Mariner/yamaha 8b 1982

[Lubosleftboot]

Hi Guys

Recently acquired a mariner 8 hp 2 cyl 2 cycle engine of around 1982 vintage that is virtually identical to the yamaha 8b engine of the same vintage and I have an irksome problem.

This engine will start and run for about 30 secs then it dies and refuses to start. I have checked the points and timing and they are ok in that there is a nice fat spark white in colour so I know that the charging coil is working. I have also cleaned all the wire connections and earthing points for the coils and isolated the kill switch so I am pretty sure its not the ignition system thats the culprit but I am more than willing to listen to any suggestions on the ignition system as there may be something I have overlooked.

I have also removed and cleaned the carburetor and there is fuel present in the bowl and the jets seemed clean to me in that after removal I could see clearly through the jets apertures. The fuel bulb primes as it should so I am at a loss as to why this motor will only run for 30 secs.

Compression is also excellent in both cylinders.

Can condensers cause this type of fault? Or is this a fueling problem? All suggestions are appreciated guys

LLB

Engine serial number 8M 677-370218

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Righty ho nada zilch the big goose egg aint going to get this motor working chappies...:facepalm:

Been at this motor again today have stripped the carb totally and cleaned it with carb cleaner including all jets and orifices in the carb body.

I have checked the fuel diaphragms and both of these are showing no sign of any damage...the primer bulb goes hard once it has fueled the engine as it should and does not loose pressure.

I connected a inline spark tester and proceeded to crank the engine. The tester is glowing as it should indicating that the spark voltage is being delivered to the plugs. As the motor still refused to start I noticed on here about spraying a petrol oil mix straight into the carb venturi. When I do this the engine will start for about 10-20 secs and then cut out again so leading my to believe this is a fuel problem.

What has me perplexed is that I know that fuel is getting from the fuel can via the primer bulb to the fuel filter on the side of the engine and then on to the carb fuel bowl. I know this as the bowl was full of fuel when I removed the carb for cleaning today.

So it looks to me as though for some reason unknown to me the fuel is not getting from the main jet to the engine. The reeds defo work as spraying fuel/oil mix straight into the throat of the carb gets the engine going for 20 secs or so.

When started the engine will respond to the throttle but then as I have said previous it just dies a death and will then refuse to start.

Is there some system of vacuum that pulls the fuel through the main jet on these motors that could be causing this problem?

For the mods attention this engine is just a rebadged yamaha 8B so this may be relevant to the yamaha forum as well.

Some help or suggestions would be very much appreciated guys.

LLB...

 

[carholme]

Re: Mariner/yamaha 8b 1982

Once it does start, can you keep it running by pumping the bulb?

Gerry

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Once it does start, can you keep it running by pumping the bulb?

Gerry

Hi Gerry

Thanks for your response buddy...It still cuts out even with me pumping the bulb mate.

LLB

 

[carholme]

Re: Mariner/yamaha 8b 1982

It almost sounds like a float adjustment or saturated float. Do you have a manual for the engine?

If not let me know and in the meantime, here is the carb adjustment for the Mariner 8A, which yours is:

http://web.ebscohost.com/serrc/pdf?...-b464-071fdd837dbc@sessionmgr14&vid=6&hid=108

Gerry

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

HI Gerry

Thanks once again for your help and the link and I dont have a manual for the engine unfortunately.

I dont think the float is saturated as I could not hear any liquid inside it when I shook it today but even though there is fuel present in the bowl maybe the float adjustment is out as you suggest...I will have a look at that tomorrow and report my findings in this thread.

LLB

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Hi Gerry

8a has a different carb to my motor bud..here are a couple of pics.

mariner 8M according to the serial number bud.

 

[robert graham]

Re: Mariner/yamaha 8b 1982

Sounds like it's taking about 30 seconds for the motor to suck the fuel out of the carb float chamber, but the carb float needle is sticking in the float valve and not letting fuel in. Remove/check/replace that float valve/needle. It may have a bad rubber seat or warn needle causing it to stick. When you have the float out check to be sure that needle is freely moving up and down. Good Luck!

 

[carholme]

Re: Mariner/yamaha 8b 1982

LLB;

Sorry about the 8A, yours is an 8B for parts purposes.

Here is the parts listing for your s/n:

http://www.crowleymarine.com/mercury-outboard/639.cfm

Check the second carb listed, I think that is yours.

Here is the link to the 8B carb maintenance:

http://web.ebscohost.com/serrc/pdf?...bf57-3fc38be64b89@sessionmgr115&vid=6&hid=126

I will prepare directions for you to get the full manual and post later.

Gerry

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

LLB;

Sorry about the 8A, yours is an 8B for parts purposes.

Here is the parts listing for your s/n:

http://www.crowleymarine.com/mercury-outboard/639.cfm

Check the second carb listed, I think that is yours.

Here is the link to the 8B carb maintenance:

http://web.ebscohost.com/serrc/pdf?...bf57-3fc38be64b89@sessionmgr115&vid=6&hid=126

I will prepare directions for you to get the full manual and post later.

Gerry

Gerry you are some man thanks ever so much for your time and help it is truly appreciated

LLB

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Sounds like it's taking about 30 seconds for the motor to suck the fuel out of the carb float chamber, but the carb float needle is sticking in the float valve and not letting fuel in. Remove/check/replace that float valve/needle. It may have a bad rubber seat or warn needle causing it to stick. When you have the float out check to be sure that needle is freely moving up and down. Good Luck!

Hi Robert

Thanks for the reply I will check that out tomorrow as well buddy

LLB

 

[carholme]

Re: Mariner/yamaha 8b 1982

LLB;

Go here for the manual:

http://search.ebscohost.com/

User ID is marshall

Passwrod is public

When you have logged in, select Small Engine Repair

Then, select Marine/Boat Motors

Then, select Mariner

Then, select OUTBOARD 2-220 HP, 1976-1989 (INCLUDES ELECTRIC MOTORS

Then select the sub categories as needed. Note that when selecting the sub categories, depending on the size of the file, you may have to wait 20/30 secs for the page to load.

You can then download the various sections to your computer as needed.

Gerry

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Once again thanks Gerry you have been a big help with this problem buddy

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Hi guys

Downloaded the manuals kindly put my way by Gerry but I still have not managed to get this motor to function correctly. The float height is as it should be and I have cleaned the carb 3 times now with carb cleaner.

My question is this is can the fuel pump diaphragm keep the fuel primer pump under pressure yet still not deliver fuel to the engine?

LLB

Another thought can the fuel pump be put together the wrong way round?

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Can anyone shed some light on this please..

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Up you go...would appreciate a bit of input fellas

 

[carholme]

Re: Mariner/yamaha 8b 1982

LLB;

Sorry for not having come back but have been blowing snow for the better part of the last two days. Just under two feet with ferocious winds.

Have you had the pump apart or has someone else been in there? You can always check to ensure that the check valves are installed correctly. When you pump up the primer bulb, does it hold pressure or does it seem to go soft fairly soon?

Gerry

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Hi Gerry

The bulb seems to hold pressure fine but when I squirt fuel/oil mix in to the carb venturi the engine starts and runs before cutting out again. It seems as tho the fuel gets to the carb but not from the carb and into the motor???

Once again thanks for your input Gerry its appreciated.

LLB

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Bought another complete carb today from ebay will check it out fit to motor and see if I can get this motor to function.

 

[Lubosleftboot]

Re: Mariner/yamaha 8b 1982

Righty ho still no further forward with this piece of c**p looks like it wants to got to the trash.

Fitted different carb but right one for this motor and it still does the running for 5-10 secs and then cuts out..I am totally at a loss as to why this sod wont function as it appears to me that the fuel is getting to the carb but not into the engine casings

Here is a pic of the plugs



The primer bulb has gone hard and keeps pressure on both the carbs I have fitted to this engine so why is the fuel not getting into the engine..can dead reed valves be the cause?

Need some help with this one guys or I am just going to bin the motor as its beyond me as to why it is acting in this manner.

LLB