Mercury Mag 350 loses power

[GAH111]

I have a 2008 220 I've owned for 3 years, with less than 400 hours. When at operating temperature it will intermittently lose power, rpm and speed will decrease. It does not seem to be missing but difficult to tell. I was going to do plugs, cap, fuel filter, etc. just because its time. It would seem I've got a coil issue but I would like some input. My mechanical skills are described as such: If there's a YouTube video I can fix it, which means I'm not really good at diagnostics.

Please let me know what you all think. I'm really surprised there isn't an OBD II port.

G.H.

[Big Block Power]

There is a diag. Port but you need a merc tool. Sounds like your ok the correct trail though.

[SAB220]

G.H. -If your comfortable with doing a tuneup, and its time then then do it. Please make sure you use OEM Mercruiser parts only (oil, fuel/gas filters, cap, wires, NGK plugs). However, I don't think the tuneup your problem but the mechanic might want to do a tuneup first before diagnosing the engine therefore you can save a few bucks. I would bet its a sensor like crank-shaft position sensor, or a fuel pump or the ECM. Engine appears to being starved of fuel. Why? Fuel rail pressure? Look on top of the engine for the OBD II port. Good all engine port reader with adapters >$800.

[bruceb58]

His engine will not have an OBD 2 port. He would need to buy a scanner with the appropriate adapter like a Rinda. I own the Rinda Diacom.

I do agree that the first thing I would do is replace the cap, rotor, spark plugs and fuel filter. I would then measure fuel pressure.

[SAB220]

Bruce - My 2004 220 350 mag scan port is siting on top of the engine. As a member of a marine engine forum, your Rinda scan tool has been recommend by the forum marine mechanics as the best scan tool. For me the question now becomes do you go out and spend good money on the best scan tool in the market (plus training) for one or two engines when your going to have the work done my a marine mechanic anyways? In addition you may need additional tooling to diagnose the problem in that Rinda engine system.

[bruceb58]

Bruce - My 2004 220 350 mag scan port is siting on top of the engine. As a member of a marine engine forum, your Rinda scan tool has been recommend by the forum marine mechanics as the best scan tool. For me the question now becomes do you go out and spend good money on the best scan tool in the market (plus training) for one or two engines when your going to have the work done my a marine mechanic anyways? In addition you may need additional tooling to diagnose the problem in that Rinda engine system.

It's not an OBD2 connector its a proprietary connector.

I am on my second Rinda. The first was just a Rinda techmate. It paid for itself in just one instance when I was able to solve an over cooling issue with an outboard motor. I have the Rinda ahead of time to diagnose an issue I may have in the future. I keep my Cobalt in the water in Lake Tahoe. If I can prevent myself from pulling the boat, driving it 2 hours to the closest dealer, letting it sit for a month while they can get to it, and ten tow it 2 hours back, it pays for itself in a heartbeat. In a previous life(now retired) I was an EE for an automotive electronics division of one of the big 3. I worked with engine ECUs. I know the value of proper diagnostic equipment. For my vehicles, I use an https://www.autoenginuity.com/?gclid=EA ... gLuyPD_BwE scanner. I can't even count how many times it has helped me diagnose issues with my vehicles.

Please explain what a "Rinda engine system" is.

Out of curiosity, which marine engine forum are you on?

[dustinm]

Bruce - My 2004 220 350 mag scan port is siting on top of the engine. As a member of a marine engine forum, your Rinda scan tool has been recommend by the forum marine mechanics as the best scan tool. For me the question now becomes do you go out and spend good money on the best scan tool in the market (plus training) for one or two engines when your going to have the work done my a marine mechanic anyways? In addition you may need additional tooling to diagnose the problem in that Rinda engine system.

If your going to have a marina fix the boat (as in only one boat, your boat) anyway I dont see a reason to buy one. Now if you were a mechanic yourself and planned on fixing your boat plus all of your buddies I could see the value. Lets face it, it should take less than an hour to diagnose with a scan tool, how many times would it take to pay for this scanner for one boat? Plus if you bring the boat it "diagnosed" I guaranty if you are wrong the boat will sit there twice as long and with a larger final repair ticket than if you just had them do everything. This is all considering you have a competent honest mechanic/marina.

[SAB220]

Bruce - The Rinda engine system is, and I'm making an assumption, that you need additional tools to diagnose that boat system that Rinda scanner points to, e.g. compression test, coolant pressure tester, multimeter, leak down leak down kit, schrader valve tool/gauge, OEM tool, etc, etc. You may have the tool in your tool box but this backyard mechanic may not. The forum is of the same name: marine engine forum.

Dustin - that's the issue I only have one boat, however, I have 3 other Powersports in addition to the boat. If I could find a scan tool that fits Mercruiser, Polaris, and Yamaha please let me know. In order to use/find a competent honest marine mechanic I leave these high priced lakes and trailer the boat to the coast.

[bruceb58]

Bruce - The Rinda engine system is, and I'm making an assumption, that you need additional tools to diagnose that boat system that Rinda scanner points to, e.g. compression test, coolant pressure tester, multimeter, leak down leak down kit, schrader valve tool/gauge, OEM tool, etc, etc. You may have the tool in your tool box but this backyard mechanic may not. The forum is of the same name: marine engine forum.

Yes...I own all the tools I would need to diagnose what the Rinda scanner would point me to look at.

I am not saying every person needs to own a scanner. I was replying to your suggestion he needs an OBD2 scanner which will not work on a marine engine as you were suggesting in the first place. Marine engines can't be scanned with an OBD2 scanner...they aren't the same protocols. Most people on this forum likely don't even do their own maintenance let alone able to debug electronics on a modern engine.

A scanner is just a tool...like a multimeter, compression tester...if you don't know how to use the tool, it's not going to do you much good.

Look on top of the engine for the OBD II port. Good all engine port reader with adapters >$800.

[GAH111]

I'll do the plugs, wires, etc., as you say it's time. The boat is 3 hours away so I'm trying to line up all the stuff I need. Since these don't have coil packs like a car where is the coil and should I replace it along with the other components. Any idea what fuel pressure I should expect?

As for scanners I was hoping it would take a standard automotive unit. I use a $30 OBD 11 scanner and Scanmaster app for my cars. Also, the BMW group has free downloads of the INPA software to diagnose BMW and Mini. Since this is my first foray into marine engines I was looking for something I recognized.

Thank you and let me know if you have any tips for getting my oversized body in the engine compartment of my 220.

GAH

[GAH111]

One last thing. If anyone has part numbers for plugs, wires, cap for a 2008 Mag 350 it would speed the process.

[bruceb58]

really doubt it's the coil but it looks like this. Just follow the high tension lead from the distributor to it. Look for a GM Delco EST Voyager coil if you want to buy one.

Can't even count how many coils people replace when not needed.

[GAH111]

Thanks for the info on the coil. I'll replace the fuel filter, plugs etc. and check the fuel pressure.