Search Results for 'mercury mark 55'

[crosbyman]

most condensers fail eventually   can you do basic test…(short – open – capacity kick or measurements )   some mercs have tricky “insulating blocks” in the ignition system so check for airline cracks which could allow shorting out sparks

check spark wire continuity from plug boot back to ignition coil (s)  see chatgpt info

Step-by-step servicing procedure

1. Access the magneto / points

   • Remove cowl and any retaining hardware, then pull the flywheel (use a flywheel puller). The breaker points and condenser are usually mounted under/around the flywheel on these 1950s Mercury units. aomci.org

2. Visual inspection

   • Look for oil/water contamination on the points or condenser, cracked insulation on HT wires, corroded connections, or arcing marks. If the points heel (the fiber pad) is badly worn or the faces are pitted/blue, replace the points. maxrules.com

3. Clean or replace points

   • If only lightly dirty, clean the contact faces with a points file or fine emery, then wipe with contact cleaner. If pitted or rough, fit a new points set. Setting the gap is critical (see step 5). MarineEngine

4. Replace condenser (capacitor)

   • Condensers commonly fail after decades; replace with a modern equivalent sized/voltage-rated for magneto use. Replacements are readily available from vintage parts suppliers — don’t risk a weak condenser (causes weak or no spark). Smokstak+1

5. Set the points gap (pre-timing)

   • Typical magneto/points guidance for vintage outboards: about 0.012″–0.018″ (0.30–0.45 mm) is commonly used. Many restorers set ~0.015″ (≈0.38 mm) as a safe target, then fine-tune timing. Small changes in gap change ignition timing — set the gap first, then time the magneto. Use a feeler gauge at the maximum cam lift (follow the manufacturer method if you have the manual). themagnetoguys.co.uk+1

6. Lubricate the cam / pivot

   • A tiny smear of distributor/cam grease on the rubbing block/cam contact prevents rapid wear. Don’t over-grease where it can fling onto electrical contacts. oldcroak.com

7. Check coils and wiring

   • Use a multimeter to check primary/secondary resistance of coils (if you have coil specs from a manual). Inspect HT leads and caps for cracks; replace if brittle. If coils are open or shorting, they’ll need rebuilding/replacing or a professional magneto service. aomci.org+1

8. Timing

   • With the points gap set, reinstall flywheel enough to rotate by hand and observe when the points open (or use a strobe/timing light on running motor if possible). Many vintage Mercury setups require firing roughly at a point before TDC — manuals/forum threads explain the exact advance angle for each model. If you don’t have a timing mark, set the gap with the cam high-point method then fine-tune on the test tank. aomci.org+1

9. Test firing

   • Reconnect HT leads (or reinstall plugs), turn the engine over by hand to confirm sparks at each plug (use a plug removed and grounded safely to check spark visually), then run on a test tank with proper choke/throttle adjustments to check idle and advance behavior.

10. If things still misbehave

• Common causes after a points/condenser service: wrong gap, weak condenser, cracked coil insulation, magneto assembly seating (flywheel key/fit), or advance mechanism mis-set. Forum rebuild threads and magneto-specialist videos walk through diagnostics—mail-in magneto rebuilders exist if internal coil or cam ring work is needed. aomci.org+1

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Replacement parts & repair services

• Where to buy parts: OldMercs, MarineEngine parts listings, eBay listings for vintage points/condensers. Match by model/serial if possible. oldmercs.com+2MarineEngine+2

• Magneto rebuild shops / specialists: Many restorers refer to small specialists (mail-in) or local antique outboard shops — forum threads list names and experiences. If coils are bad, specialist rewind/repair is usually required. aomci.org+1

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Quick troubleshooting checklist

• No spark at all: check condenser first, then coil continuity, then points opening.

• Weak, intermittent spark: dirty points, leaky condenser, cracked HT lead.

• Timing oddities after changing points: re-check gap and re-set magneto position; small gap changes = a few degrees of timing shift. Smokstak+1

 

 

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[labrador-guy]

What kind of grease should I be using on the shift cam on  1956 mark 55?  It takes a lot of muscle to get’er into reverse.  I been using regular marine grease.  Once it’s in gear it works like it should.  Gear oil is OK.  Maybe it needs lubraplate?

dale

get’em wet….don’t let’em set

[labrador-guy]

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[Russell Bardak]

Hello,

I finally am getting around to restoring my lapstrake boat and outboard.  I have a Mercury Mark 25E.  Here is a photo of the coils:

Here is a close-up of one of the coils:

My question is, does anyone have a line on replacement coils?  Please let me know.

Russell

[Shell Kottkamp]

Interesting thread.  I noted olcah comment about the 1954 model electric start powerhead having a different casting, i.e., threaded studs, to allow for the starter bracket.  I had a similar experience with what I thought would be an easy electric start conversion with a Mercury Mark 25,  I went into that project with my eyes wide shut!  The 2 years, 1955, 1956, Mercury produced that electric start model it also had a dedicated powerhead with 4 threaded studs to allow for the starter bracket.   For kicks and giggles I have considered drilling and tapping the 4 studs in a standard Mercury Mark 25 powerhead for an electric start conversion.   I love the convenience of electric starting.  I’ve done several 1957/1958 J/E 18hp conversions and they couldn’t be easier.  It was interesting reading today about the early, (1954), OMC history  of electric starting.

[outbdnut2]

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[Tubs]

outbdnut2 wrote:

The dents, the rope, the silicone RTV,  faded decals and paint…..that stuff is “Patina”……gives the motor “Character”! ….a lot of that is being left on some old cars in that hobby now – just a quick wash and spray clear paint over the whole mess!   Some car clubs have awards for patina on unrestored “survivor” cars.  Maybe AOMCI needs to have a class like that??!! (LOL!).

Dave

 

I try to get every motor running and use them some in the summer. That is the intent for this cub. The OA-55 has more issues than dents in the gas tank and being dirty. It might make it to the lake in 26. I’ll post pictures when I get into it. I also like to detail motors. Some to a higher standard than when new. I have a nice 1953 Mercury Mark-7. It does have some scratches in the paint of the gas tank but the motor is too original to restore. https://youtu.be/rXy43dZuPNg  And I have what would be called a “RAT” motor in the car & bike circles. It perfect as is and will never be restored as long as I have it. Here is a video link for those who may be interested and haven’t seen it.  https://youtu.be/lJ6cXeWWi7g  

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[Tubs]

outbdnut2 wrote:

The dents, the rope, the silicone RTV,  faded decals and paint…..that stuff is “Patina”……gives the motor “Character”! ….a lot of that is being left on some old cars in that hobby now – just a quick wash and spray clear paint over the whole mess!   Some car clubs have awards for patina on unrestored “survivor” cars.  Maybe AOMCI needs to have a class like that??!! (LOL!).

Dave

 

I try to get every motor running and use them some in the summer. That is the intent for this cub. The OA-55 has more issues than dents in the gas tank and being dirty. It might make it to the lake in 26. I’ll post pictures when I get into it. I also like to detail motors. Some to a higher standard than when new. I have a nice 1953 Mercury Mark-7. It does have some scratches in the paint of the gas tank but the motor is too original to restore. And I have what would be called a “RAT” motor in the car & bike circles. It perfect as is and will never be restored as long as I have it. Here is a video link for those who may be interested and haven’t seen it.  https://youtu.be/lJ6cXeWWi7g  

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[Sam55]

Hello can anyone offer instruction on a 1955 Mercury Mark 6 comet twin Impeller change? Specifically, where and what has to be disconnected in order to drop the lower unit. Thanks.

[SHELL KOTTKAMP]

Greetings Dave.  I also have a 1955 Mercury Mark 25 electric start and would also rather install a Delco starter as opposed to the “swing away” starter given it’s more reliable and easier to install, (plus the 1955 is a positive ground starter).  The issue with the 1955 model is the Delco starter given it’s design won’t fit given the top of the 1955 model uses a standard Mark 25 recoil/top, the 1956 model had a different cast top designed for the “taller” Delco starter, also the port side cowling of the 1955 may not clear the Delco starter.  Only answer I see with using the Delco starter on a 1955 is to gently remove enough material on the aforementioned side cowling and the top to make clearances for starter.  Always appreciate your thoughts on these Mercs.  Shell in Oregon.