Help w/ fuel issue

[TRD]

Hi all, I am having an issue w/ throttle up on the boat. I got it running but when I hit the throttle I get about a 2-3 sec hesitation. It will run fine at once it gets going but if you back off the throttle it will run rough or cut off. Then it doesn't want to start. I have to put in neutral and force the throttle linkage open all the way and 5-10 sec. later it may start. Black smoke comes out, as long as I keep the RPM's up it runs. I did fog the engine the last 2 years. This started last year the last time I took the boat out also.
I have a 2000 350 MPI w/ 315hp. Plugs were change last year, fuel/seperator changed yesterday. Took out about 10 gal. of gas and put 10 new in. I got some Lucas fuel injector cleaner going in today (if it stops raining). any suggestions? Is there a fuel regulator on this boat?

TIA

[dogbert]

Yes and if you've never changed it, you probably need to. Mine went out a couple of years ago. On a V-Drive it's a pain to get to. It'll be on top of the fuel cooler (port side of engine on your boat). It's a diaphragm and because of the ethanol requirement in today's fuel, it tends to disintegrate after a while. I had an alarm go off at higher RPMs.

However, that wouldn't cause it to run rough. I'd check your distributor cap. Our mercs are notorious for going through distributor caps. It sounds more like a timing/spark issue than a fuel pressure regulator issue.

I replace my distributor cap as often as I do my impeller.

[chpthril]

Could be that the CTS (coolant temp sensor) is unplugged or faulty, Not sure if that engine has a MAP (manifold absolute pressure) sensor, if so, check the vacuum line running to it for leaks. If it has a fuel rail mounted fuel pressure regulator, check the vacuum line for fuel.

[TRD]

we ran the boat today and it did run better w/ the new gas. We are going to put more new gas in tomorrow and see what happens. I will also check these other items. It still ran rough at times but did run better.

Thanks again.

[TRD]

Well I added 10gal premium gas today and it did run better. It still has a hesitation and doesn't run at full throttle. It does run good at boarding and surfing speed. What will bad gas do to my injectors? If the boat does stall I have to pull my pin and push the throttle all the way back to open my butterfly so it will start.

Chp, not sure what you are telling me to check. I think I do have the rail, is this what the injector are conected too?

Thanks

[chpthril]

Well I added 10gal premium gas today and it did run better. It still has a hesitation and doesn't run at full throttle. It does run good at boarding and surfing speed. What will bad gas do to my injectors? If the boat does stall I have to pull my pin and push the throttle all the way back to open my butterfly so it will start.

Chp, not sure what you are telling me to check. I think I do have the rail, is this what the injector are conected too?

Thanks

Spoiled gas is more of a nuisance then anything, if caught early. A fresh tank of gas or 2 and a bottle of additive, such a Sta-Bil will clean any varnish left behind, which would be very little, if any, after only a few months of storage.

Yep, the injectors are attached to the fuel rail. If it has a rail mounted regulator, you will se a vacuum hose attached to it. Pull the hose and see if it has fuel in it. If so, diaphragm is bad.

[TRD]

ok,
so do you think I have a bad gas problem?

we got caught in the rain again today. sorry you missed it.

[chpthril]

ok,
so do you think I have a bad gas problem?

we got caught in the rain again today. sorry you missed it.

Maybe a little bit of 2 issues. Did you use any kind of winterizing fuel additive last fall when you put it away? The black smoke indicates a rich running condition, not typically associated with spoiled gas.

[TRD]

Yes I did. There may be a chance I didn't have the tank full after all the gas we put in. I may not have put enough of stabil in also but not sure. I need to look for the fuel regulator and the diapham thing.

[TRD]

Here is a picture of my "Mercruiser Cool/Fuel" it says. Is this the area the diapham is? You can see the vent tube coming out of it on the top. It goes up to the injector/butterfly area. I didn't see gas coming out that end when I pulled it off, but does the engine need to be running for this? I did turned the key on a couple of times.

On the back of the injector rail I did see some kind of sensor w/ wires coming out, how could I check this thing? I can take a picture if needed. On the bottom of the carb/butterfly area (don't know what to call it) there are also other sensors, what could they be for? I know I should have taken more pictures. sorry for the poor explaintion.

[chpthril]

That is deffinetly the fuel pressure regulator. You may want to have ot running to be 100% sure no fuel is leaking past the diaphragm.

[TRD]

Is it the top part? this is the one w/ the vent hose going up to the top of the engine. It looks oily up on the top side at the end of the vent hose also.

Where would I look for something like this? would there be a p/n on it?

Thanks

[dogbert]

Is it the top part? this is the one w/ the vent hose going up to the top of the engine. It looks oily up on the top side at the end of the vent hose also.

Where would I look for something like this? would there be a p/n on it?

Thanks

Check the link in this thread for the part number. You can probably even find the exact location of the fuel pressure regulator. There's diagrams and everything. You will need your engine serial number, tho.

[TRD]

Hey Dogbert,

It looks like this is the Regulator Kit (of course it is the most expensive part). Is there anything else I need to look at here?

I haven't done Chp test yet w/ the engine running, but plan to over the wkend. Is there any other way I can be sure this could be my issue?

also, where exactly would the serial # for the engine be?

Thanks

[TRD]

Is there a OBII connector on my engine that I can hook up a code reader too?

Thanks