Martin 40 ~ 45 running issues

[Buccaneer]

 

A Martin 45 powerhead and lower unit, with a 40 gas tank and cowlings.
New engine gasket set, seals, poppet valve o-rings, etc. Compression is 95 & 90 psi
after putting it all back together, but it’s having “issues”.

After a change in throttle position, it often dies, and is hard to restart.
I tried a Tillotson carb from the Martin 40, and the Carter N carb that was on the 45,
with similar results in performance.
Plenty of fuel supply to the carbs, great spark.
Gas cap vent is not the issue.

Perhaps a vacuum leak in the crankcase?
Any other ideas?

VIDEO

https://youtu.be/bza_822Fs4c

Prepare to be boarded!

[necks]

Buc, Did you ever check the exhaust ports for being plugged up, or carboned up, from different fuel mixture oils, that could have been used in motor, before you got it?. Back in the day, when I was servicing outdoor equip, Lawn Boy was having issues on the D style motors. Mowers would start hard and run like your outboard motor does. Lot of people would mix car engine oil with the fuel. Mower would run fine until the exhaust ports would plug up with carbon, from using different brands of oil. The exhaust ports on the D series engine weren’t very large, so it wouldn’t take much to plug them up, big improvement when people started using 2 cycle oil with proper mixture. If my memory is correct there were three exhaust holes in block, when there was only one hole plugged up with carbon that mower never had any power or speed, let alone start, a real pain, in the arm, when they don’t start, especially when you went thru it and everything was correct.

Another problem that I encountered with those mowers, was the carb jet sizes. I repaired a mower that come from the state of Washington, ran fine their, had trouble starting in Mn, changed jet size in carb, started and ran fine. There’s another problem with engines, that drove me nuts, until fuel injection came in.

The only other thing I’ve tried, when I worked, hook up your spark testers, and whatever, start motor, turn lights completely off, and see if you can see anything arching out to frame, or losing spark, I tried that on cars in the dark when I had a miss in the engine, didn’t work all the time, but it did work. Those are some of the experience’s I had.

Gene.

[Buccaneer]

Gene, the powerhead was “gummy” with carbon, but the lower unit was
all torn apart, and cleaned for inspection and paint, so I gotta think
I cleaned the exhaust thoroughly, but anything is possible! Thanks.

Prepare to be boarded!

[The Boat House]

Watching your video it looks to be running out of gas.
As it will run for a while it would seem that the carb
bowl fills up but the supply of fuel is restricted and
cant keep up so the motor stops when the bowl is empty.
What I would suspect from watching your video.
If you let the motor sit for like 10 minuets and it will
start and run again for awhile, that would indicate that is
what is happening.
Tubs
.

[necks]

Buc, Engine looks pretty clean, that gummy caked on block looks like oil that came out of exhaust ports. Those pistons look like new yet, can’t have much run time on engine, with good compression that it has, sounds like Tubs may be on-to something. When I was learning about engines at local Vo-Tech, they always pushed about exhaust ports being plugged, from using different types of oil. The rule was Compression, Spark, Fuel, Exhaust Ports & muffler on 2 cycle engines. Do you have an Ultrasonic Cleaner with Heater, for cleaning carbs?. I bought one for the garage 2 years ago to use on small engine carbs, and couldn’t believe the crap and particles that come out of carb. I know that I must have condemned some good carbs that were just dirty or plugged. It’s a good tool to have in the shop, kinda like having a Merc-o-Tronic to test ignitions. To have the correct tools at your side to help you diagnose certain problems. Just think how much time you would have to purchase a new professional test tank, with hydraulic lift, with exhaust port, test wheels, and being able to run those outboards at full throttle, and no more backaches.

Gene.

[Buccaneer]

I checked a few things out yesterday, but the power went out
during the storm, and even with the big door open during
the day, I had to use my little flashlight to do much of anything.
I confirmed great fuel flow to the carb bowl
Compression 90 and 99 psi……… not sure if that’s good for a Martin 45 or not?
Pulled the flywheel for anything abby normal……. looked great, and
nice blue spark at both plugs.
No sign of water droplets on the plugs or in the cylinders after running it for twenty seconds
(started on third pull, died and would not restart)
Readjusted the carb to mag sync slightly.
Installed shorter spark plugs, as the top J-8’s terminal comes 1/4″ away from ground.

Didn’t get to retest yesterday….. rain, rain, blowing hard.
P.S. – this website is giving me fits, trying to decide if I’m really logged in!

Prepare to be boarded!

[necks]

Buc, Sounds like everybody was having problems the last couple of days trying to log-in, seems like it is working now. What gaskets did you replace if any, head gasket?, possibly leaking between cylinders, although 5psi difference is nothing. 9olbs should be plenty to fire that motor up. Next question, are you sure you are not loosing spark on either spark plug when motor decides to shut off, you need the boss out there to watch those spark testers when the motor is shutting down on it’s own, at least you’ll be able to check off ignition on the list. Carbs are another deal all there own. I had a couple different 4&6hp Johnsons, 70’s models, which the carbs were not very friendly, was the air-fuel mixture screw tip was worn off, from someone screwing mixture screw in to tight. Another problem was not using correct packing gaskets that hold needles snug, were leaking, couldn’t adjust carb. Does that motor have reed valves in it, if so one of those may not be sealing. I’m sure you have seen the old Tecumseh carbs, along with Walbro, chain saw carbs, it only takes one of those metering holes to be plugged up, and you have a carb that will drive you nuts, even with new carb kits. That’s where the Ultrasonic tool comes in handy.

[The Boat House]

I know you have changed the O rings but that
would be the next thing I would think to check.
Looking to be sure there is good contact so
there isn’t a leak. Wouldn’t be much of one as it
will run.
Did you get replacement O rings from Russ or are
you using something else.
Tubs
.

[Buccaneer]

Tubs, I pulled the carb again yesterday, confirmed that this Carter
Model N, N752 is correct for this motor.
Also pulled the poppet valve cover back off , pulled out the poppets,
and inspected the new o-rings from Russ. Looked good to me, and appear
to seat good.
After putting it back together, it was running better, but still having
issues with speed changes. If I left the speed steady, it seemed like
it would run forever.
I ran it for about 40 minutes total, and it died a few times during
speed changes, but I always managed to get it restarted, usually
after chocking it a little.
It has new crank seals, but I wished I would have checked the top
seal for leaks the last time I had the motor half way apart.

VIDEO…….
https://youtu.be/vbfglRrRI04

Prepare to be boarded!

[Buccaneer]

necks wrote:

Buc, Sounds like everybody was having problems the last couple of days trying to log-in, seems like it is working now. What gaskets did you replace if any, head gasket?, possibly leaking between cylinders, although 5psi difference is nothing. 9olbs should be plenty to fire that motor up. Next question, are you sure you are not loosing spark on either spark plug when motor decides to shut off, you need the boss out there to watch those spark testers when the motor is shutting down on it’s own, at least you’ll be able to check off ignition on the list. Carbs are another deal all there own. I had a couple different 4&6hp Johnsons, 70’s models, which the carbs were not very friendly, was the air-fuel mixture screw tip was worn off, from someone screwing mixture screw in to tight. Another problem was not using correct packing gaskets that hold needles snug, were leaking, couldn’t adjust carb. Does that motor have reed valves in it, if so one of those may not be sealing. I’m sure you have seen the old Tecumseh carbs, along with Walbro, chain saw carbs, it only takes one of those metering holes to be plugged up, and you have a carb that will drive you nuts, even with new carb kits. That’s where the Ultrasonic tool comes in handy.

Needle packing tight on HS needle, none used on low speed air adjustment.
New gasket set, including crank seals.
No water droplets found on plugs or observed in cylinders.
I shorted out one plug wire at at time, and motor stalled each time, so
yes, it seems to be firing fine, and plugs were a tan color.
This one is a poppet valve carb, with new o-rings.
I’m getting sick of looking at it, lol

Prepare to be boarded!

[Author]

Posts