Mariner (Yamaha) 4 HP outboard Starting Problems

[Arida]

Hi,

I have a 4HP 1980s vintage Mariner outboard (Yam built, 6E0 engine, earlier shear pin drive prop) which is used on a tender to get out to our mooring.

Once running, the engine is fine. However it is a pig to start, bad enough when cold but seemingly even worse if it was already used a couple of hours before. No signs of life at all when the cord is pulled repeatedly, then sudden firing after 10 or more attempts.

Any ideas what might be up? Would probably benefit from a general service, but am interested in any specific problems which are likely to affect starting. Or is there a particular technique which works well with these engines?

Engine is stored upright at home, but on its side in the car on the way down to the boat. It is stopped using the stop button as we approach the shore - I know letting it run out of fuel is generally preferred, but this is difficult to judge.

Any thoughts appreciated. Also if anyone knows a souce of a cheap propeller for this engine please let me know!

Regards, Rob

 

[noelex]

The most common problem with engines is blocked fuel jets. Mine clogs about every 6 months, but the carburettor can be removed and cleaned in about 1/2 hr.
However this usually causes the engine to start OK, but die as soon as it put in gear.

For your symptoms the first thing I would check is the stop switch these also fail often.

If it doesn't start try pushing the stop switch in and out a few times to clean the contacts then pull the stop switch out. This provides more pressure on the contacts than the red plastic tab, and it will start if this is the problem.

 

[rob2]

You already know there is not enough info to diagnose the problem, but that's half the problem! I just wanted to voice a nagging thought - I recall many years ago a coil failure on my Mini, I knew it was not right but apart from taking a few seconds to catch on the starter there were no other signs until it failed completely. I'd still suggest thorougly cleaning the carb as a first step!

We used one of these engines for a couple of years on a tender and really liked it but switched to a lighter engine as we didn't need all the power (or weight). It was one of the sweetest running and smoothest outboards I've known and worth sorting out.

Rob.

 

[Arida]

Thanks

Thanks both.

I certainly should clean the carb, but had tended not to think this was the problem for the reason suggested by nolex - eveything seems fine once the damm thing actually starts.

I will check the stop switch - this is actually an old-fashioned robberised push button rather than a modern switch which will take a kill cord, so given its use in a tender I should probably replace anyway.

Just struck me that I don't know the state of the spark plug either....

Regards,

Rob

 

[Lakesailor]

From what you say it may be that there is a failed oil seal on the main bearings.
This allows a pressure leak from the crankcase which is the scavenge chamber for the input fuel charge. A few pulls will charge the crankcase with enough fuel/oil mix to seal the bearings seals and the engine will start normally.
It's pretty common on chain saw motors.

 

[RobbieW]

I have one of those from about that vintage. It nearly always needs the choke for one pull, even when hot, then starts one/two pulls later.

 

[Arida]

Just to clarify...

I have one of those from about that vintage. It nearly always needs the choke for one pull, even when hot, then starts one/two pulls later.

RobbieW

Are you saying that you turn the choke fully clockwise for the first pull and then fully anticlockwise for subsequent pulls?

Reagrds,

Rob

 

[VicS]

The problem could be one of numerous things.

Check that you have good strong blue spark. CD ignition I believe so should jump a good 3/8 inch

Always worth trying a new plug if you have not already done so.

Suddenly starting after a number of failed attempts would make me check the stop button .. but if you have a good spark from the outset that's not the problem.

If you have good plug and a good healthy spark try spraying some fuel mix into the carb throat. If it responds to that then it's likely to be a fuel problem or a dirty carb, but if once started it runs well and idles properly a dirty carb is not a likely cause.

It could be bad crankshaft seals as LS suggests. I guess it's a problem he has experienced but I don't think it is a common one.

You have to experiment with throttle and choke settings to find what works best for your engine. If the carb is set a bit lean it'll likely need more choke. If it's a bit rich then probably rather less. Some will start with little throttle some need practically full throttle ( if that's possible)

 

[RobbieW]

Are you saying that you turn the choke fully clockwise for the first pull and then fully anticlockwise for subsequent pulls?

Exactly so, we're currently in the Balearics (30+) and only about twice has the engine started without choke. It also really doesnt like old fuel! As Vics suggests you probably need to experiment with choke and throttle settings.

 

[Arida]

Thanks

Exactly so & it really doesnt like old fuel!

Thanks for the clarification, i will try it just like that. Ran on fuel from last season when I first started this year, but has been refuelled with fresh stuff a month or so ago.

Vics, I have taken your advice and ordered a new spark plug.

Rob

 

[noelex]

Full choke on mine as well even first start in hot weather.
If its been running in the last 10 mins and it's hot is only time you can get away without the choke (on mine anyway). As soon as it fires the choke needs to put away.
Generally needs a bit more throttle to start as well compared other outboards I have owned.

 

[Arida]

Oily plug & too deep?

Sorry to reopen this thread, but:

Replaced the plug today. Old one was quite oily - if it was a car I know what I'd think, but perhaps par for the course for an elderly 2 stroke outboard? Do others find periodic cleaning necessary?

Also, I'm wondering whether my starting problems might be exacerbated by the outboard leg being a bit deep in the water - exhaust pressure and all that? I believe it is the standard shaft verion, but the design of the tender means that the engine body sits quite close to the water and the cavitation plate must be 9" under. Is that likely to be an issue? I will probably be looking to modify the transom pad to change this anyway, as the channel out to my mooring can become very shallow so it is not exactly hepful anyway.

Regards,

Rob

 

[ex-Gladys]

Thanks for the clarification, i will try it just like that. Ran on fuel from last season when I first started this year, but has been refuelled with fresh stuff a month or so ago.

Vics, I have taken your advice and ordered a new spark plug.

Rob

These days petrol deteriorates very quickly. I had 12 month old petrol on my Tohatsu 3.5, and drained it out, since it smelt like old paint rather than petrol, don't be afraid to top up a petrol car with the contents of your can and replace....