2008 Optimax 150, Service Bulletin 2009-026?????

[flashman252]

I have bought a brand new boat to me with a 2008 150 hp optimax. The boat has not been touched from the factory in regards to setup. The old man I bought it from had the original tires on the trailer still and the motor only had 105 hours on it. So I bought the boat (still in immaculate shape) and the motor checked out when connected to the computer. First time out, I was way over propped and had a feeling that would be the case due to our elevation. Only was able to get it on plane 3 times and only saw 4800 rpm. Put a smaller pitched prop on and today it did much better on hole shot but only seeing 4900 rpm. 4 pitch sizes smaller and only gained 100 rpm, so I know this isn't right. Also, at idle it wants to die and I did verify that the hot foot throttle cable is hitting the stop bolt for idle and for WOT. The seals on the screws are still intact what looks like from the factory. But the RPMS die down to about 500 and the rev back up to around 700 causing a vibration and rough idle. So got to cruising around on here and started reading about faulty coils in this year optimax. Can anyone validate this? Cruising around I found that a misfire in these motors resulted in worsening hole shot (wouldn't know, it did way better today with a smaller pitched prop than the first outing), 4900-5000 RPM (seeing this definitely), 10 mph slower at WOT (wouldn't know, today was the fastest I've been in it but only second time out and fist time was a DISASTER), and rough idle (seeing this as well).

Also, how much are spark plugs and coils for this model of mercury? I read that a spark timer test is the way to figure out if the coils and plugs are working correctly. Even found a pretty cool YouTube video of a guy doing it, downside is I wouldn't know what a correct firing vs an incorrect firing would look like. Coils and plugs look stupid simple to get to and replace, but if I can get new coils from a recall or something, then I won't mind doing that and being without a boat for a little while. Thanks for replies in advance guys.

Serial No. 1B539103

[JOE54]

recall is outdated, around 20 a piece depending on location , becarful with #6

[SilverFox579]

^^^^

How long had it been since engine was last run? Did you get any maintenance history information from the seller?

There is a lot of very helpful info you can trust (unlike most youtube videos) in the 2.5L forum (covers your engine) just below this one - FAQ- COMMONLY ASKED/USED 2.0/2.4/2.5 Liter Topics

[EuropeanAM]

Moved to correct forum for you.

[flashman252]

So when I bought the boat, I got a 9 page report from when it was plugged into the motor. It said no faults. It showed the hours run at certain rpm, it has a LONG list of different numbers and figures shown and most of it is jibberish to me. With that said, most of its life it was run at idle and I know that’s not the best but it can’t from an old man who ran it on a private lake and putted around. When it was last run, no idea. The motor starts right up, it seems like it’s got ok power when throttling up but I’m not getting the full rpm. No indicators or beeping and the water pressure is 9-11 at 4900 rpm. I know a minimum of 12 is what the manual says at wot but I’m still 700-800 rpm short. At $20 a piece, I could replace all coils and do spark plugs at the same time. Is this a bad idea? Also, I’ve seen videos of guys running it at idle with water hooked up and you can disconnect a plug and listen to see if the motor dies down, when you plug it back in, rpm picks back up. That would indicate a working coil. If you unplug the clip and the motor rpm doesn’t idle down, then that is indicating the coil is bad in that cylinder. You can verify this by switching two coils and ensuring it happens again on the switch for that cylinder. Has anyone done this and bypass the need for the spark light test deal? I’m not afraid to do this, coils and spark plugs seem super easy and are right there. Just need a little guidance before I go tearing into it. Again, thanks for the replies guys and if it would help, I can upload pics of the report from when I bought the motor. Again, it shows no faults.

[EuropeanAM]

Sorry bud... coils are not $20 each (not even close)... believe you're talking about the general price range of OEM Spark Plugs there.

"Clip unplug" you mentioned may or may not indicate a bad coil. A bad REED can mimic said symptoms, and a bad wire or spark plug would have the same results.

Spark tester or a timing light clipped to each wire, one at a time while you watch the flashing pattern... a decent "layperson" test for out in the field.

[flashman252]

Europe, would you happen to have part numbers for the plugs and coils? And I will go the spark test route. My girlfriend works at a local Mercury dealer. They are pretty good people and I will probably have them go through it but I just hate taking it to someone when I know I can do it myself and I do like being able to diagnose problems on my own and knowing how to fix things. How I have always been with cars, boats, lawnmowers, etc. I get what you're saying in regards to bad wires, and plugs being bad as well. If I determined there was in issue if unplugging that clip, I would change the coil to a different cylinder and see if symptoms follow into that cylinder to ensure it is the coil. Just like what is done with vehicles. I will start with plugs probably and go from there. If anyone could provide part numbers, that would be great. Thanks guys

[SilverFox579]

I'd start here since you don't know what maintenance has been done or when, note the recommended service interval is annually or 100hrs whichever comes first - Recommended Annual Maintenance or Winterization for Optimax Engines

Spark plugs for your engine are addressed in the linked topic above.

[leonreno]

Spark plug requirements are in the faq at the top of the forum page.

[flashman252]

Lots of good info there in the FAQ and will get through a lot of this stuff and also start using the quickleen and quickcare mix in all my tanks and the quickstore when putting it away fro some time. Found the spark plugs I need, will start there for sure as stated. Could not find coil part numbers though. Another thing I saw browsing around is the water strainer. This looks something I need to probably dig into and take a look at as well. Thanks for the help guys, if anyone could provide coil part numbers, that would be great.

[flashman252]

Ok so found the mercury parts list website and entered in my serial number. I found coil numbers to be 8M0077473. Guessing that is the correct part number if in fact I need to order some. $120-$140 a pop.... ouch

[EuropeanAM]

BTW... you can lookup parts on our website (can even order there) at: www.mercurypartsonline.net

Check the basics... and get the Recommended Annual Maintenance up to date.

[flashman252]

Well holy Sh** Europe, thanks a ton pal. Wish I knew about this before even starting this thread. I wouldn't be asking ridiculous questions. Will have the boat in the shop in the next couple weeks for a full check through. Learned a lot today fellas. Appreciate everything.

[leonreno]

No ridiculous questions here, all good questions, that’s how we all learn here.

[JOE54]

agree

[SilverFox579]

I believe Don was trying suggest you get normal maintenance up to date BEFORE you start throwing parts at it. Spark plugs alone can cause the problems you're experiencing and save you a bucket load of $$ replacing perfectly good coils. The 2.5L Optimax is not prone to coil failute like the 3L.

FWIW, every single coil on my 150 is the same as what the engine left the factory with but I DO religiously change plugs annually (never reach 100hrs a season). Lots of great folks here that can help you with your engine. Always best to start with getting all routine maintenance up to date then move out from there.

[flashman252]

Thanks guys all the information provided has been gold. Ordered spark plugs. Will get those in and then have a mercury mechanic waiting to go through it with me and we will check coils and lots of other things, just have to find time to get it over there and be willing to spend some time with him going through it all. As a nurse working in a pandemic = lots of extra overtime right now. Busy busy busy!

[EuropeanAM]

Don't forget the fuel filter... for some reason, we're seeing a much-higher incidence of restricted/plugged fuel filters this year.

[flashman252]

Now let me just clarify, the fuel filter you are referencing is the red one with the teeth on top? I ordered one with the spark plugs and the tool to help get it out (just in case). The round can on the opposite side of the motor that looks like an oil filter on a car is the oil/water separator? Is my thinking on this correct?

[JOE54]

1b539103 150 only has one fuel filter (spin on oil filter type) like all other optimax engines, doesnt have red castle top filter in vst,