Surging

[Yellow Yota]

So, my 350 MAG MPI has ran well since I got it a few months ago. Other than cleaning the throttle body and IAC, I've done nothing.
Today, I took the family out for a few hours of fun. All went well, but by the end of the evening, during a cruise across the lake (approx 4000 RPM), the motor would surge occasionally. Nothing drastic, but also not right. So, I was thinking maybe fuel filter. As I just got the boat, and it has relatively low hours on it, I haven't changed it. Figured I'd take care of that at the end of the season. Now the kicker, is that when I fired it up to get it to the trailer, it was surging at idle. When I dropped in gear, it died. Then re-started and ran fine all the way onto the trailer.



Anyone got any suggestions or experience with a similar situation?


Thanks,
Chad

 

[havasuboatman]

Re: Surging

Replace your water separator, you likely have water in it. If not that, surging is caused by fuel starvation when it happens only at high rpms, the another cause is a vacuum leak. (when it occures at all rpms)

 

[Yellow Yota]

Re: Surging

I am going to get a filter/separator in about 5 minutes. Looks like a messy job!
I was thinking fuel starvation (filter problem) at the higher RPM, but was a little confused at low RPM because it was intermittent.

Thanks much for the reply!

Chad

PS. I'd heard that boats are nothing more than holes in the water into which you toss money. Apparently that's true! Apparently it's still new enough to me that I don't mind yet!!!

 

[Yellow Yota]

Re: Surging

Replaced the spin-on filter with a new one. Parts guy thought I might have another filter, but I can't find the round in-line one he thought it might have. Maybe I only have one? Hope so, because the other one was 5 times more money!

On a side note, I also installed my Smart Tabs. Can't wait to try them out!

 

[Yellow Yota]

Re: Surging

DAMMIT!!!

So, I hooked the hose up, and started the motor. I was surprised that it started easily since there had been a break in the fuel line while I installed the new filter. Figured the air in there might make it tough to start.

It ran fine for about a minute, then died. Had a heck of a time getting it started again. Took several tries to get it to keep running. I vented the fuel line, trying to get the air out, by releasing the schrader valve. (Not sure if this helps or not. I'm a diesel guy, so I know that fuel and air don't mix. At least in a diesel.)

Got it to idle OK, but if I try to blip the throttle, it backfires and pops.

I'M SO FRUSTRATED!!!

This thing ran great for the last couple of weekends, and is now a pile.

Am I looking at injectors? What are my options? My only local boat shop will only tell me it will cost $90 per hour to diagnose. Can't even give me an estimate to tell me what is wrong! Might be one hour, might be 6. Unfortunately, I need a little more info than that before I start shelling out cash just to give me an idea of what's wrong.

Sorry to vent. i'm just angry.

Any help is mucho appreciated.

Thanks,
Chad

 

[Fun Times]

Re: Surging

What is your engine serial number? What year is your engine?

You will need to get a fuel gauge hooked up to that schrader valve, It should be around 43 psi.

 

[cr2k]

Re: Surging

YES you need to check fuel pressure. Could be fuel pump.

 

[havasuboatman]

Re: Surging

Take the fuel filter back off, fill it to the very top with gas, re-install and try it again after cycling the fuel pump a couple of times. (bleeding the schrader each cycle.) and hope you didn't kill the fuel pump running it dry.
ALWAYS FILL YOUR WATER SEPARATING FUEL FILTER BEFORE INSTALLING IT!!!

 

[Yellow Yota]

Re: Surging

Guessing the filter is full by now! I took it out and ran it for about 20 minutes. Seemed to run OK for a while. Had a hell of a stutter when I gunned the throttle fast. Like a bad accelerator pump on a carb'd motor.
After a bit, my top speed dropped from 48 to about 42!
Engine #: OM648967
Boat is a 2004 Rinker Captiva 212 RX1 model

I will make sure to fill the filter next time. I thought about it, but didn't do it.

On the plus side, the Smart Tabs ROCK!!! Almost no bow rise getting out of the hole, and much faster on plane. My minumum plane speed dropped to about 16 MPH from about 20-21. Porpoising is also non-existant. Can't wait to use them more when my motor runs right!!!

 

[Yellow Yota]

Re: Surging

I knew there was a reason I didn't fill the filter first! I read the FSM! Nothing in there about filling it. Not saying it would be a bad idea, just that it mentions nothing about it.
Live and learn, I guess.

 

[shdw2001h]

Re: Surging

I had a simular problem with my volvo. I took a gas can,with fresh gas ran the engine on that too see if it cleared the surging, and it did, next I checked the gas tank and found that I had water in the tank, so i pumped out all the water from the lowest point until i got just gas. i also checked the anti-siphon valve on the thank were the hose from the engine connects, found out it was sticking from the water that went through it, so i replaced that. I checked the screen on the bottom of the suction tube that goes in to the tank and found that was dirty. when I removed the the tube that is how i
siphoned the water out. I think the main problem was the anti-siphon valve was sticking. once i did all this the surging when away. one more thing I would check the fuel hoses and see if the inside of the hose are not falling apart or collapsing. I hope this helps.

 

[Fun Times]

Re: Surging

Replaced the spin-on filter with a new one. Parts guy thought I might have another filter, but I can't find the round in-line one he thought it might have. Maybe I only have one? Hope so, because the other one was 5 times more money!

On a side note, I also installed my Smart Tabs. Can't wait to try them out!

Because you have an alpha engine/drive set up, you only have the one fuel filter.

Engine serial number 0M648967 Model number 444106LRS 1998M MERCRUISER 350 MPI ALPHA DRAIN 350 MAG ALPHA MPI

Here are the parts to your engine by going off of your engine serial number.
http://www.mercruiserparts.com/selectDocs.asp?doc_nbr=884717

 

[havasuboatman]

Re: Surging

I knew there was a reason I didn't fill the filter first! I read the FSM! Nothing in there about filling it. Not saying it would be a bad idea, just that it mentions nothing about it.
Live and learn, I guess.

Just the advice from a guy who does this stuff for a living, I learned it from a guy named Jim Fry. He wrote your factory service manual, by the way.

 

[Fun Times]

Re: Surging

Just the advice from a guy who does this stuff for a living, I learned it from a guy named Jim Fry. He wrote your factory service manual, by the way.

Jim is a good guy.

Love his stories.

 

[havasuboatman]

Re: Surging

Jim is a good guy.

Love his stories.

Can he tell a story or what? And as far as he's concerned, O/B motors go on boats. Everything else belongs in a car. This from a Merc. instructor.

 

[Yellow Yota]

Re: Surging

Well, hope to get word tomorrow on what the problem is. Got tired of messing around with it, so I broke down and took it to a shop. Better and more important things in my life right now than working on the boat. So, until that changes, I'll do only the simple things that don't require too much leg work or trial and error.

Thanks for all the input!

 

[Yellow Yota]

Re: Surging

Well, got it back home today. Dropped by the boat shop on my way home from work to check on progress. They had everything back together, but hadn't done a lake test yet. I asked them if everything appeared to be okie dokie, and they said yes. No more codes and it ran good on the hose. I opted to take it home and I'll lake test it myself tonight or tomorrow and save $90 more in labor for their time to take it out for a spin.

If everything is good, it means that the TPS was faulty. When they had it hooked up to the 'puter, it was the only code being thrown. Non consistent voltage through the TPS. Everything else checked out.

Fingers crossed! Hope it runs great again!