Proper Engine and Tune Up Specs Requested

[amajamar]

After reading through the Manual 24 tune up specs (thank you Fun Times for the link) I notice that the Horizon variant of the MIE MAG 350 Gen+ is not specifically listed. My engine's, SN-OL677287, Merc parts breakdown shows a platinum spark plug (superseded to iridium), however since it isn't listed in Manual 24, I am not sure of the plug gap. That said, where can I get the proper (complete) tune up spec printout for my engines? (I suppose it's possible that the spark plug spec is the only difference...)

Thanks in advance!

 

[alldodge]

Re: Proper Engine and Tune Up Specs Requested

After reading through the Manual 24 tune up specs (thank you Fun Times for the link) I notice that the Horizon variant of the MIE MAG 350 Gen+ is not specifically listed. My engine's, SN-OL677287, Merc parts breakdown shows a platinum spark plug (superseded to iridium), however since it isn't listed in Manual 24, I am not sure of the plug gap. That said, where can I get the proper (complete) tune up spec printout for my engines? (I suppose it's possible that the spark plug spec is the only difference...)

Thanks in advance!

On page 1B-9 are inboard engines, which includes your Horizon. The MIE stands for Marine inboard engine. Use specs lined out for the MIE 350 MAG MPI

 

[amajamar]

Re: Proper Engine and Tune Up Specs Requested

On page 1B-9 are inboard engines, which includes your Horizon. The MIE stands for Marine inboard engine. Use specs lined out for the MIE 350 MAG MPI

I see that, however, it does not have a platinum spark plug spec, which the Mercruiser parts breakdown calls for. That's what leads me to ask about the complete and accurate tune up spec for that engine.

 

[Bondo]

Re: Proper Engine and Tune Up Specs Requested

I see that, however, it does not have a platinum spark plug spec, which the Mercruiser parts breakdown calls for. That's what leads me to ask about the complete and accurate tune up spec for that engine.

Ayuh,.... Welcome Aboard,.... Generally speakin', those coated spark plugs are run as gapped, from the box,...

If ya regap 'em, it scratches the coatin', 'n ya got plain ole spark plugs again,...

Which is why I recommend runnin' the ole style MR43T, or MR43TLS, which ever fits yer application,...

 

[amajamar]

Re: Proper Engine and Tune Up Specs Requested

Ayuh,.... Welcome Aboard,.... Generally speakin', those coated spark plugs are run as gapped, from the box,...

If ya regap 'em, it scratches the coatin', 'n ya got plain ole spark plugs again,...

Which is why I recommend runnin' the ole style MR43T, or MR43TLS, which ever fits yer application,...

Hmm, wish I knew that before I bought them... Oh well, it's only money. So, the irridiums come pregapped and that is the correct gap for the engine??

 

[alldodge]

Re: Proper Engine and Tune Up Specs Requested

Hmm, wish I knew that before I bought them... Oh well, it's only money. So, the irridiums come pregapped and that is the correct gap for the engine??

I think (means I'm guessing) they should be pregaped. Put your gap gauge in and find out. As Bondo mentioned, so long as you don't try to regap they will be fine.

 

[amajamar]

Re: Proper Engine and Tune Up Specs Requested

I think (means I'm guessing) they should be pregaped. Put your gap gauge in and find out. As Bondo mentioned, so long as you don't try to regap they will be fine.

Well, that was my original point. What is the correct gap for that plug in that application?

 

[alldodge]

Re: Proper Engine and Tune Up Specs Requested

Well, that was my original point. What is the correct gap for that plug in that application?

Manual shows .045

 

[Bt Doctur]

Re: Proper Engine and Tune Up Specs Requested

But the regular plugs work just fine,and cheaper too. Thinking the newer plugs were just for automotive emissions and just carried over to marine engines.

 

[JustJason]

Re: Proper Engine and Tune Up Specs Requested

So, the irridiums come pregapped and that is the correct gap for the engine??

Correct. Bring your feeler gauge to the auto parts store and make sure they are gapped correctly before you buy them. If they are not, have the parts tard bring out all his plugs until you find 8 good ones.

Thinking the newer plugs were just for automotive emissions and just carried over to marine engines.

Not really emissions. It's more so to cut down on maintaining the engine. Spark plugs are a wear and tear item, they do wear out. The electrodes burn and pit and the gap enlarges on it's own from the electrode material vaporizing over the course of tens of thousands of miles. Once the gap gets to big the coil can not overcome the extra resistance, and it starts misfiring. Not only does the engine run like crap but it is a good way to prematurely burn out ignition coils as well. Plugs with exotic materials (platinum and iridium) do not pit and burn in the same way as a regular plug. And because of that the gaps do not increase on their own. And they can last a lot longer.

Personally, and this is just MHO, regular plugs are fine. Cars engines run lean, and do not load up with carbon internally any more like they used to. Marine engines run rich, and they still load up with carbon. Because of that, what I find is spark plugs in marine engines carbon foul long before the electrode portion of it is burnt out. And you can carbon foul any plug, it's not like iridium plugs are resistant to carbon fouling.

 

[Fun Times]

Re: Proper Engine and Tune Up Specs Requested

Manual shows .045

+1! Your horizon engine model calls for a different plug number then the Mag MPI but the gap remained the same on your engine model. Some of the newer engine models went to .60 so you have to be careful with that. There should be a sticker on top of your engine with the gap setting on it. If so, that is also typically considered one of the best sources for correct information.

This horizon engine calls for an one plug hotter number then the Mag engine. NGK plug #5 is hotter than a #6.

350 Mag. MPI Horizon (Gen+) 350/ V-8 Mercury -HEI 2000 - 2001 0L604000-0M299999 891895A01 N/A 805570A 2 847701Q24 803990 .045

To gap the new type of plugs correctly, you may want to watch the video by NGK. NGK Spark Plugs - Tech Videos

I located a really good Mercruiser gapping guide we all may want to use with these type of questions to help take some of the guess work out of it.
IGNITION ECM COIL WIRES & SPARK PLUG CHART at MarinePowerService.com