Mariner 75hp lost power - fuel problem?

tristenhill · 14 July 2005, 09:34

Hi,
Wondered if anyone could help. I've just brought a boat with a 2 stroke Mariner 75hp (4 cylinders) believed to be mid to late 80's, no oil injection. Took it out for the first time last night.
When i got in the water it would start but when i then put it into reverse the engine would dye. Eventually got going so could have just been a cold engine. However after running at near full throttle for 10 mins slowed down and was just chugging very slowly when the engine died. Wouldn't start again fo a long time. Eventually fired up, gave it some throttle, we started going then we lost power and the thing just stopped and wouldn't start again. I don't know much about outboards as it is my first boat but seems that maybe it could be a fuel problem - not getting through?. One thing i did notice is that when pumping the primer bulb, i believe it should get hard when full with fuel, but it doesn't seem to ever get hard - after a good few pumps it is just as soft as when i started. The only other thing is that i filled my fuel tank with 25 litres of fuel then went to add the oil but couldn't quite put 0.5 litres of oil in to give a 50:1 ratio as the tank was overflowing. Therefore the mixture might have been a bit lean, was going to add more oil when we had burnt a bit of fuel but didn't get the chance. Don't know if this could cause a problem.

Hope someone can help.

Tristen Hill

swginn · 14 July 2005, 15:05

Sounds like a similar problem I had with a Mercury 75, albeit the 3 cyl 2000 model. She was down on power (only firing 2 cylinders) and would cut out going into reverse. Turned out to be a fueling problem.

The fuel hose was too narrow and the priming bulb was fitted the wrong way around. When priming also, there is an arrow on the bulb. This should be pointed upwards when you squeeze the bulb. These seem like simple things, but they could save you having to get it looked at by your dealer.

HTH!!

Biggles · 14 July 2005, 15:08

You might be better off posting this on www.iboats.com but for whats it worth can you tell me if when you keep pumping the pump fuel starts to spill out of the throat of the carbs. If so its time for a carb rebuild. Even so you should still get it going eventually.

Regards Nick R.

Turbodiesel · 15 July 2005, 21:05

You could also have a split pump diaphragm, if your pumping and you cant see any fuel, you could just be filling the crank case full of fuel. Although you would probably smell it. (the fuel that is)

Hightower · 16 July 2005, 00:26

Where abouts do you launch from Tristen?

Tim M · 16 July 2005, 20:58

I had a similar problem; engine died at low speeds and when changing from Forward into reverse and visa-versa. Turned out to be a blocked idle jet in the carb.
Also, with regard to your priming bulb; try pumping for longer in order to get it hard. Sometimes it takes a good few minutes pumping to get mine hard (and that's over a 3m fuel pipe run)

tristenhill · 18 July 2005, 13:54

Quote:

Originally Posted by Hightower

Where abouts do you launch from Tristen?

i usually launch from lee-on-solent

tristenhill · 18 July 2005, 14:01

Hi guys, cheers for all your help - realised the next day when checking the boat over the vent in the fuel can was closed - this must have been why i had the problems - or so i thought.

Opened the vent and took it out friday and all seemed fine. Also upped the idle a little as engine seemed to die when in gear at low revs.
When going into reverse it seemed to die but i realised that if i went into reverse to the fist "click", without giving it any more revs - left it there for a second then went for a bit more speed it wouldn't stall. think i was adding the gas a bit quick!

however, when i took it out on saturday - everything seemed fine initially then had to give it more revs when starting (above fast idle). when i then go back to neutral to then put it into gear the engine dies again!!!

thanks again

Hightower · 18 July 2005, 18:34

Isn't it a bit busy with all those jet skiers?

Your profile says you run a Shakespeare, is that RIB or Hard boat?

tristenhill · 19 July 2005, 14:26

i don't launch from the slipway where the hvoercraft is as there are loads of jetskiers there - but launch from the one on the corner near the sailing club - its not so bad there.

where do you launch?

my shakespeare is a hard boat - so probably on the wrong site really!!!!