better."

"Back about 100 years ago when

"Back about 100 years ago when I was a kid we had a cottage near Victoria Harbour.

I spent many a day out on a 14 foot Peterborough (mahogany plywood runabout) being pushed by a 40 horse Gale (which is currently in my basement and by today's standards produces about 35 horses) on Georgian Bay.

You wouldn't catch me out on water that big today with a little, low powered boat like that - and probably why all my hair is white

Either the 18 or the 20 should (push) her around fine to do a bit of fishing, but if you personally plan on using it on some bigger water, I really would look at a motor upgrade.

What is the boat made of? A 16 foot aluminum would be almost too much for 18/20 horses, if it's another material you really are under powered.

I run a 14 foot Princecraft (utility) that I added a full console to (built with marine lumber - starboard).

My dry hull weight was 220 pounds. With the console, motor(s) - run a 2.5 horse twin cylinder "kicker" because I won't leave the dock with only 1 motor, battery and other gear plus me and the wife she displaces maybe 750 pounds.

I push that with a 15 horse Merc/Mariner and get top speeds of about 22 mph (35 kph) in calm water. That is fine for the small lakes in the Kingston area where I am, but certainly wouldn't venture out any distance from shore on bigger water and have to worry about the weather.

My point being, a 16 footer may feel like a big boat (relative to others in it's class), but low horsepower can make it dangerous, so try it out somewhere safe...."

"Small world Graham..the boat

"Small world Graham..the boat and motor came from Victoria Harbour. It's a 16 foot deep V Springbok aluminium, really heavy duty, and it weighs more than I want to think about. I'm thinking of fixing the 50 Evinrude (probably just a carb rebuild needed) and putting that onto it. It would just be a hassle rigging up a console like you did on yours. Then I could get a smaller rig for either the 18 or 20."

"Ah, good oracle of Outboardin

"Ah, good oracle of Outboarding, the tuner of an 18 is MUCH more restrictive then that of a 25, as are the ports. The tuner can be swapped out to up the horsepower, but porting will still be required. As you stated, the carb is also very restrictive.

Jeff

PS: I know this is true from a friend of mine who did the actual measurements."

"Thanks Jeff, I was not aware

"Thanks Jeff, I was not aware of that. So they played the same game as the 9.9/15 horse models.

You can swap the exhaust plate on a 9.9 with one from a 15 and make it a 12 horse, but you also need the carb for a full 15 conversion (which Merc did themself in the 04/05 model years and sold them to outfitters).

I wasn't aware that they actually tooled the two models separate (the 18/25), which kinda seems like a waste of time - but anyhow....

Thanks for info - I will put that one away for future ref..."

"Jeff.... You've just got

"Jeff.... You've just got to get a picture of you in a bigger boat. Every time I spot that small craft speeding along, all I see is Forest Gump (grin). Hope that all have a Merry Christmas and a safe and Happy New Year.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"

"Merry Christmas, Joe!
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"Merry Christmas, Joe!
"

Old thread, I know.
Have a quick question for you experts.
A guy wants me to take his boat in trade for some work on his house.
20 Mariner.
Serial number: A161721 (1985 I believe)
Does the informative discussion above apply also to Mariner engines?
Yamaha power head? T-4 ignition? Actually pushes 22 horse? Parts easy to find? etc.
Many thanks!