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Thanks, we have a maxum 3700 and one of the engines started…

Customer Question
Thanks , we have...

Thanks , we have a maxum 3700 and one of the engines started running rough at idle and would auto shut of. it only runs (rough) now at higher throttle settings

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

We had the injectors cleaned and changed the spark plu leads. spark plugs are quite new ....

Mechanic's Assistant: Is there anything else the Marine Mechanic should be aware of?

Thats basically it ....

Submitted: 10 months ago.Category: Boat
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Answered in 4 hours by:
9/23/2017
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago
Jason
Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 18,165
Experience: Degree in Marine Technology. Gas and diesel marine mechanic.
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Good morning my name is ***** ***** am I speaking with? I read what you wrote but I do not see any kind of model information. Which engine are you asking about specifically?

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Customer reply replied 10 months ago
Hi Jason, This is Fonz, nice to meet you. The engine is a Mercruiser 8.1 HO, petrol engine
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

Hi Fonz. Do you have compression gauge, fuel pressure gauge, and a timing light so you can check compression fuel pressure and spark output?

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Customer reply replied 10 months ago
its all done ... compression is OK, timing OK, fuel pressure OK , spark output not sure but the plugs are new and the leads just changed now too .... seems it IS an ignition issue though. Fuel seems to get into the engine alrighht
Customer reply replied 10 months ago
the engine was running perfect but after a 1 hour run at 2500 RPM, it cut out when idling. Now it just starts with throttle a little open and clearly runs on 6 or 7 cylinders only. Injectors are cleaned
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

The next step is hooking up a scan tool. Do you have Diacom or any other scan tool that will work with this engine?

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Customer reply replied 10 months ago
teh scantool was connected 4 days ago ... all looked good, 631 hours on the engine, just a few sensors that need to be replaced. (camshaft, pitot) , further no abnormalities
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

Are you working on this engine yourself or is somebody else working on it for you?

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Customer reply replied 10 months ago
both ... we have an engineer, but i work on it myself too. at the moment were just doing a trial and error project , but and input from you might be very useful
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

Which scan tool are you using specifically?

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Customer reply replied 10 months ago
it was not mine but i believe a diacom
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

I have diacom as well. Can you do a live data recording with the diacom and send me a recording file?

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Customer reply replied 10 months ago
hmm that will be a bit difficult. It was Al Boom Marine that did the investigation and they charge BIG money for a survey :-)
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

Okay so I dont' understand what we are doing. What kinds of questions did you have for me exactly?

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Customer reply replied 10 months ago
moreover its 21:30 here ... were in Oman :-)
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

Okay so I don't understand what we are doing. What kinds of questions did you have for me exactly?

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Customer reply replied 10 months ago
I was asking for some suggestions as to what the cause might be ,.... but if i its too open for you as far as my details are concerned i guess we will have to continue the trial and error policy
Customer reply replied 10 months ago
thank you for your input .. unfortunately I have to go now but if you have any useful suggestions id be glad . Have a good evening
Marine Mechanic: Jason, Marine Mechanic replied 10 months ago

T​he suggestions are limitless. You literally have the most complicated gasoline engine that Mercury makes. I would need exact numbers and figures, as well as a copy of a live data recording to be of any help.

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