Merc 470 3.7 Warm Start Troubles

[natemoore]

Re: Merc 470 3.7 Warm Start Troubles

That makes sense Nate, but that is what they sold me at the autoparts (I know, I know...) store. It even says it is for fuel lines. I am definitely willing to try something else. What did you have in mind?

I was going to suggest getting some asbestos fiber out of an old building and wrap it like they do pipes in Navy ships, but your way sounds good, too.

 

[Propeye]

Re: Merc 470 3.7 Warm Start Troubles

For what's worth, I purchased a boat last summer with a 470R in it, and it too was a bear to start after it was warm. This spring I took the carb apart to check the float, needle and seat and discovered that the float level was WAAAYYYY off from spec. I only mention this because you say you rebuilt the carb, but did you ensure the float sits proper? In my case, the float looked new and I think a well intentioned previous owner overlooked the adjustment specs when installing it.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Well, so much for the optimism. She started easier when I was just motoring around the lagoon last week. However, I went fishing this weekend and put a little more heat on her. It was about 15 miles to our fishing spot (5 miles out and 10 miles north) and while the engine did not get above 140 F, the engine compartment obviously got warmer than it does for my normal 15 minute tube and skier tows. The old problem came back. It started every time with the old 1/3 throttle trick, but the boiling fuel/flooding smell was back.

I guess I will try the spacer and replace the float as Propeye suggests. The carb was rebuilt last summer, but we did not replace the float since it appeared to be in perfect condition. I guess if it even soaked up a little fuel (or was adjusted wrong), that would be plenty to screw things up

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

How about wiring in a bilge fan that runs automatically when the engine is running? You could wire up a relay to turn it on when the key is turned to run, that might vent the engine compartment enough to remove the fumes and keep things a little cooler.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

How about wiring in a bilge fan that runs automatically when the engine is running? You could wire up a relay to turn it on when the key is turned to run, that might vent the engine compartment enough to remove the fumes and keep things a little cooler.

Terry, dumb question, but what is the difference between a bilge fan and a blower? Does the fan circulate air in the engine compartment (or maybe suck in fresh air from the outside) while a blower sucks air out of the engine compartment?

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Did some research and found where a guy had the fan blow directly onto the carburetor and said it helped a lot.

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

Same thing but you could rig it up to run when the engine runs and shut off when you shut down, so you won't leave it running and discharge the battery. Yes it would suck in fresh air and blow hot air out of the engine compartment. You should have vents on the sides of the boat for the blowers. I am just worried about the buildup of the gasoline fumes, could be bad news. You could also just run the blower all the time that might help.

 

[1977 SILVERLINE]

Re: Merc 470 3.7 Warm Start Troubles

Is your fuel tank in the front of the boat or in the rear? My silverline is in the front and the pump had a hard time sucking hot fuel from the front to the back, so i installed an electric fuel pump in the front by the tank to push cold fuel to the carb, which made it start much easier when hot.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Is your fuel tank in the front of the boat or in the rear? My silverline is in the front and the pump had a hard time sucking hot fuel from the front to the back, so i installed an electric fuel pump in the front by the tank to push cold fuel to the carb, which made it start much easier when hot.

The fuel tank is right in the middle and fuel is picked up only a few feet from the carb. I will look into insulating the section before the fuel pump.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Well, I took a tip from Terry and installed a second blower -- sucks in fresh air and blows directly on the carburetor. Hopefully that will cool things off a bit.I have read about people doing this successfully on cars. Heading to the lake for a few days. I will let you know how it works.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

...and by the way, I fixed the flooding a bit. I replaced the float and found the old one was about 3/8" too low. The guy who rebuilt the carb last year must have measured from the wrong part of the float.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Well, finally solved!!! Just got back from 3 days on the lake and she started right up at the turn of the key time and time again. The new blower did the trick.

 

[nola mike]

Re: Merc 470 3.7 Warm Start Troubles

Was it the blower or the carb adjustment?

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

I ran it once after the carb adjustment, but before the 2nd blower. Cold starts were easier and the gas smell was pretty much gone. However, warm starts were still very slow, maybe worse than before the adjustment.

I think that once the vapor lock was gone, the carb adjustment helped with both cold and warm starts.

 

[SDSeville]

I know this is an old thread, but I just wanted to update it.

While the carb adjustment and 2nd blower did help things quite a bit, it was still not starting as quickly as I would have liked when warm and the gas smell never completely went away. It turns out that, in addition to my other problems, my fuel pump had a blown diaphragm and was pumping gas up the overflow tube into the carb causing flooding, especially at low RPM and just after stopping. I installed an electric fuel pump and it now starts in a fraction of a 2nd when warm. No involved routines or anything. Just turn the key and fires right up. Fuel smell is gone also.

 

[stonyloam]

Great work SD. It sounds like electric is the way to go for the 470, since there is so much trouble getting the mechanical pumps to work. What pump did you use? I may upgrade mine to electric to see if it helps my warm starting, which is not too bad but could be better.

 

[SDSeville]

Thanks Terry. The pump is a Sea Choice (made by Facet) 20301 - Gold Flo High Performance Fuel Pump 5.5-4.0 PSI.

 

[AMD Rules]

I know this is an old thread, but I just wanted to update it.
While the carb adjustment and 2nd blower did help things quite a bit, it was still not starting as quickly as I would have liked when warm and the gas smell never completely went away. It turns out that, in addition to my other problems, my fuel pump had a blown diaphragm and was pumping gas up the overflow tube into the carb causing flooding, especially at low RPM and just after stopping. I installed an electric fuel pump and it now starts in a fraction of a 2nd when warm. No involved routines or anything. Just turn the key and fires right up. Fuel smell is gone also.

Any chance you could/would shoot a video now that you have it starting well? I'd like to use it as a comparison once I stuff mine back in the boat this weekend.

I have no idea what to expect from this adventure I've been on, but it will be nice to at least try and get back on the water again So glad to hear you've overcome the hurdles with the fuel & starter issues. CONGRATS! My motor was puking a huge amount of slimey/oily blow-by out the valve cover vent since the day I got it... it will be interesting to see if it does it now. Took me a few days to clean up the back of the boat storage areas and bilge areas (I never knew it was supposed to be white! lol

Lastly, did your gas tank cavity in the hull have a drain to the bilge originally? Mine doesn't and the tank has been in a full bath of water forever... no wonder this thing is rotton! I drilled a hole now (horizontally, not vertically...lol ), for a drain. Just curious what yours had originally. This hull had a drain that passed beneath the fuel tank cavity up to the ski locker area etc.

Keep in touch..

 

[SDSeville]

Hey Chris, Yes, I will shoot a video the next time have her on the water. That should be tomorrow or Monday. As you know, they always start great on muffs.

My boat came with a drainage hole in the middle of the bulkheads between motor and tank and between tank and ski locker. I am not sure if the holes were factory or drilled by PO. What it didn't have was drain holes from the outside of the stringers to the center where the water could drain to the bilge.

Yes, I seem to have the boat running great just in time for our week on Lake Mohave. However, as luck would have it, my son broke his ankle last week at football practice and we had to cancel the trip. Oh well...

Let me know how the engine install goes.

 

[bspeth]

Nate,that stuff reflects the heat away from whatever part you wrap with it,on my jeep I wrapped my clutch slave cylinder which is about 1/4' from my exaust and it works like a charm.