70 HP yamaha no power under load

[dashmore]

Please help I have a 70 HP Yamaha,1986 model#70ETLH it ran fine 2weeks ago but last time out it did not have enough power to pull boat off trailer.
I took it home changed plugs put on the muffs and it worked fine.Took it to the water and still no power. There is a toggle switch on the control unit that works like a choke it can hit it and motor will power up an go but only about 1/2to 3/4 speed and it still has no power to pull back onto trailer. I also checked fuel filter and cleaned it .Any guesses of what to do before taking it to shop Pros? Thanks in advance for any response.

 

[BruceAML]

Re: 70 HP yamaha no power under load

Your motor is a 1987 model and not a 1986 model. What spark plugs did you use? What is the gap and did you torque them in? It sounds like a fuel pump problem. The pump is very easy to install. What fuel filter did you use?

 

[dashmore]

Re: 70 HP yamaha no power under load

I pulled old pulgs and got same I dont know name brand,I used old plugs gap to set new I think it was .32 I do not have a book on this motor yet. but i will.The motor is runnig just like before new plugs,I took the clear glass bowl offwhere fuel comes in drained and cleaned it and again it runs fine out of the water but i want to use it in the water.I think i found fuel pump if it is blackbox with fuel line coming and out can I take it off and clean it or should i replace it.will it hurt the motor to try and run it until I get it figured out.

 

[BruceAML]

Re: 70 HP yamaha no power under load

At the very least you need to order a Yamaha owner's manual from Yamaha. The part number is LIT-18626-00-52. You need to be more careful when installing spark plugs. The correct spark plug is an NGK B-8HS10. The gap is .035-.039". Metric gap is 0.9 - 1.0 mm. The correct spark plug torque is 14 ft lb. If you do not have a torque wrench, try and find a friend who has one. Here is a link to order your manual:
http://www.yamahapubs.com/html/itemsearch.jsp?type=OB&Year=1987&Brand=&model=70ETLH
I would also get a few containers of Yamaha Ring-Free and add that to the gas in the amount that is on the back of the container. You can not clean the fuel pump, replace it completely. The part number for the fuel pump is 692-24410-00-00. You also need to order the fuel pump mounting gasket, 650-24431-A0-00.

 

[Yamajoe]

Re: 70 HP yamaha no power under load

Check for restrictions or airleaks in your fuel system, your carbs may need a clean, to check if you have fuel pump problems have some one squeeze the primer when the motor is trying to power up up, if this works then your fuel pump is suspect.

 

[john156]

Re: 70 HP yamaha no power under load

Please help I have a 70 HP Yamaha,1986 model#70ETLH it ran fine 2weeks ago but last time out it did not have enough power to pull boat off trailer.
I took it home changed plugs put on the muffs and it worked fine.Took it to the water and still no power. There is a toggle switch on the control unit that works like a choke it can hit it and motor will power up an go but only about 1/2to 3/4 speed and it still has no power to pull back onto trailer. I also checked fuel filter and cleaned it .Any guesses of what to do before taking it to shop Pros? Thanks in advance for any response.

We just had a similar problem We isoalted which cylinder was the problem by running the engine in idle and removing the plug leads on at a time (use insulated pliers) if engine change with plug lead removal then cylinder is working, if no change then problem with that cylinder. Now rotate plugs, if problem now with different cylinder then it is aplug or electrical problem, if with same cylider the probably a fuel problem. Check carburetta for that cylinder. Ours was a sticking float needle.

 

[dashmore]

Re: 70 HP yamaha no power under load

FYI took it to the shop had the carbs cleaned and adjusted now it cranks on idles great and will run like a new one. Thanks for your input gave me an idea what to expect going into the shop.
Thanks Again