Hello
I 'm new to the forum and I am from Norway .
I have a few problems with my engine that I wonder if you can help me with ?

My boat is a Regal 2850 lsc with a Mercruiser 502 Magnum MPI . last model.
My problem is that the engine is not running fine at idle, but runs much better over 1000 rpm . Engine is shaking alot at idle and there is a small fuel film left on the water when it is idling . Gasoline consumption I think is normal, but have not checked the fuel pressure regulator . I have changed the spark plug wires , spark plugs , idle speed regulator , checked the ignition sequence and ignition cap

The engine is almost like new and has few hours.
I have no instrument to make the diagnosis on the engine, but was hoping that someone has had similar problems who can help me to find the problem . I do not have shop nearby and have to remove the engine and send it to another city . Hope I do not have to send it.

I have some suspicions that there may be problems with the fuel injectors , but find it a bit odd since they look like New and have few hours . I have not removed them from the engine yet.

Are there any other sensors on the engine should be checked ?

Would have been great if someone could help me
Thanks!!

Anyone?

Collapsed lifter, broken spring, too much fuel psi (vac hose broke or disconnected from regulator), Vacuum leak ,low compression, weak spark in a cylinder, totally wrong spark plugs, incorrect base timing, weak alternator, shorted battery...............to name a few.

Ck for vacuum leak and then line to regulator , then Ck compression and watch compression gauage. You'll see if bad valve or piston + rings. I don't care if the engine is brand new. Schit happens.

We need some diagnostic work from you with reports back vs just parts replacing.

Sounds frustrating from the standpoint of where the boat is.

Is #8 spark plug dry or wet? Same as the others? Smell raw gas when at idle? If it is wet your diaphragm or needle n' seat in the VST is shot dumping raw gas into #8. From there you will have to take a compression test. and fallow what SB posted above

What year is the motor? Troubleshoot problems just like the other guys have stated. Compression test, fuel pressure on fuel rail, bad IAC control. If it does have a VST tank, there can be many issues that could cause this problem, so give us some more information and we can help. If you don't know how to do these tests, we can try to help you through it all if you are willing to buy some tools. Not bad investments if you are that far away from a mechanic.

If its an MPI, then it should be a Cool Fuel system and not a VST system.

You need to put a Rinda scan tool on it and see what codes are present.

Thanks everyone for your quick and good answers

Iac sensor is new, so assuming that is not it. Spark cables are new and spark plugs as well. . I use NGK BR6FS . Distributor cap and rotor are new and have also checked the ignition timing . The batteries I have are 2 pieces of 110 amps and are brand new. Have Checked vacuum hoses, and have not found anything wrong there. But also noticed a slight ticking sound from the upper part of the engine . I thought at once that it can be a bad valve lifter . Hav not change the oil yet. I use 25-40 oil.
Is a little unsure if I have the exhaust flap in the y horn that can make this sound. When I revs the engine over 1200 rpm , then the sound disappears more or less.

The engine is a 2001 mod with cool fuel system mounted right side viewed from the front , down by the engine mount , not VST .

Purchased compression test this weekend and will run a test tomorrow . Does anyone know if I need to take the test with the throttle open?

Have checked all the spark plugs if they were wet after a period of idling . 7 of them were black , indicating rich fuel mixture and 1 was brown and nice .

Does anyone know of an online store that I can buy Rinda Scan Tool that send to Norway ? Not rinda.com but a page that has shopping cart and checkout ?

thanks again

The 7 wet plugs definitely indicate it being rich. That 1 looked good is curious. Most things that would make it rich or lean would make all cylinders rich or lean. I would go forward with the compression test. It should be done with throttle fully open. What is the idle RPM? Mine had erratic idle rpm and sometimes was a bit flat at higher rpm. Ended up being a throttle position sensor. Mine wasn't really rich like yours though. I would also check fuel pressure at the fuel rail.

Sorry if I worded me wrong, but I meant "black" not "wet"

At idle it is pretty stable at 700 rpm

Do they have thermostats installed? Mine would act up at idle in colder water until I put thermostats in them, would also cause it to run rich?