5.7lt hard to start after a small run and 30min sit but still starts - Maxum Boat Owners Club

fatboy.1234 · 09-01-2010, 09:29 AM

hi guys , i took my 2400scr with 5.7lt carb engine out last week end and every time i stoped i found it took 20 to 30sec to start ? but when i do a first start up it starts up 3 to 5 sec?? has any one had this problem??. someone told me it could be my lifters loosing pressure, but if that was the case it should take the same to start first time after sitting 2 to 3 weeks??? thanks.........................

ss3964spd · 09-01-2010, 02:49 PM

Fatboy (sheeesh, difficult addressing you, what's your real name!),

Not sure where people come up with some of these ideas but I assure you that the hard re-start symptom is not a result of your lifters loosing pressure.

Question: How much time passes between shut down and restart attempt(s)? 2 minutes, 5 minutes, 30, 60, etc? Does it happen every time? Easily reproduced? Give me a scenario.

Dan

fatboy.1234 · 09-02-2010, 12:26 AM

hi dan its Ben,
it might be sitting for 10min to 2hr as for re-star 2 to 5 min rest in between cranking
and it happens everytime but say i go for a run 20min then shutoff for 1hr it will take me 20to30sec to re-start at full cranking non stop but once its starts no problems,
but after i trailer it home 30 to 40min to flush it out it starts with half a crank?? and first start it only takes half a crank to start

thanks Ben................

ss3964spd · 09-02-2010, 02:24 PM

Given the symptoms you've described Ben, two possabilities immediately come to mind.

1) It almost sounds like vapor lock, which happens when the gas in the fuel line from the fuel pump to the engine gets heat soaked. Engines actually get hotter when you shut them down. Have a look at the line from the pump to the carb (it's probably a metal line) if it is routed close to the engine block. A quick and dirty test is to wrap the line with wadded up tin foil. The foil will reflect the heat, and having it crinkled up will create small voids where air gets trapped and further insulates the line.

However, since you mention you experience the symptom a hour after shut down, that line should have cooled sufficiently by then so I don't think that's the problem.

2) I think the carb may be leaking gas into the engine after shut down, thus flooding the engine. When this happens the intake manifold plenum, just below the carb, pools with gas, the engine gets hotter after shut down, that pooled gas vaporizes but remains trapped in the intake because the carb throttle blades are closed. When you try to restart the gas/air ratio is way off - too rich, and the plugs can't fire it. So, a quick test. Run it until it's warmed up then shut it down. Wait for oh, say, 10, 15, 20 minutes - or 1 to 2 beers. Before attempting to restart depress the neutral button on the throttle/shift control so that you can open the throttle without the drive being in gear. Open it all the way and then hit the key. If the engine starts quicker then you've found the problem (the carb float/needle/seat). Once the engine starts be quick to pull the throttle back to idle, least you over rev the engine. You could also run it, shut it down, then quickly remove the flame arrestor from the carb and, with a flash light, look into the carb for signs of gas bubbling/dripping, etc. There should be none.

Oh, thought of something else. You did not mention what type of ignition system the engine has but if it's the type that has an electronic module inside the distributor there is a good chance that the EM is becoming heat soaked, rendering it inopperative until it cools off. Very common.

Good luck, let us know what you find.

Dan

fatboy.1234 · 09-03-2010, 12:16 AM

thanks , i will try it this wekend and i will have a look at the em and let you know what happend
thans Ben...............

shrew · 09-03-2010, 01:50 PM

Did we establish whether this is a carb or fuel injected engine? I think it would help to confirm that first.

fatboy.1234 · 09-05-2010, 04:15 PM

hi , it was a carb engine

Le Miss Tiffany · 09-06-2010, 08:57 PM

I'll have an 1992 Maxum SCR 2300 with the exact same problem, and my mechanic told that I need a new carb kit, my motors runs at 400 to 500 RPM on iddle, no problem at all when I cruise with it, its only when I shut the motor for few minutes, like when i did more than one locks, everytime when I start it back it took me 10 to 15 sec before it fire on ... So I wait for the end of the season before a big tune up ... I hope this is help!
Hey Fatboy (Ben) let me know if you fund the problem!
Thanks
Erik

fatboy.1234 · 09-09-2010, 08:40 AM

hi ,
so le miss tiffany did this fix it??
i wend out this week and i tryed to start it with some throttle but still same problems , i ended up just cranking it over untill it started but once it did i was fine but then wether turned to 7ft waves and it was a long slow drive back to dock.
i also spoke to a v8 rep today ad he said the float might be getting soaked?? he said i should rebuild the carby ,has any one herd of this
thanks Ben...................

ss3964spd · 09-09-2010, 02:09 PM

Don't try it with some throttle Ben, try with ALL throttle - IE; completely wide open. If the engine is getting "flooded" with gas then the gas to air ratio is way off and the spark plugs can't fire the rich mixture. Opening the throttle all the way allows more air into the engine thus bringing the gas-to-air ratio back in line. As I said thou, just be ready to pull the throttle back if the engine does start.

The Rep you spoke to is correct. Inside the carb is a chamber that holds gas. Also in that chamber is a float. As the fuel pump sends fuel to the chamber in the carb the float rises within the chamber and eventually rises high enough to stop the flow of gas using a sub-assembly called a needle and seat (works exactly like the float in a bathroom toilet). If the float gets a hole in it, or becomes saturated with gas, it won't float so it won't stop the flow of gas into the carb so the carb over fills and the excess spills into the engine.

Frankly though, you don't have enough information yet to point to carb problem, or specifically a problem with the float.

Dan

fatboy.1234 · 09-09-2010, 02:32 PM

thanks, i also tryed to start it wot and wouldnt start , what i will have to is is a full service on the engine (plugs ect..) and then see what happends from there,
the carby rebuild kit is only 70 aus dollars
thanks i will keep all posted................

ss3964spd · 09-09-2010, 03:16 PM

Ben, don't let anyone touch the carb until you've tried everything else. If trying to start it at WOT didn't work it seems to point away from the carb.

Did you check into the ignition system? From my previous post: "Oh, thought of something else. You did not mention what type of ignition system the engine has but if it's the type that has an electronic module inside the distributor there is a good chance that the EM is becoming heat soaked, rendering it inopperative until it cools off. Very common."

Dan

fatboy.1234 · 09-10-2010, 05:31 AM

dan ,
i will have to check what ignition system is in it , the bad thing is i bought the boat from the usa and shipped it over to australia and there is not much know how
on parts like whats over there .....thanks

ed & inge · 09-10-2010, 10:28 AM

hai ben......

mercruiser has a department in australia..... http://www.mercurymarine.com.au/ .....

maybe they know a good mecanic in the area you live that you can visit if you'r out of options.......

greatz, ed

Horizon · 09-15-2010, 12:19 PM

If all else fails and before you buy a new carb, Try an easy test.

There should be a check valve (one-way valve) on the pick-up tube attached to the gas tank. It looks like an aluminum hose barb screwed into an elbow attached to the tank. Follow the gas line back to the tank. They have been known to act like your symptoms when they get clogged and sticky. Temporarily remove the check valve and install a regular hose barb. If your symptoms go away it is a $15 part. If no change, replace the check valve. It should take around 15 minutes to find out and the cost of a $3 brass hose barb.

I had similar symptoms on my Merc 3.0, even rebuilt the carb. It started great ran for 15 min. died out, then hard to start. Tested the spark, coil, fuel pump, filters, came down to the check valve. The motor was starving for gas after it used the gas in the bowl. I replaced the check valve and it now runs great.

I know the others that have offered suggestions are probably more of value than mine but I thought that this may help if all else fails.

Joe

fatboy.1234 · 09-24-2010, 08:15 AM

ok just done a full service all plugs leads olis filters and new dissy cap rotor cap just in case and i draind the old fuel as well
i am going to take her out this weekend ad see how we go

jblack1036 · 09-24-2010, 01:33 PM

fATBOY.1234

Hey there, I have a 94 2400scr with the 5.7 and I have the same or similar problem. I identified my problem was the float as they said above. The give away to my problem was the smell of gas when I opened the engine lid. You might want to check that next time you go out since you haven't mentioned anything about opening up the compartment after running. It's real important that you make sure the blowers are working and let them run for a bit before you fire it up. If all that vapor were to ever ignite......well, let's just say it won't be very pretty....
If that is the case, then a carb rebuild would be the next step. Of course, it's pretty easy to pop the top of the carb and just replace the float or the neadle valve. or simply bend the float arm a little if the float isn't bad. Just my 2cents...

Good luck.

fatboy.1234 · 09-25-2010, 02:03 AM

thanks for you 2 cents it all adds up to a working boat ... and a safe boat!
thanks jim ......

fatboy.1234 · 09-27-2010, 09:32 AM

ok took it out this weekend it starts but not much as a wait but still a 10 to 20sec crank and then starts no problems
i also tryed starting it with the throtle open a little bit and it started better and only after 2 or 3 cranks
any hints
thanks Ben.........

njones · 09-30-2010, 09:46 PM

I had been experiencing a similar issue and just lived with it. (wrote it off as silly carburators) I recently decided to add a marine starting battery along with my marine deep cycle battery. Was just adding it so I could switch it to one bat and if i drained the battery while on the hook I could switch back and be able to crank. I accidentally found a issue and now not only does my engine spin over faster, but my slow to start on hot motor problem is no more. Apparently starting a hot motor was pulling my battery voltage down low enough to affect the ignition system. CCA of your battery may be something to look into.