Boat won't start when warm

[Puddy905]

Ok. I'm on my last straw here. Next step is driving out in the middle of the lake and pulling the plug if you know what I mean. I've had several posts regarding this issue and nothing seems to fix it. After going out for a cruise, letting the boat sit for a bit, and then going to restart, it does not want to start.
Here's what I have done to remedy:
Originally I thought vapour lock, so I have updated cooling and fixed all ventillation issues, which keeps the engine area nice and cool all the time.
On top of that, I have done a complete rebuild of the carb, resetting float levels, replaced filter, and all that jazz.
I replace the fuel pump and filter.
Replaced the entire thermostat housing to a new style that accomodates the newer thermostat style (so thermostat has been replaced as well).
So, after doing all this, and still having the same problem I went electrical.
I replaced the Ignition module and ignition coil.
Timing is good. Idles great. Runs great. Doesn't start when warm.
I'm getting really pissed off.
The only thing I noticed today was when I stayed on the ignition, it did try to start after 15-20 seconds of cranking, and I could smell fuel, which is making me think that stupid electric choke, but last year, I adjusted it all the way back (so it barely does anything) and that didn't help.
So.....it's either beyond my control, OR it's operator error. Please tell me YOUR starting procedure when the boat has run that day. Do you give it any throttle before hand? Do you push the throttle only button and move the lever forward a little before cranking? Do you crank and crank and crank until it starts?
The funny part is when it's cold (sitting overnight) I give it a couple shots of fuel and cranked for 3-5 seconds and it fires right up.
If someone can help me, you will be my new best friend!

 

[smassey22180]

Re: Boat won't start when warm

My 3.0 will not start easily when warm unless i give it a just the amount of gas. I always use throttle only button and then push it just a hair past the indent. The indent is where it would stop if you were gently pushing it into gear. It then starts instantly every time. Not enough gas and it is pretty slow to start. If I accidentally pump the gas it floods and is very hard to start.

I would run the boat to warm it up, shut down, remove the spark arrestor and view down the carb to see if fuel was leaking after the engine was shut off. Replacing the fuel pump without the correct shim can increase pressure enough to cause this.

Next time you crank it warm, push down on the throttle while it is trying to start. If It starts close to full throttle that may be an indication of flooding. That is the Mercruiser approved way to start an engine if flooded .

 

[smassey22180]

Re: Boat won't start when warm

From the 3.0 owners manual

Place control handle in NEUTRAL. Position throttle setting as follows:

COLD ENGINE - Move control/throttle lever to full throttle, then return to about 1/4 throttle. In extreme cold it may be necessary to pump lever more than once.

WARM ENGINE - Move control/throttle lever to 1/4 throttle position.

FLOODED ENGINE - Move control/throttle lever to full throttle. Be prepared to decrease engine speed to 1000-1500 RPM as soon as engine starts.

 

[Puddy905]

Re: Boat won't start when warm

Thanks guys. Got it started under WOT. Just don't think it should get to this. I will check the carb for leaks tomorrow. Everything to me is pointing to flooding over not enough fuel. When I have it a the dock and just idling and shut it down it will fire up everytime no problem. When I go out for a ride and come back and either let it idle or not it won't restart.
Strange

 

[alldodge]

Re: Boat won't start when warm

Recheck the float level, and try to see if you float is sinking. Pull it out and weight it if you have a gram scale, not sure you would have one. Find out what it weights now and after four to six hours. It should be the same.

If you don't have one put a table knife on edge in a bench vice. Get a hack saw blade and find the balance point in the middle of it. put the float on one end and find items like washers to place on the other until it is balanced. Wait four to six hours and it should be real close to the same. It will move but something like a feather should keep it balanced once the gas on the surface evaporates. For best results put the float in gas weighted down where it is below the gas and let is soak for a few hours. No float should absorb any gas, then find the balance point.

 

[bonzoscott]

Re: Boat won't start when warm

Just some thoughts as we can see your frustration - When ever this occurs, check for spark (inline spark tester). Try what Smassey said, 1/4 throttle when warm. One other thought, run the boat a bit (5 minutes) at idle after hard run and let it cool.

 

[Puddy905]

Re: Boat won't start when warm

Thanks for the suggestions. I will start with the easier stuff in the morning and work my way through all your ideas. Obviously pulling the carb apart again will be towards the bottom of the checklist. ;-)

 

[Oshkosh1]

Re: Boat won't start when warm

Use a 1/4" Phenolic spacer between the carb and manifold to eliminate the heat sink effect. Along with that I used pipe insulation wrapped with metal duct tape to shield the exposed fuel line. Worked for me.

 

[mmcconn2]

Re: Boat won't start when warm

I had a similar issue and checked all the same things you are going through. I found that the cooling in the engine compartment was not as cool as I thought. After you run the boat and stop, open the engine cover while the boat sits, then try to start when you are ready to go. I found that the way my fuel lines were run that the heat from the engine and the heat from soaking under the closed hood would evaporate the fuel from the lines. mercury does have a bulletin out on this issue and they sell a kit to fix the problem. but try opening the engine cover and see if the issue goes away. this is a no cost test and its easy to do. Good Luck!

 

[alldodge]

Re: Boat won't start when warm

There are two differnt things being discussed.
(1) The original post stated you smell fuel and later you can start it using WOT position If this is the case then there is to much fuel present, flooding comes to mind.

(2) Folks are discussing vapor lock which results from not enough fuel. Open hatches, insulate your fuel lines, keep the blowers running when stopped, try to get fuel without ethonel, don't use pump gas and diffently no winter fuel blend.

Hope you guys can figure it out because they don't go together.

 

[Puddy905]

Re: Boat won't start when warm

So today I adjusted the idle air screw as lean as I could and found I was over a turn too rich, so that may have been contributing to a "flooding" effect. Also, I used the starting procedure posted all day and it seemed to help. The problem hasn't surfaced today, but the temp was cooler outside and I didn't run wot at all today. So, I'm gonna try it over the next few days and I will repost to let everyone know how I made out.

 

[Puddy905]

Re: Boat won't start when warm

I did notice today however that my throttle cables may be out of adjustment. I find that when I slowly move the handle back and forth, I am getting different rpms in the same spot. Like the throttle is "sticking". I did have the cables completely off when I refueled the interior, so maybe I put them back wrong? I have no clue how to adjust the cables at the controls. The only adjustment I know is the actual throttle cabl at the carb.

 

[Puddy905]

Re: Boat won't start when warm

There are two differnt things being discussed.

(2) Folks are discussing vapor lock which results from not enough fuel. Open hatches, insulate your fuel lines, keep the blowers running when stopped, try to get fuel without ethonel, don't use pump gas and diffently no winter fuel blend.

Hope you guys can figure it out because they don't go together.

Dodge,
I did originally think it was vapor lock, but as you suggested, I have improved ventilation, and insulated lines. The temp in the engine compartment doesn't get hot at all anymore. So, that's what lead me to troubleshoot other areas.

 

[OldNBold51]

Re: Boat won't start when warm

I'm with you on the flooding/ rich condition. Were I you, I'd adjust my idle screw's , once warm, until I got max rpm's from engine. Every engine runs a bit different and the OEM recommended settings are a starting point, not an absolute.

 

[Mule Laker]

Re: Boat won't start when warm

My 3.0 will not start easily when warm unless i give it a just the amount of gas. I always use throttle only button and then push it just a hair past the indent. It then starts instantly every time.

That's exactly how my 2007 TKS 3.0 is. It's very frustrating.

Puddy, when you do start yours this way can you immediately move the throttle back to neutral and have a good idle? Mine will always start with the above procedure but if you move it back to idle the rpm's just aren't high enough, about 500 which shakes the whole boat. My carb is clean, the motor runs strong and smooth, and starts up easily when cold. Like I said, it's very frustrating.

 

[Puddy905]

Re: Boat won't start when warm

As long as its warm, yes I can bring it right back to neutral position and it will idle around 750-800 rpm, which I set to the manual. When eased into forward it will drop down to 650-700 which is also by the book. It runs perfect. Just starting is the issue. Seemed to be ok yesterday.

 

[Puddy905]

Re: Boat won't start when warm

It's good to hear that this seems to be a fairly common thing. Thanks for all the comments everyone.

 

[Mule Laker]

Re: Boat won't start when warm

As long as its warm, yes I can bring it right back to neutral position and it will idle around 750-800 rpm, which I set to the manual.

Hmm. Looks like I may be the one with a problem.

 

[Puddy905]

Re: Boat won't start when warm

Update. So after a week of cruising, skiing, tubing, etc i have had no more starting issues. I believe it was a combination of the idle air mixture being to rich and error on my part in regards to the starting procedure. I think I've got it now and should be good.
Thanks to everyone who chimed in.

 

[NHGuy]

Re: Boat won't start when warm

Aah, carburetors. They are old school, like me. Glad you got it worked Puddy.
Mule Laker do as Puddy did, set your idle mix between stumbling and too fat. Then if too high, get your idle down to specified rpms and recheck the mixture.
If it still runs rough on a hot start let us know in a thread of your own.