Yamaha 5 hp 2 cycle problem

[roberttigar]

My trusty tender engine has worked well for a long time. I have let it sit unused for the last 8 months and now it wont start. It wiill fire on starter fluid, so I assume the electrical system is ok.
That leaves the fuel system, which I have systematically worked thru using the shop manual.
The manual states that the least like problem is the carb-more likely the flow of fuel. So I checked the fuel lines and all seems to be ok. The fuel is ethanol free and I got a good flow from tank to carb.
Which leaves me with the fuel pump . Its mounted to the side of the carb and since its last and 20+ years old it may be the cause of my problem.

But it seems you dont buy a replacement pump for these small engines, you buy the parts -about 10 items and assemble them to replace the existing pump.

Has anyone done that? assembled the replacement pump? What kind of problerms did you run into?

Bob

[Sailmonkey]

A manual that states the least likely problem is the carb is dead wrong in my humble opinion.

After sitting 8 months, pull the carb off, remove the float bowl and pull and clean the float, float pivot, and float needle. These are all likely stuck with dried fuel gunk. I’ve gotten to the point with our 5hp 2stroke mariner where I can do this in 10 minutes if I put my mind to it.

[Bill O]

Originally Posted by Sailmonkey

A manual that states the least likely problem is the carb is dead wrong in my humble opinion.

After sitting 8 months, pull the carb off, remove the float bowl and pull and clean the float, float pivot, and float needle. These are all likely stuck with dried fuel gunk. I’ve gotten to the point with our 5hp 2stroke mariner where I can do this in 10 minutes if I put my mind to it.

100% agree that it's most likely a carb issue, especially if you didn't run it dry and left fuel in the bowl. The only additional item I would add to the list above to would be to clean the main jet while you have it apart.

[jamhass]

Unless the engine was well-drained, it's likely gunked up the carb. Yes, they can be cleaned, but usually with significant effort and less than satisfying results. Often the carbs on smaller engines are so inexpensive that cleaning doesn't make a lot of sense, especially given the price of good carb cleaners.

I recently spent several hours on an older 2-stroke carb to no avail. Amazon sent me a new carb for less than 20 bucks and the damn think now runs like a champ, starting on the first pull.

[MicHughV]

As above, a two stroke engine has oil mixed in with gas. If this stays in the engine for any length of time, the fuel will evaporate, leaving the oils behind.
Those carbs have tiny filters, about the size of a matchhead...these get clogged very easily.
You have two options, a) remove the carb and clean it, or get it cleaned...or b) order a new carb online, they are not very expensive. keep the old on as a spare.
My advice, based on many years of experience with these little engines....get a new carb.
Finally, be sure to run non-ethanol fuel thru' the engine. Yes, it can be a pain in the arse to get sometimes, but most marina's sell it. Regular pump gas has 10% ethanol added, this will eat anything plastic, which will eventually get into the carb.

[Mike Burch]

Petrol goes stale, and as others have said above, the oil in two-stroke mix adds to the problems. Make yourself a fresh brew, and avoid the stuff with added alcohol.

I always run the carb dry when finishing a job with any two-stroke engine, afloat or ashore. I just turn the fuel off and let the thing run until it coughs and dies.

[Sailmonkey]

Originally Posted by jamhass

I recently spent several hours on an older 2-stroke carb to no avail. Amazon sent me a new carb for less than 20 bucks and the damn think now runs like a champ, starting on the first pull.

$20 bucks?!?’

I just looked up the carb for my OB. The original is $322 and the Amazon knockoff is $78.

[jamhass]

Guess I'm glad my old 2-stroke was a Johnson ...

[MicHughV]

I've had issue with carbs before. I took 'em off, cleaned them as diligently as I could, put them back, but still no start.
Out of frustration, I took the dismantled carb to a local outboard shop, where for a small fee, about $20, they soaked it in some or other concoction they have there in a large drum, over night.
Come back the next day, picked up my pieces, re-assembled the carb...voila....ran like new.
I don't know what they have in that drum, but whatever it is, it cleans carbs.

[sailhand]

Have been using these 4/5 yamaha/mariners for decades and 98% of the time its fuel and rubbish in carb and 2% kill switch in my experience. Be careful when removing jets and nozzle in particular. Use the right size screwdriver with a tight fitting blade. When replacing the nozzle above the jet do not tighten too much, just barely nip it home. The jet sitting underneath holds it in place. In Australia we have a two part glue system for pvc plumbing pipe. The primer fluid from this two part system is the same as many of the carby cleaner fluids and sprays available in Australia. You must remove the fuel pump before soaking as it is rubber and does not react well. Remove all components and place in primer fluid. Leave for several hours and then remove and clean with compressed air. Our local plumbing suppliers have this primer fluid in 10 litre tubs in both clear and pink dyed variety really cheap.