Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 16-11-2021, 05:28   #1
Registered User

Join Date: Oct 2008
Posts: 322
Yamaha 5 hp 2 cycle problem

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
roberttigar is offline   Reply With Quote
Old 16-11-2021, 05:44   #2
Registered User
 
Sailmonkey's Avatar

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 9,280
Re: Yamaha 5 hp 2 cycle problem

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. Iíve gotten to the point with our 5hp 2stroke mariner where I can do this in 10 minutes if I put my mind to it.
Sailmonkey is online now   Reply With Quote
Old 16-11-2021, 06:22   #3
Registered User
 
Bill O's Avatar

Join Date: Jul 2015
Boat: Bruce Bingham Christina 49
Posts: 2,655
Re: Yamaha 5 hp 2 cycle problem

Quote:
Originally Posted by Sailmonkey View Post
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.
__________________
Bill O.
KB3YMH
https://phoenixketch.blogspot.com/
Bill O is online now   Reply With Quote
Old 23-11-2021, 18:28   #4
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat Sold)
Boat: Former owner of a Valiant V40
Posts: 991
Re: Yamaha 5 hp 2 cycle problem

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.
jamhass is offline   Reply With Quote
Old 23-11-2021, 18:58   #5
Marine Service Provider

Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 4,111
Re: Yamaha 5 hp 2 cycle problem

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.
MicHughV is offline   Reply With Quote
Old 23-11-2021, 19:25   #6
Registered User

Join Date: Oct 2020
Location: New Zealand
Posts: 50
Re: Yamaha 5 hp 2 cycle problem

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.
Mike Burch is offline   Reply With Quote
Old 25-11-2021, 18:30   #7
Registered User
 
Sailmonkey's Avatar

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 9,280
Re: Yamaha 5 hp 2 cycle problem

Quote:
Originally Posted by jamhass View Post

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?!?í

I just looked up the carb for my OB. The original is $322 and the Amazon knockoff is $78.
Sailmonkey is online now   Reply With Quote
Old 01-12-2021, 18:19   #8
Registered User

Join Date: Jan 2008
Location: SF Bay Area (Boat Sold)
Boat: Former owner of a Valiant V40
Posts: 991
Re: Yamaha 5 hp 2 cycle problem

Guess I'm glad my old 2-stroke was a Johnson ...
jamhass is offline   Reply With Quote
Old 01-12-2021, 18:47   #9
Marine Service Provider

Join Date: Jan 2019
Boat: Beneteau 432, C&C Landfall 42, Roberts Offshore 38
Posts: 4,111
Re: Yamaha 5 hp 2 cycle problem

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.
MicHughV is offline   Reply With Quote
Old 02-01-2022, 18:50   #10
Marine Service Provider

Join Date: Feb 2017
Posts: 65
Re: Yamaha 5 hp 2 cycle problem

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.
sailhand is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
yahama 15hp 2 cycle cooling water problem sailalibi Auxiliary Equipment & Dinghy 2 24-07-2019 08:19
Yamaha 8 hp vs Yamaha Enduro 8 hp bsobo Auxiliary Equipment & Dinghy 0 27-11-2011 10:22
Carb Problems - '97 Yamaha 15hp Two Cycle amytom Engines and Propulsion Systems 13 02-04-2011 18:53
Yamaha 5hp Outboard Problem landonshaw Auxiliary Equipment & Dinghy 6 05-01-2010 12:44

Advertise Here


All times are GMT -7. The time now is 10:38.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.