Logo
FULL SITE MENU

Hard starting 1991 200hp

Keithm18

Keithm18

Regular Contributor
Hi All. I have a new to me 91 200hp v6, motor has just over 500 hours on it.

runs great and operates at 5000 rpm with with no problems. When warm starts no problem, a simple turn of the key, however when starting for the first time or from cold i have to crank the thing for close to two minutes to get it going and it stalls out often when cold.

here's what i have done:

compression good 115 across all cylinders, spark is great checked with spark gap checker, spark plugs are new surface gap type, correct according to manual. Fuel is fresh and new, fuel bulb replaced

my starting procedure is varied to what works. I start by pumping the fuel ball until hard then turning the ignition on and waiting for the beeps. Two or three quick ones i think. I then turn the key to run and push it in for a second or two and then crank the motor with the key pressed in. After about 10-20 seconds i release the key and repeat. After doing this three to five times i may try cranking without pushing the key after quite a bit of fiddling it starts. This includes a combination of pushing key in while cranking and not pushing it in and using the fast idle lever. Most of the time it won't start with the idle lever raised, but i use it quickly after starting to rev the motor to prevent it dying.

There's a lot of smoke just after the start and i get the impression i may be flooding the motor.

I have confirmed the fuel enricher is working by pumping the primer ball hard and pushing the key in. With the pipe going to the carbs removed i can see fuel exiting from the enricher.

the idle on this motor when warm is around 650 - 700 rpm in the water.

is my start procedure wrong or is there something i can adjust to solve this. Thanks
 
With the pipe going to the carbs removed i can see fuel exiting from the enricher.
Click to expand...
How much fuel is it producing in 5 seconds? Have you thoroughly cleaned/rebuilt the carbs?
 
Hi Guyjg. Thanks for the reply. I didn't think to measure it, but it kind of just dribbled.

I bought the boat from a Yamaha dealer who had taken it on a trade, they told me they had rebuilt the carbs and done a full service.. Took it out on the trailer yesterday for the roadworthy into my name and it was dripping fuel all over from the drive with the motor up. got it home removed the silencer and found when I pumped the ball fuel would dribble from the number 6 carb..... and when the throttle was wide open (Engine off) the middle carbs butterflies were only half open, as the screw to the Linkage was loose..... so loose linkage and wrong float level on number 6 carb...wonder what other gremlins are lurking.

Not sure what apprentice they had service the motor but it's going back for them to sort these things out.....I'm also asking them to look into the hard starting issue.

Can't believe a dealer wouldn't check their work....

As a matter of interest can you tell me what the correct number of outward turns on the idle screws on the carbs is?
 
You need to replace the check valve that pressurizers the oil tank. Around $15.00. If the oil tank stays pressurized after shut down it will over oil the engine and cause hard starts and lots of smoke once you get it started.
 
Thanks Chris and Guy.

Got it back to dealer and they got it back to me on Friday. Took it out on Saturday and hard start was a little better, but think this may be me getting used to motor. Bottom carb no longer leaking either. When idling around while people are settling onto tubes etc the thing would just die, hitting the choke or pumping the ball when it did this wouldn't help stop this and when you hit the enricher it just dies even quicker.

Started using fast idle lever to get it started without pushing key and then had to let it fast idle around 5-10 seconds before letting it settle to normal idle and going to wot, if you don't it dies straight after starting. WOT still flawless and when above idle this thing is a monster. Straight to 5000rpm.

A mate of mine with a merc said it sounds like the fuel pump isn't getting enough fuel through at idle, but i said the pumping the ball would compensate. Deferring to his experience I Got it home today and removed fuel pump, everything looked good, but I replaced what looked like a very old line from crank case to pump. Not sure if that's the pulse line as it seems to have a pulse line straight into the back of the pump from the crankcase. Can you clarify for me?

while i had the fuel pump off I. Noticed a lot of fuel on top of the bottom carb. Low and behold when you push the key in fuel was spraying from connector on top of the carb, so in essence only the middle carb was getting a trickle from the enricher and the bottom carb was getting zip. Removed the pipe and found a 1 inch tear. Cut the pipe and replaced it and low and behold the motor starts a lot easier!!!

must have happened when they adjusted the float on the bottom carb as it wasn't there when i sent it in...

noticed that the idle mixture screws are now only 1 turn out from the lightly set. Does that sound right? I'm operating at 6000 foot above sea level.

I'll also replace the check valve on the oil tank.

Last quick thing, can you tell me what the maximum WOT rpm on this motor should be? I'm running a 19p stainless prop at around 53 mph at 5000rpm
 
Last edited:
The pump likely gets a pulse from one crankcase and also one from the crankcase next to it.-----------So 2 pulse inputs to the pump.
 
...noticed that the idle mixture screws are now only 1 turn out from the lightly set
Click to expand...
I hope that they added 1/8 to 1/4 turn CCW from smooth idle point so it runs slightly rich.
 
All idle mixture settings are 1-1/2 turns ± 1/4 turns from a lightly seated position.That engine also has a thermal air valve on starboard head which make engine run rich until it reaches temp so no need to bump the mixture, also limiter caps should be in place to keep you for adjusting needles more than a 1/4 turn..
 
All idle mixture settings are 1-1/2 turns ± 1/4 turns from a lightly seated position.
Click to expand...
That's why 1 turn out concerned me. I guess it needs less fuel at 6000 foot above sea level.
 
Hi Guys thanks for the replies. Can confirm only one turn out, no extra for richness etc. confirm motor has thermal air valve, but no limiter caps installed, guess they got lost/removed at some point.

Picked up a contact at Mercury last night on a local site and he said that 1 turn plus and 1/8 is the ideal at the this altitude to ensure a little richness on a standard motor for the purposes i am using it. I'm going to go with this and try to get my hands on some limiter caps.

thanks again.
 
Hi Guys. Quick update. Motor now dialled in well. Turn 1 and 1/4 from lightly set.

Also replaced plugs with the correct BU8H's and after fixing the enrichner pipe I spoke about above it starts like a dream in less than 5 seconds from ice cold.

My new starting procedure is: Pump Bulb hard, Turn Key on and push in for 10 seconds then release and crank till it fires......

A small vid attached for anyone who's interested.
http://www.youtube.com/watch?v=69Ty0g4a-gs&feature=youtu.be
Cheers.
 
I thought so too, but that seems to flood the motor. if I go near the "primer" when it's running it splutters and dies...
 
Key is to be pushed in while cranking it over.--A motor in good condition , with the correct procedure will start right up.-----Have you checked the starter / battery cables ?-----A slow cranking outboard may not have hot spark for instant starts.
 
Last edited:
Back
Top