1994 Yamaha 70HP runs great until you put it in gear

[johnny whaler]

I have a 1994 Yamaha 70 2 stroke I just bought on a 15' whaler. The guy I got it from was a straight shooter and told me he had it out yesterday and the boat ran great. He offered a sea trial and we just started it in his driveway with the muffs. It ran great.

I took it to the ramp today and it runs great until you put it in gear. It has no power! I ran a compression test and the 2 top cyls were dead even at 140 and the bottom was 130. (my tester is off a little - I doubt it's this high). I have great spark. I even pulled the plug wires off 2 at a time and it will run on one of the 3 cyls. It actually ran on each one all alone.

The control box is shot and there is a red lever inside betwen the carbs and the oil tank you need to flip up manually to start it. I guess it's the choke? But there is no choke flap on any of the carbs? I turned the lever all the way around and it fired up instantly. It will idle all day long and you can rev it up with the warm up lever but when you put it in gear it's a dog and then dies. It will start right back up again.

I am led to believe there is something shot in the control box. He did tell me it was repaired a few times and it could use a new one. The choke button does not work.

Any ideas? I have great spark, compression, seems to be getting fuel? Any help is appreciated.

 

[Ray Neudecker]

Re: 1994 Yamaha 70HP runs great until you put it in gear

Every thing says you aren't getting fuel. You need to get the manual and get the primer system straightened out. If the primer is left on it will cause the motor to flood out. A fuel restriction will also cause the same symptoms.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

That's how it's acting. It will run and it will rev way out in N but once in gear forget it!

This choke system is greek to me. I never saw one like it. How does it work? what does the red lever do?

 

[rodbolt]

Re: 1994 Yamaha 70HP runs great until you put it in gear

its a fuel primer system.
its called prime start, it has no choke functions on the control box.
its either automatic or its broke.
your describing a fuel restriction.
so far the compression numbers look acceptable, fix the fuel system.
with that system you also do NOT use the warmup lever when starting.
the red lever is a manual enrichment overide.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

There is a choke button on my control box?

There is a water separator filter on the transom and the usual fuel filter.

Would a 70 mile ride down bumpy roads jar something in the water filter? Just seems strange that it ran great less than 48 hours ago?

I was pretty amazed it ran alone on each of the 3 cyls.

Thanks for the help. I guess the next stem is to pull the outlet off the fuel pump side to se if fuel is coming out?

 

[rodbolt]

Re: 1994 Yamaha 70HP runs great until you put it in gear

ALL 703 boxes had the push to choke or choke switch. NOT ALL yamaha engines have a choke.
yours happens NOT to have a choke, all your going by is word it worked. maybe maybe not, NEVER NEVER buy a used rig without a thourough seatrial,preferably with someone who at least stayed in a holiday inn.
why would you unplug the fuel line ?
isnt that kinda assinine? think about it.
what does the fuel pump actually do?
can you bypass the pump function?
usually a bad pump will make it run very rich or it will take off for 50 ft and fall on its face when the fuel bowls run dry.
now tell me how we can use the fuel primer bulb to test both function.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

I got the boat cheap and my buddy knows the guy. He's loaded and could care less if he threw the boat away. I would bet dollars to doughnuts it did run good the other day.

I started it with the red lever. After reading some stuff here I see just pump the ball and turn the key.

The water is 50 degrees here. My old evinrude starts and goes, do these engines need more warm up time? I warmed it up or close to 10 minutes.

I had it running and tried to sqeeze the bulb when I put it in gear and it didn't help it rev up. I am not to clear on this "non-choke" stuff. This is advanced for me. I hate to bring it to he dealer but I may be in over my head.

So I guess you are tellign me the control box has nothing to do with it and the fuel pump is good more than likely. I have good compresion, good spark. If the fuel pump outlet isn't where you would check fuel flow what's next? the carb bowl screws?

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

I should add. This motor will not start without pushing the red lever up. I tried the proper starting procedure several times and it won't start. Once I flick the red lever it will start and unless i sht it off quickly it will die.

 

[JUSTINTIME]

Re: 1994 Yamaha 70HP runs great until you put it in gear

the read lever is call fuel enrichiner/cold start/prime start

u can flip it, all it does is enriches the fuel

like rodbolt says it works or does not work

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

So where is the next place to look? Like I said, the old style engines with a choke butterfly are pretty simple. I still have no idea how this prime system works?

 

[rodbolt]

Re: 1994 Yamaha 70HP runs great until you put it in gear

like its been said, to test the system you will need a service manual and a multi meter.
the prime start on that engine is fairly simple. it uses a wax pellet in a heater to move a rod. as the rod extends it leans out the mix as it retracts it allows a small pump to enrich the mix. a balance tube insures all 3 cylinders do the same.
the assy is mounted on the port side of the middle carb.
there are rod length specs and visual tests as well as voltage tests to make.
if spark is good and compression is good and the advance rod on the side is attached 99% chance you have carb issues.
the fuel line primer bulb is just that. it simply primes the system. its a manual fuel pump.
a quick check is to have someone load the motor while you spray premixed fuel down each carb throat with the hull securly tied down.
sometimes all it takes is to manually block or partially block the air horn opening to each carb one at a time and force that cylinder rich.
I like to spray them myself.
with the engine off will the fuel line primer bulb pump up firm ?
also best memory serves me if your not careful you can actually shut off the prime start with the red flag.
it should have 3 locations,auto,maual and off.
you can also try to drain each bowl into a clean paper towl and see what comes out.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

Thanks for the info. I did notice when I pulled the airbox of and put my hand in front of the lower carb to restrict some of the air it seemed to run a little stronger. Once again showing a possible fuel restriction.

The ball pumps up roch hard. I'll be messing with it later today. I have acess to a boat ramp and can keep it on the trailer with the engine in the water to test it.

Thanks for the help. I ordered a book today online.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

I ordered a Seloc manual. Is this a good manual? I have had the Clymer's in the past and they seem to general.

Anyone's opinion on this would be respected and appreciated.

Once again, thanks for pointing me in the right direction.

 

[mat4]

Re: 1994 Yamaha 70HP runs great until you put it in gear

I ordered a Seloc manual. Is this a good manual? I have had the Clymer's in the past and they seem to general.

Anyone's opinion on this would be respected and appreciated.

Once again, thanks for pointing me in the right direction.

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

I found something out today. The gas tank that came with the boat had the vent screw mising. It rained hard here on Thursday. The boat was used Wednesday and ran great. I have a feeling that water got into the tank. I asked the guy I got it rom and he left the tank on the boat thursday. there is a water separator on the boat. I will replace the filter.

 

[floppo]

Re: 1994 Yamaha 70HP runs great until you put it in gear

Johnny, listen to these folks who have responded to your request. What they say is from experiance. Basically they are telling you that there is no choke function on this motor. When you put the key in and turn it to on the prime start is operating. At this point do not raise the lever to increase RPM. Just turn the key to start, count to 5 and release if no start. Continue to do this until it starts. Make sure the primer bulb is still hard and full of fuel. If it is idleing fine, no surging or does not die get the carbs checked. Good idea to purchase a yamaha manual. Lots more info than aftermarket.

 

[v12mac]

Re: 1994 Yamaha 70HP runs great until you put it in gear

15 Whaler with a 70hp, Great rig! Lots of fun, keep it fun by taking it to a good mechanic this time around at least. Spend a few bucks on profesioal trubble shooting.
Get fimalar with the motor slowly once you know it is running 100%.

Mac

 

[johnny whaler]

Re: 1994 Yamaha 70HP runs great until you put it in gear

it's there now. The wiring harness is all messed up. I am having a new harness put in:^

 

[v12mac]

Re: 1994 Yamaha 70HP runs great until you put it in gear

Cool, Let us know how it goes!
Mac