Help, Starboard engine having low speed issues

[richcam1]

I am new here to the forum. What a great resource!

I have a 2007 280 Sundancer with 2x 4.3L Alpha (EFI) engines. I have an issue that I nor the mechanics have been able to pin down.

Once the engines are hot, lets say after an hour of running, the starboard engine will trip a "TPS" or "Trim" alarm and the engine will drop approximately 500 rpm. It only happens at lower RPMs like 1300 or lower. If I am idling it will stall the engine. Then often ten minutes later the RPMs will pop back up the 500 it lost. It seems to start after we come off plane and it continues.

My thoughts so far after reeding some posts here.

1. IAC valve?
2. TPS Sensor?
3. Salt water VS. wiring harness! (Today my wife drove as I watched the engines with the engine hatch open. We were on plane and she feathered it down to 1200 RPM. I observed water (salt) coming forward from the swim step, through the trunk spillway, through the stern-wall spillway into the engine compartment gutter and spilling on top of the Starboard Engine. It lands on the wiring harness!!!! But, the engine hatch was up.

Any wisdom or thought would be greatly appreciated!

Thank You,
Rich

 

[beachcombersc]

With twins I would swap part from side to side. With a newer year like you have. I would have a sit down with the dealer...

Does it ever smell funny(bad)when it dies??

Mine had a bad connection at the port fuel pump. Black spots on the terminals.

You can get to the connector getting your head almost to the hot water heater. Its dropping down from the top. near the engine mount. Two relays on the top of the engine, one is for the fuel pump. You can test amp loads there quite easily.

Good luck!!!

 

[beachcombersc]

Location????

 

[beachcombersc]

TPS + IAC are both suspects....

 

[richcam1]

I am in SoCal.

 

[richcam1]

With twins I would swap part from side to side.

Good point.

The dealer is on on it, but just hasn't found it...yet. Thats why I am looking in to the issue.

 

[richcam1]

Oh yeah, I have 2x 4.3L Alpha engines with EFI. They are not recording codes on this issue.

Any other thoughts?

 

[richcam1]

It is looking like it was the trim sensors on the stearndrive. We had to pull the boat out of the water to get to them.

Evidently, if the computer thinks the prop is up out of the water it sounds an alarm and puts the engine in a "safe mode" so as to not over-rev with no water resistance on the prop.

I hope this is the fix. We will be taking it out tomorrow on a 30+ mile run. I will know more then.

 

[gerryb]

I think an engine turning 4000 RPMs is not turning at a low-rev level, but I don't know what the rev limit is when in the safe mode. I would have thought it was MUCH lower, less than 2000 for sure.

 

[Tippy Canoe]

I had the identical problem yesterday on my season's first voyage on my port engine. My mechanic believes it is the IAC valve and has had many Mercruisers with this problem. He believes that it is directly related to ethanol gas. On one hand I hope I don't have to pull the boat as she just got splashed 2 days ago but on the other hand, ethanol is not going away any time soon so I don't which would be worse.

KV

 

[flflatrate]

trim sensors will do that 2 you. I think you can go into the sc tach and shut the trim gauge off and try that before pulling the boat out of the water.

 

[richcam1]

Well, it is getting even more complicated!

I have new trim sensors and a new IAC, I also have removed the trim sensors from the smartcraft setup menues.

The problem continues, but less. Any other ideas?

 

[chris41483]

The distributor pickup. I had the same issue with the "twins." It was coincidentally my starbord engine as well. The mechanic told me there was no way that the pickup could do that when I suggested it to him, but I bought one and installed it anyway, I have not had an issue since. All you need is a flat head screwdriver, the part (approx. $60), and 20 minutes of free time. (I have also not been back to that mechanic)

 

[flflatrate]

what motors do you have EFI or MPI. EFI have the distributor sensor that go bad allot. They had a 2 wire one and now they have a 3 wire sensor. the extra 3rd wire is black and goes to ground. if you have a MPI it doesn't have that distributor sensor. Tell me what the exact problem again, and when it happens.

 

[richcam1]

I have a 2007, 2x efi 4.3 alphas

 

[flflatrate]

I would start with what chris said.

 

[beachcombersc]

My mechanic believes it is the IAC valve and has had many Mercruisers with this problem. He believes that it is directly related to ethanol gas.

KV

I think this is a BS excuse. I dont see how they could be related. The steper motors are failing. Its got nothing to do with the Port side of the sensor. I believe Merc shoud but everyone of those bad sensors from us!!!

 

[flflatrate]

your rite beachcombersc. those motors are failing and also the rod inside gets corrodded with salt.

 

[beachcombersc]

your rite beachcombersc. those motors are failing and also the rod inside gets corrodded with salt.

Not sure how salt would get to the rod. Mine is sealed up tight. Only air getting to it is from the intake ports. No salt should be at that point, right?

 

[flflatrate]

I see on some of them if you pull the flame arrestor then pull the iac muffler out with a pair of needle nose I've seen some with salt all over them. Then when pulling the iac motor off I see some of them with almost like a salt spray inside of them. that usually happens if someone had a salt water leak on the motor, then months after they fixed leak the iac starts to stick. Or even with some of the 280 or 290 da's when someone slows down real quick the water will come up to the transom door then go into where the engine hatch sits and those hatches down always seal good and after a while the intake will suck some water in. It only needs a little.