Merc 470 3.7 Warm Start Troubles

[SDSeville]

My 1986 3.7 starts perfect when cold, idles great, and runs like a champ all day long. However, the warm starting is giving me fits. It always starts, but usually takes forever and feels like the choke is on or it is flooded. I have tried pumping the throttle one time before I turn the key to turn off the choke, but that doesn't change anything. I had the carb rebuilt recently and it did not affect the warm starting. Points, plugs, and wires new last season.

Is it crazy to think that I should be able to just turn the key and it starts right up like my truck?

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

You might try using the throttle only button and giving it about 1/3 throttle when you try to start. Back off as soon as it catches.

 

[zlman1970]

Re: Merc 470 3.7 Warm Start Troubles

Vapor lock? Before you try restarting after its warm, pour some lake water on the line once. If it fires right up, you have vapor lock issues. Mine did this, found some self adhesive foil lined wrap at the hardware store. Wrapped the last 8-10" to the carb. So far problem solved.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

Thanks guys. I will give this stuff a shot this weekend and let you know how it goes. Terry, I usually do the opposite of what you suggested -- about 1/2 throttle (throttle only) and move forward as it catches.

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

Thanks guys. I will give this stuff a shot this weekend and let you know how it goes. Terry, I usually do the opposite of what you suggested -- about 1/2 throttle (throttle only) and move forward as it catches.

Yeah whatever works LOL. Sometimes I do the same, mine can be a little stubborn too. I did switch to 89 octane non-ethanol gas and that seems to help starting and it runs great.

 

[Old Yeller Boater]

Re: Merc 470 3.7 Warm Start Troubles

That's what I have to do when warm as well. about half throttle, and usually work it to full and pull back as I'm cranking until it catches. I've not gotten the carb checked out yet though, so will be listening in on this thread to see how it goes for you SD.

 

[zlman1970]

Re: Merc 470 3.7 Warm Start Troubles

Yeah whatever works LOL. Sometimes I do the same, mine can be a little stubborn too. I did switch to 89 octane non-ethanol gas and that seems to help starting and it runs great.

Non-ethanol gas is pretty much a thing of the past around me. I hope $8-9 corn will ease production

 

[Brewman61]

Re: Merc 470 3.7 Warm Start Troubles

I hope $8-9 corn will ease production

Don't hold your breath on that one. They'll just use it as yet another excuse to push up the price of gas.

 

[carguy001]

Re: Merc 470 3.7 Warm Start Troubles

I also have a 470 and have had the same issue with hot starts i rebuilt the carb which helped but what really made the differance for mine was setting the float about 1/32" lower than spec and wraping the fuel line with insulation and foil tape. I do have to crack the throttle about 1/2 way

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

I will be trying the tape this weekend. It makes sense that it should work. It gets hotter than hell in that doghouse.

 

[Old Yeller Boater]

Re: Merc 470 3.7 Warm Start Troubles

+1 to that. HOT! I won't have a chance this weekend, so let us know how it works for you.

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

I will be trying the tape this weekend. It makes sense that it should work. It gets hotter than hell in that doghouse.

Run the blower when you are going slow.

 

[whatsagm]

Re: Merc 470 3.7 Warm Start Troubles

Mine was doing the same thing. I found that the starter and battery were my problem. The starter was drawing so much juice that it was not providing enough power to the ign system. I replaced the starter and it was good for a while but it came back. I then tested my battery and found I had a bad cell. Replaced it with the biggest battery i could find. All hot starting issues were gone.

 

[Old Yeller Boater]

Re: Merc 470 3.7 Warm Start Troubles

Run the blower when you are going slow.

I did that last weekend. didn't seem to make a difference for me. Worth a shot though.

 

[wrestling coach]

Re: Merc 470 3.7 Warm Start Troubles

I have found that less throttle is better than more throttle starting my 470. Cold start. 1 shot 1/2 throttle then return throttle to just cracked open. Turn key and it starts in 3 seconds. Warm start. Just crack throttle. Turn key and it starts instantly. Using series 27 marine cranking battery with Pertronix ignition and coil. Non-ethanol fuel.
In addition,when practical, after a long run up to full operating temp about 190*, I let the engine idle in neutral as the temp falls back to 160* at idle. Then I shut it off. Don't know how important that is but it works for me.

Dennis

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

I have found that less throttle is better than more throttle starting my 470. Cold start. 1 shot 1/2 throttle then return throttle to just cracked open. Turn key and it starts in 3 seconds. Warm start. Just crack throttle. Turn key and it starts instantly. Using series 27 marine cranking battery with Pertronix ignition and coil. Non-ethanol fuel.
In addition,when practical, after a long run up to full operating temp about 190*, I let the engine idle in neutral as the temp falls back to 160* at idle. Then I shut it off. Don't know how important that is but it works for me.

Dennis

Just cracked?
Interesting...maybe I have been causing the choked/flooding sensation myself by applying throttle when I don't need to.

 

[stonyloam]

Re: Merc 470 3.7 Warm Start Troubles

In addition,when practical, after a long run up to full operating temp about 190*, I let the engine idle in neutral as the temp falls back to 160* at idle.

If you are running at 190 and it drops to 160 at idle IMHO you have a cooling problem. It should run at about the same temperature across the entire RPM range.

 

[wrestling coach]

Re: Merc 470 3.7 Warm Start Troubles

If you are running at 190 and it drops to 160 at idle IMHO you have a cooling problem. It should run at about the same temperature across the entire RPM range.

Let me be more specific. This is a Grady White temp gauge as I think you know. Lowest temp on the gauge is 100 and has a blue line. 150 is straight up and has a blue line and 240 is the highest temp and has a blue line. Half way between 100 and 150 is a white slash no number I assume that to be 125. Half way between 150 and 240 is a white line and I assume that to be 195. At idle or low speed like trolling the gauge is just off the blue line of 150. It has a 160 stat so that appears to be correct. Running at 3000 rpm for awhile the temp will run up but not on or near the white line I assume to be 195. I was just guessing a max of 190. Probably closer guess would be 180-185. The gauge does bounce around a bit and is not always steady at higher RPM's so it can be hard to read. I have an IR gun and I should shoot the area around the cap at 3000RPM and see what it says. I will do that this weekend.

 

[Old Yeller Boater]

Re: Merc 470 3.7 Warm Start Troubles

I will be trying the tape this weekend. It makes sense that it should work. It gets hotter than hell in that doghouse.

Let us know what tape you use. I got some adhesive foil backed insulation from Lowe's that I used on my camper water lines with a heat tape wrapped up inside. it's held up to weather for two years now. I was thinking that might work for the fuel line, but curious to know what you're going to use.

 

[SDSeville]

Re: Merc 470 3.7 Warm Start Troubles

I bought this stuff from O'reilly yesterday.

http://www.oreillyauto.com/site/c/d...p?ck=Search_heat+tape_-1_-1&keyword=heat+tape

It specifically mentions fuel lines. Too bad it is only sold in 15 foot rolls -- $18 for way more than I will use. It will be well worth it if it works. I will take some pics of the install and let you know how it works.

Any thoughts on how many layers I should use?