1985 60 HP Mercury Cylinder #3 not firing

[solarismike]

New to boating. Bought a Marshall Trihull 15 ft with 60 HP Mercury. PO said it had been out of the water for about a year. Carbs look great inside following a little seafoam treatment. First trip out would only run in lower speeds. Running up throttle caused engine to "bog out" and stall. Today the engine simply stalls when put into forward gear. I determined that the lower cylinder is not firing. Swapped coils, no change. It does have spark but pulling the plug results in no change. Thoughts?

 

[jimmbo]

Bad Plug. Bad wire(s). How did you do the "SeaFoam Treatment"? Spraying into the carbs really does Squat, other than clean the throttle plate. There are other carb cleaners that are much better than light oil.To get those carbs clean internally they need to come off and come apart.
Actually the first thing you need to do is a Compression test. Then a spark test, can the spark jump a 3/8" gap? after that, the fuel system.

 

[racerone]

cylinder needs 4 things to run----Spark at the right time.-----Fuel.-----Compression in the cylinder.----Compression in the crankcase.------You say there is spark.----More trouble shooting needs to be done here.

 

[solarismike]

Bad Plug. Bad wire(s). How did you do the "SeaFoam Treatment"? Spraying into the carbs really does Squat, other than clean the throttle plate. There are other carb cleaners that are much better than light oil.To get those carbs clean internally they need to come off and come apart.
Actually the first thing you need to do is a Compression test. Then a spark test, can the spark jump a 3/8" gap? after that, the fuel system.

Thank you for the quick response! Much appreciated!

Half a can of Seaform was added to 6 gallons of gas. I burned through 5 of that puttin' around in the lake at top speed it would run which was a fast idle. I have pulled the carbs, they are shiny clean and all ports/jets are clear. Plugs are brand new yesterday. I will be obtaining tool for compression testing today. Also will be trying to test strength of spark.

 

[solarismike]

cylinder needs 4 things to run----Spark at the right time.-----Fuel.-----Compression in the cylinder.----Compression in the crankcase.------You say there is spark.----More trouble shooting needs to be done here.

More data... Compression testing yields 130, 110 and 122 for 1,2, and 3, respectively. On startup, I found that all cylinders were firing, as demonstrated by spark wire pull off, with the choke on. Warmed up, backed off the choke and the symptoms reappeared. Looks like a fuel issue with cylinder 3. Spark is noted to jump 3/8 inch gap. Hearing a crisp snap, snap, snap on all cylinders at that gap.

Three cylinders with two (2) carbs. Shall I pull the carbs for an ultrasonic treatment, or might it be an issue with the fuel/air mixture or tuning/synchronization?

 

[Steve212]

I was in a marine shop trying to figure out my overheating problem (welcome to boating) one of the mechanics just fixed an outboard after several hours looking for the problem (no sprk) turned out to be a short in none of the wires not directly related to that cylinder.

 

[solarismike]

Hello, I have 2012 cobalt with Volvo 8.1gic-q overheating. Help!! This is the 400 with cats.

I have changed the impeller, the thermostat, the sensor in the thermostat housing and in the back of the engine. I have good flow from the water pump, and freshwater system.

With and infrared thermometer I have checked the temp when it is running at low and high RPMs. Up to 1480 RPMs it stays around 150-165 (thermostat opens at 160. Over 1500 rpms it starts to overheat. The top of the port side head is the hot spot at 206 all hoses water pump and freshwater intake are 108-145. The exhaust is 185 and increases with run time 205 or so. I don’t let it get any hotter. Also engine goes into limp mode.

Looks like you inadvertently hijacked my thread. Likely you will get more specific attention to your issue with a specific new thread on your issue.... Good luck with your issue.

Edit: Now seeing your second post. Perhaps I misspoke. Sorry. Thanks for the insight.

 

[Steve212]

no you were right. Sorry about that. I thought I was posting. then I thought about the visit to the shop.
thanks and good luck to you as well.

 

[solarismike]

Update: So I may have resolved the issue. Going to head to a lake to validate.

It appeared to be an issue on the fuel side of the equation. Spark and compression was good. I found two things.

First I evaluated the functionality of the butterfly valves. Looks like I forgot to tighten the screw connecting the two butterfly linkages when I had the carbs out. This was a secondary issue that worsened the problem I was initially addressing.

What I believe to be the primary problem was the fuel/air needle valve was only 2/3's of a turn from seated. I backed then both out two full turns, and adjusted with idle at lowest possible to keep running in forward gear. Now it fires up immediately! Idles well. Combustion noted in cylinder three, and it throttles up well under load (though prop is just in a barrel).

Headed to the water in a few minutes for a more thorough evaluation. THANK YOU to all who contributed wisdom. ;-)

Update pending.....

 

[jimmbo]

Well you definitely do need to verify the sync between the two carbs as well as between the carbs and the timing. Two turns out is probably way too rich, but once in the water and under load, you can readjust. You might have to reset the idle speed, and the reset will also require an adjustment to the throttle cable length

 

[Texasmark]

As I recall carb jet setting is that the engine will just take the load when you hammer down on the throttle from idle.....like leaving the no wake zone and heading out. Idle setting for a lot of engines is 675 rpm give or take. Faster the idle harder it is to shift quietly (save gear wear and tear) but harder on the engine to respond if you have it set too lean.

 

[solarismike]

Update: Problems solved. The boat idles smoothly, run great, comes up on plane reasonably quickly. Motored around the lake for 1 hour and 50 minutes. Traveled 20+ miles according to GPS app. Top speed 31 mph, which I believe is reasonable for this old boat. Smooth all the way through the throttle range. All is good! Thanks for the help!

 

[solarismike]

Well you definitely do need to verify the sync between the two carbs as well as between the carbs and the timing. Two turns out is probably way too rich, but once in the water and under load, you can readjust. You might have to reset the idle speed, and the reset will also require an adjustment to the throttle cable length

Thanks for the insights. I have worked extensively on my collection of antique motorcycles. That experience helped a lot here. I think I finally got her dialed in. ;-)

 

[solarismike]

As I recall carb jet setting is that the engine will just take the load when you hammer down on the throttle from idle.....like leaving the no wake zone and heading out. Idle setting for a lot of engines is 675 rpm give or take. Faster the idle harder it is to shift quietly (save gear wear and tear) but harder on the engine to respond if you have it set too lean.

If you are new to boating or have a new boat, a knowledgeable friend could show you how to operate your boat and save you a lot of grief, maybe some money, and maybe your life.

I have a second cousin who has been a life long boating enthusiast and sold boats in Florida for 20 years. He had great insights. Did a trip on the St. John's river in Florida for his mentoring/advice for several hours. Worked in ER's for 20+ years as a registered respiratory therapist and have a deep appreciation for safety. BoatUS boating safety course completed before hitting the water. No chances to be taken with my grandkids in this equation. ;-) Thanks for the thoughts!

 

[solarismike]

How is the boat running now?

 

[solarismike]

Start up!

 

[solarismike]

[No message]

 

[jimmbo]

Sounds pretty good.