Engine won't idle

[Searaybio270]

So, here's the story...........

In June I started both engines while still on the land. No problems with either one. A few days later I launch the boat. Starboard engine starts and purrs like a kitten. very happy. Port engine having trouble starting. Finally starts but it is very erradic. After a while it does settle down and I slowly move her to the slip.
Run it for a while in the slip and she appears to be settling down. So I shut both down. Do some work and then head off to help the others at the marina for clean up day. Later in the day I come back and "Hydro Lock". A week later on one engine I am off to see the mechanic at the marina up the river.
They do some tests and find that the engine is in bad shape. I say how since I just had it rebuilt two years ago. They pull the engine and off to the shop for a rebuild.
Now some 8 weeks later the engine is back together. They tell me that at 1500 and 1800 and 2500 RPMs she is spot on. The issue is when she comes down to idle - it surges back up and then back down.
They have checked the IAC, MAF, mechanical fuel pump and the other one, some sensors and sprayed it to see if maybe there is a vaccum leak. I do believe the Mercruiser rep will be there but in the meantime - Any Ideas.
Haven't boated yet this summer and I will spend more money on another engine then I care.
:smt100

 

[2000SR380]

This sounds like a fuel supply problem to me. Before they get all excited and pull the engine again, see of you can swap the fuel supply from the starboard engine. If you had water in the Port side separator, or a malfunctioning fuel pressure regulator, you could have very similar symptoms. When an engine goes lean, sometimes the RPMs will increase for a second or two before the fuel runs out. I think when you drop to idle the fuel supply is shutting off, and then recovering and that what is causing the "surge back up", and then idling back down as the system catches up. My question is what was the original cause of the "Hydro Lock"?? That term usually refers to attempting to compress water in the combustion chambers, and indicates that water was somehow getting into the cylinders. That should not happen. If the engine("dead guy")was originally killed by Hydro Lock the cause of the water leaking into the engine ("shooter") may still be a player.

 

[Searaybio270]

Thanks for the reply. they are swapping parts today. I hope to have it back before labor day. Water was caused from the riser/exhaust manifolds. How I don't know they aren't that old. The boat ran great last season once I got the Starboard engine fixed.

 

[2000SR380]

I will keep my fingers crossed for you. Hope it is something simple!

 

[Searaybio270]

So, Friday afternoon I stop by the marina and they tell me the IAC wasn't working so they replaced it and she ran fine. they also said they would clean her up and I could take it on Sat afternoon or Sunday. I opted for Sunday b/c of the high tide.
On Sunday I go to the marina to find they hadn't cleaned the boat. So I take the next 5 hours and clean the cockpit area and I mean wall to wall. Then the stuff they through into the cabin had to be removed, cleaned or thrown away. Redid all the glass in and out, cleaned the stern and the bow of the boat.
So, now I am pretty close to leaving and start the engines. The port (new engine) is idling around 1500RPMs but after a few minutes settles down to 700/800 and sounds great. Start the Starboard and she goes right into a perfect idle. So I go and undo the power cords and then the lines and pull away.
I am not even out of this very small marina and the port engine starts surging and won't stop. Back to the slip it goes and still no boat. Waiting on a call from the marina to let me know if they figured it out. I am so disappointed. Nine weeks in the shop and still not working. :smt089

 

[Searaybio270]

FollowUp and Hellp ~
So, as of this date the engine still won't idle once it warms up. The have put the computer on it and there are no faults. None. Nada. Nothing. They have replaced parts they thought might be doing it but nothing. They called the regional Mercruiser Rep but he is in Washington State on vacation. I hope he gets back ok as he must be the only contact they have. What is up with that?
So I call Mercruiser place in Wisconsin. They ask if they did a fuel pressure test. Yes they did. All ok. Ignition componets are good. Yes. IAC and MAF all good. Fuel Pump is good. No vaccum issues. Nothing.

Ok guys - Please give me some ideas.

 

[2000SR380]

So, as of this date the engine still won't idle once it warms up. So I call Mercruiser place in Wisconsin. They ask if they did a fuel pressure test. Yes they did. All ok. Ignition componets are good. Yes. IAC and MAF all good. Fuel Pump is good. No vaccum issues. Nothing.

Fuel pressure test does not always tell the whole story. I agree they are on the correct track, but a pressure test will not always show contaminated fuel, or a fuel restriction. For instance if the pump was supplying adequate pressure but pushing through a very small opening, you could get excellent pressure readings, but everything would fall apart as soon as there was a demand for more volume. It is possible you have a secondary ignition issue, but if I was in your shoes I would get a big gas can and set up a known good fuel supply. Then I would purge the fuel system and run the RPMS up under load. A "surging" engine is typically having a fuel supply (or air supply) issue. Assuming that if there was a rag in the intake they would have found it, or you would have seen it, I am putting my money on fuel supply. You could try disconnecting the fuel line and running fuel into a jar while cranking (to check if the volume of fuel moving in each engine is the same). My suspect would be a fuel restriction. If I did that and confirmed good fuel and good volume, but still had failure, I would look at the oil pressure switch, and possibly the temp gage (Funky readings on these gages can sometimes put the engine in Limp-home mode, so a loose or faulty connection could be causing "surging" as the boat moves around more under way).

 

[Searaybio270]

I did get the boat back on Saturday after spending another 3hours cleaning her and asking the marina about the 3ft long scratch in the side of my boat. I am not very happy about the scratch along with the now 8 plus hours of cleaning the cockpit area, swim platform and so on.
As for the boat. They took the wiring harness off and said something about the ends may have been frayed from taking the harness off and back on again. Not my issue. I think they didn't have it on correctly to begin with.
I don't have an issue with the idle anymore. What I do have is between 900 and 1100RPM's I have an oscillating whirring noise. That noise goes up and down and is very noticable by the ear.
We ran the boat at 3300rpms doing about 23MPH for about 20 miles. For those of you in the Bay area, that's from the Bush river to Still Pond and back. We did stop/crawl for a while due to the area we were in. Overall she ran very good.
Now to go pay the rest of the bill and get my warranty info.

 

[Saverio]

Im glad its working out....

do you have any pictures of the engine removal and the bilge?

Saverio

 

[Searaybio270]

I don't have any pictures of the engine or bilge area. Wish I had taken some.
Do you boat out of LI and live there or do you live someplace else. I was born in White Plains, Westchester County. Grew up in Delaware County and now live in Maryland. My brother lives in Mamaroneck, NY. I love going up for the food. Either in the Bronx or at his house.

Im glad its working out....

do you have any pictures of the engine removal and the bilge?

Saverio

 

[Saverio]

I live in Commack LI. But I do all my boating on the southshore in Lindenhurst like the beaches and places to go better.

 

[Searaybio270]

With a little luck I want to go from here to NY by boat. What I spent this year in engine work I could have come there for three weeks or better

 

[Saverio]

wow you might need diesels for that. I saw a 41 for sale by me with twin Cats for 24k just needs a little body work post sandy repair lol

 

[rcknecht]

Joe, You can stop over night at my place on your way to NY... With all the lack of use for your boat this season you should have a lot boat dollars left for gas...This is the best time for boating... It is less crowded the water is warm, and weather is nice....

 

[Searaybio270]

Joe, You can stop over night at my place on your way to NY... With all the lack of use for your boat this season you should have a lot boat dollars left for gas...This is the best time for boating... It is less crowded the water is warm, and weather is nice....

That would be awesome but for sure not this year. Our contract is over with at the end of the month. Right now I am sending resumes like they are going out of style. If it weren't for my contract then in early Nov I am going in for surgery to replace my shoulder. So my season is over.
Now I did go to Fairlee Creek on Sunday afternoon with two marina buddies for a couple of hours. Boat ran good except for the Port engine was fine and now the Starboard is running around 1100RPMs at idle. what is interesting - after we got there and I shut the engines down for while we were there. We restarted when we were getting ready to leave and both engines were spot on.

But if I ever do run north I am stopping by as some of the people I work with go to that area.