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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15620
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have Volvo 8.1 Gxil-e engines but can only get 3000rpm on

Customer Question

I have Volvo 8.1 Gxil-e engines but can only get 3000rpm on port engine, and 3500 on starboard. Yesterday I had fuel checked, replace filters, checked spark on all cylinders, inspected plugs, and local mechanic performed computer diagnosis and everything checked out ok. What else should be checked! I'm thinking starboard will only get 3500 rpm because port is low on Rpm's and starboard is working harder. Is that plausible?My engines are 2006 models. Also, I was having engine backfire intermittently.
Thanks in advance,
Dave Morrow
Submitted: 1 year ago.
Category: Boat
Expert:  Jason replied 1 year ago.

Hi Dave, my name is ***** ***** I will be helping you today.

How old is the fuel in the tank? Was fuel pressure checked while underway? What kind of history or story is there to this boat, when was the last time the boat made full speed, and the engines full power?

Customer: replied 1 year ago.
Yesterday the service tech checked fuel pressure at dock and everything checked out to spec. They looked at plugs and found one fouled excessively. They changed all plugs , then we took the boat out for run under load. Nothing changed. They did get indications that there could be problems with the coil or fuel module that we possibly are not getting proper voltage , I think. They are trained on these engines but haven't come up with solution yet.
To answer your questions, I made a trip prior to problem, and fuel in tank is only one or two weeks old. The fuel was tested and checked out ok. The first time I took the boat out this year, I had the same problem. I returned to gas dock and had mechanic go back out with me. The boat ran fine so we surmised a piece of dirt passed through filter and everything was ok. After that we took a 300 mile trip with no problems. Two weeks later I field up at home dock and original problem is back. Any advice to give to service tech when he comes back today? I'm not at my home port.
Expert:  Jason replied 1 year ago.

Hi Dave. Was fuel pressure checked at idle, or with the boat at max speed, and the engines at max rpm?

Customer: replied 1 year ago.
The fuel flow was checked while boat was in slip initially, at both idle and higher rpm. I don't recall if they checked fuel flow under load when they had there testing equipment connected when we took the boat out
Expert:  Jason replied 1 year ago.

The only true test is with the boat at max speed, anything else really doesn't matter.

How intermittent is this issue? Does it come and go every other trip?

Customer: replied 1 year ago.
Ok, I will check with tech when I speak with him. This is the only time I've had this problem on a trip.
Expert:  Jason replied 1 year ago.

You mentioned it was backfiring. Could you tell if it was popping in the intake manifold, or out of the exhaust?

Expert:  Jason replied 1 year ago.

Are you still with me?

Customer: replied 1 year ago.
I'm not sure, it sounded like a door slamming in the engine room.
Expert:  Jason replied 1 year ago.

The problem is more than likely going to be either clogged fuel filters. Or bad anti siphon valves. Anti siphon valves are check valves on the fuel tanks outlet where the fuel line connects. They look like hose barbs, but they have spring loaded check valves inside of them. Those check valves both stick, and collect debris, restricting fuel flow to the engine. When that happens the higher the rpms gets, the greater the fuel restriction, and the engine ends up starving for fuel. The fuel starvation would also cause popping in the intake manifold. Does that all make sense? If yes, did you have any further questions on the issue?

Expert:  Jason replied 1 year ago.

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the start and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you

Customer: replied 1 year ago.
I will
give you a rating after boat is repaired and I know what was really wrong. I will pass on your reccomendations to service tech
Expert:  Jason replied 1 year ago.

You are most welcome Dave. Good luck!


Expert:  Jason replied 1 year ago.
Hi Dave. Just checking in. Any progress?

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