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Help with an older Mercury Outboard #4440116
06/24/17 07:04 AM
06/24/17 07:04 AM
Joined: Apr 2008
Posts: 25
Northern California
Trigger Offline OP
Trigger  Offline OP
Joined: Apr 2008
Posts: 25
Northern California
My son just acquired an older ski boat with an outboard Mercury motor on it and I have no idea on anything about the motor. I was hoping someone here could give me some advise. It is a late 70's or 80's ski boat. The engine is a Mercury 140HP. I know it is a two stroke, six cylinder. It is also marked Thunderbolt Ignition. The serial number is 3754838 if that helps anyone.

So I have no idea where to get any parts and don't even know what the oil ratio is. An internet search really did not help. Everything seems to default to a 150HP motor. If anyone can give me advise as to what model this is, where to find parts (Plugs, Impeller, ect.) and what the oil ratio is, I would really appreciate it. Oh yeah, it also has not run in about 5 years, but was told that it ran like a top when parked.

Thanks,
Travis

Re: Help with an older Mercury Outboard [Re: Trigger] #4440120
06/24/17 07:10 AM
06/24/17 07:10 AM
Joined: Sep 2003
Posts: 5,805
Waterloo, ON
Bluestream Offline
Bluestream  Offline
Joined: Sep 2003
Posts: 5,805
Waterloo, ON
You can buy parts at a Mercury dealer, or online at many places like:

https://www.marineengine.com/

https://www.marineengine.com/parts/mercury-outboard-parts/140

Mix ratio is 50:1

Last edited by Bluestream; 06/24/17 07:12 AM.

2000 VW Beetle 1.8T M5
2006 Pathfinder 4X4
1991 BMW 735iL
"A fool and his money are soon parted" - Thomas Tusser
Re: Help with an older Mercury Outboard [Re: Trigger] #4440123
06/24/17 07:14 AM
06/24/17 07:14 AM
Joined: Apr 2007
Posts: 3,001
WI.
dblshock Offline
dblshock  Offline
Joined: Apr 2007
Posts: 3,001
WI.
beautiful engine, would be $25k if available today.


16 Civic Coupe Touring 38k
640:1 TCW-3 E091
Edge 0/40 XG7317
Firehawk Indy 500

06 4Runner SR5 146k
640:1 TCW-3
PP 5/30 XG3614
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Re: Help with an older Mercury Outboard [Re: Trigger] #4440130
06/24/17 07:26 AM
06/24/17 07:26 AM
Joined: Sep 2009
Posts: 2,167
Deep in the heart of Jersey
BigCahuna Offline
BigCahuna  Offline
Joined: Sep 2009
Posts: 2,167
Deep in the heart of Jersey

Re: Help with an older Mercury Outboard [Re: Trigger] #4440132
06/24/17 07:28 AM
06/24/17 07:28 AM
Joined: Mar 2004
Posts: 21,123
Upstate NY
Donald Offline
Donald  Offline
Joined: Mar 2004
Posts: 21,123
Upstate NY
So possible fuel issues in tank and carb. Drain lower unit gear oil, look for water, use Mercruiser premium gear oil at Walmart.

Change plugs.

Get new impeller kit from Merc dealer.

I would guess it's 50 to 1 ratio.

Thunderbolt is Merc name for it's breaker less high voltage ignition.


2015 Subaru Forester 2.5 engine/CVT
2015 Ford F250 w/Powerstroke
2016 Subaru Crosstrek CVT (wife's)
Re: Help with an older Mercury Outboard [Re: Trigger] #4440156
06/24/17 07:56 AM
06/24/17 07:56 AM
Joined: Sep 2014
Posts: 1,490
Toronto Canada
WobblyElvis Offline
WobblyElvis  Offline
Joined: Sep 2014
Posts: 1,490
Toronto Canada
I have a service manual for older mercury outboards. I think it only covers the 6 cylinders up to 110 hp. The manual is seen here.https://www.amazon.com/Mercury-Outboards-Service-Manual-C-90-68647/dp/B00130F6K0

You can have it if you like for just the cost of shipping.

Re: Help with an older Mercury Outboard [Re: Trigger] #4440252
06/24/17 09:53 AM
06/24/17 09:53 AM
Joined: Sep 2015
Posts: 6,080
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline
Joined: Sep 2015
Posts: 6,080
Kalifornia Kollective
Good motor. Sometimes a bit of cooling issues with top 2 cylinders. Need to go through cooling system and make sure all is good. Prolly change thermostat ...

This is a good forum to discuss Merc issues: http://www.fiberglassics.com/forum/mercury-outpost.html

These motors are sought after by the go-fast crowd. If you want to find out how to hot-rod them, the boards at Scream & Fly will help you sort out rigging, weight distribution, prop'ing, etc. You can ask here: http://www.screamandfly.com/forumdisplay...1bdc60cf5cba404 laugh


Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: Help with an older Mercury Outboard [Re: Trigger] #4440273
06/24/17 10:32 AM
06/24/17 10:32 AM
Joined: Aug 2003
Posts: 11,014
Buffalo, NY
JTK Offline
JTK  Offline
Joined: Aug 2003
Posts: 11,014
Buffalo, NY
Coolest looking OB motors ever IMO. Sound great too. I've never owned one, but fuel consumption has got to be horrific.


2017 Ram 1500 4x4, 3.6L. 2016 Nissan Quest SV (Babe magnet IV)
Re: Help with an older Mercury Outboard [Re: Trigger] #4440276
06/24/17 10:40 AM
06/24/17 10:40 AM
Joined: Oct 2008
Posts: 19,206
Sunny Florida
SteveSRT8 Offline
SteveSRT8  Offline
Joined: Oct 2008
Posts: 19,206
Sunny Florida
I used to own a 135 six banger on a 17 foot Cobia. GREAT engine. The 115 and the 135 were nearly the same except for carbs. Actually did very well on fuel for the day. Good ski motor with a smaller prop, too. Ran 52 mph in a measured mile on the Indian River. In these older 2 stroke engines the mixing of fuel was critical, if you do it right there is little to no smoke!

We ski'd all day on 12 gallons, fuel was like 39 cents at the marina...


"In a democracy, dissent is an act of faith."
J. William Fulbright
Best ET-12.79 @ 111 mph
4340 pounds, Street tires
Just like we go to Publix
Re: Help with an older Mercury Outboard [Re: Trigger] #4440307
06/24/17 11:36 AM
06/24/17 11:36 AM
Joined: May 2006
Posts: 4,045
Central Wisconsin
dwendt44 Offline
dwendt44  Offline
Joined: May 2006
Posts: 4,045
Central Wisconsin
Quote:
The 115 and the 135 were nearly the same except for carbs. Actually did very well on fuel for the day


The exhaust porting is significantly different between the two.
The in-line six had a rep for being gas hogs. Not sure if that was
true or not.

My 2


There's no such thing as:
Too big of a battery,
Too large of a gas tank,
or too loud of a horn,
or too bright headlights.
Re: Help with an older Mercury Outboard [Re: Trigger] #4440354
06/24/17 01:01 PM
06/24/17 01:01 PM
Joined: Apr 2008
Posts: 25
Northern California
Trigger Offline OP
Trigger  Offline OP
Joined: Apr 2008
Posts: 25
Northern California
Thank you for the great responses. I checked out some of the links you guys sent and they did not seem to recognize my serial number. I'll get to digging around it and try to find another number. Thanks again to all of you!

Re: Help with an older Mercury Outboard [Re: Trigger] #4440489
06/24/17 04:34 PM
06/24/17 04:34 PM
Joined: Sep 2015
Posts: 6,080
Kalifornia Kollective
BrocLuno Offline
BrocLuno  Offline
Joined: Sep 2015
Posts: 6,080
Kalifornia Kollective
The Merc guys at Scream & Fly have these things figured out very well. Start a "newby" thread there about your motor and include a picture. They will all jump on it and offer all sorts of advice and sources smile


Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.
Re: Help with an older Mercury Outboard [Re: Trigger] #4442175
06/26/17 05:16 PM
06/26/17 05:16 PM
Joined: Feb 2009
Posts: 67
ny
jeep58 Offline
jeep58  Offline
Joined: Feb 2009
Posts: 67
ny
If you go to a site called Iboats.com go to mercury section you will find out all you need to know.

Re: Help with an older Mercury Outboard [Re: BrocLuno] #4443293
06/27/17 09:58 PM
06/27/17 09:58 PM
Joined: Jun 2003
Posts: 1,963
Sequim, WA
edhackett Offline
edhackett  Offline
Joined: Jun 2003
Posts: 1,963
Sequim, WA
Originally Posted By: BrocLuno
Good motor. Sometimes a bit of cooling issues with top 2 cylinders. Need to go through cooling system and make sure all is good. Prolly change thermostat ...

This is a good forum to discuss Merc issues: http://www.fiberglassics.com/forum/mercury-outpost.html

These motors are sought after by the go-fast crowd. If you want to find out how to hot-rod them, the boards at Scream & Fly will help you sort out rigging, weight distribution, prop'ing, etc. You can ask here: http://www.screamandfly.com/forumdisplay...1bdc60cf5cba404 laugh


Yes, wonderful motors. The cooling issue is air getting trapped in cooling jacket at the top. The fix is to install a fitting in one of the bosses in the upper cylinder and plumb that to the tell tale. That keeps the air purged.

Here's a picture of one being used in anger this morning. It's one of Doc Frankenmerc's motors on my brother in law's homebuilt speedster. What a great morning we had, except I got kicked out to take pictures. Speed was a few mph under the top speed of 60 mph to date. It's a 100 hp hiding under an older 80 hp cowling.



Never attribute to engineers that into which politicians, lawyers, accountants, and marketeers have poked their fingers.
Re: Help with an older Mercury Outboard [Re: edhackett] #4443637
06/28/17 09:11 AM
06/28/17 09:11 AM
Joined: Oct 2014
Posts: 12,582
Idaho
CT8 Offline
CT8  Offline
Joined: Oct 2014
Posts: 12,582
Idaho
That is what an out board engine is supposed to look like ! The underneath of that boat looks dry grin . She is very pretty.


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2018 Ford F350 6.2
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