RMP questions 115 Mariner

[j_martin]

Re: RMP questions 115 Mariner

Spark is tested using a spark gap tester in place of the plug. There are versions of them that can test all the sparks at the same time.

Is this one of those engines that idle on 2 cylinders? In that case, the way to get a hole shot is to use a ventilated prop to let it spin up freely at first.

Maybe it's time to get an OEM maintenance manual and read up on the animal. It might be running normally. That manual also has all the preventative and repair maintenance instructions you need.

hope it helps
John

 

[davidf5252]

Re: RMP questions 115 Mariner

I dont know anything about this motor other that a later 80 mariner..

here is the only number that was on the shaft/lu it was stamped on like a serial number with a metal plate...

0A986297 but then i googled that nothing came up.... where can i find the model number of the motor so we all know which one we're talking about???

 

[davidf5252]

Re: RMP questions 115 Mariner

What's the max RPMs for this motor? I didn't see the year or any mention of 2-stroke or 4-stroke (maybe I missed it). If this is the older, late 90's/early 2000's 2-stroke (non-optimax), aren't the RPMs supposed to max out around 5,250? I think there's a sticker on the motor that says what max RPM should be. Might want to check that to see if 5,900 is too high.

I've had my RPM gauge go goofy from time to time and say RPMs are higher than they actually are. Knocking my knuckle on the gauge usually fixes that problem.

Just an idea...

I dont know the max rpms, it is a 2 stroke late 80's?? Mariner 115

I am at work and could ask my baby sitter to take the cowl off bt i dont know if she could handle that.... ill run home and do it real quick

 

[davidf5252]

Re: RMP questions 115 Mariner

Also, the bog-down problem out of the hole sounds consistent with this motor being the 2+2 115, where only the top two cylinders fire until the motor gets to somewhere around 2,000RPM, and then she takes off. Again, if that's the case, there isn't much to be done about that, I don't believe.

Look up 2+2, and you'll find a plethora of information.

In other words, it sounds like your engine might be running normally, save the RPM gauge giving you a potential false reading at 5,900.

How would I know if it it is a 2=2 motor??? late 80s mariner 115 : dunno :

 

[davidf5252]

Re: RMP questions 115 Mariner

Spark is tested using a spark gap tester in place of the plug. There are versions of them that can test all the sparks at the same time.

Is this one of those engines that idle on 2 cylinders? In that case, the way to get a hole shot is to use a ventilated prop to let it spin up freely at first.

Maybe it's time to get an OEM maintenance manual and read up on the animal. It might be running normally. That manual also has all the preventative and repair maintenance instructions you need.

hope it helps
John

OK ill go buy a spark gap tester... and i have no clue if it idles on 2 or all 5.... yeah i need a manual..

 

[j_martin]

Re: RMP questions 115 Mariner

From the Serial Number, here's the parts list.

http://www.usboatsupply.com/Mercury_Mercruiser_Parts_Catalog3a.php?mc=01&ms=6320&si=360

It does have a rev limiter on it, set at 5250. Perhaps that is failing and allowing it to rev from time to time. It may be removable.

If it runs on 2, then picks up 2, the pickup would be in the carburetor linkage. That should be obvious if you watch the carbs while you operate the throttle. (engine off, of course) It should open up and fire on all 4 at blastoff.

This may be as simple as defeating the rev limiter and running premium oil, like pennzoil full synthetic.

A good place to ask questions would be screamandfly.com

hope it helps
John

 

[davidf5252]

Re: RMP questions 115 Mariner

From the Serial Number, here's the parts list.

http://www.usboatsupply.com/Mercury_Mercruiser_Parts_Catalog3a.php?mc=01&ms=6320&si=360

It does have a rev limiter on it, set at 5250. Perhaps that is failing and allowing it to rev from time to time. It may be removable.

If it runs on 2, then picks up 2, the pickup would be in the carburetor linkage. That should be obvious if you watch the carbs while you operate the throttle. (engine off, of course) It should open up and fire on all 4 at blastoff.

This may be as simple as defeating the rev limiter and running premium oil, like pennzoil full synthetic.

A good place to ask questions would be screamandfly.com

hope it helps
John

I went home just now and got some more numbers off the motor and info...

It has six spark plugs and 2 carbs.... 2 stroke...

Serial number 0A986297

there was a round aluminum plug pressed into the side of the head/block?? it said A986297

some barcode on the motor or a part of it M 55504590

 

[davidf5252]

Re: RMP questions 115 Mariner

"From the Serial Number, here's the parts list.

http://www.usboatsupply.com/Mercury_...=63 20&si=360"

that says 4 calendar.... why would it have 6 spark plugs???? any wai to find out what year this thing is??? or how may cylinders...??

 

[davidf5252]

Re: RMP questions 115 Mariner

"It does have a rev limiter on it, set at 5250. Perhaps that is failing and allowing it to rev from time to time. It may be removable."

so maybe the prop came out of the water and was trimmed up to much allowing it to over rev to 6k??

 

[davidf5252]

Re: RMP questions 115 Mariner

I also need some more info or what info do ineed on it so iccan call and get a fule filter and new plugs???

 

[j_martin]

Re: RMP questions 115 Mariner

Now nobody knows what you have.

A 6 cylinder engine has 3 carbs on it. One with that serial would be a V6., the carbs would be 2 barrell.

You said it is a 115 hp engine. That would be a 4 cylinder engine, 2 carbs, 4 plugs.

2 ways to go.
1. The serial number should be trackable directly to the engine build drawing set by a merc dealer. It used to be available at mercurypartsexpress.com, but they took it down and substituted an inferior system.

2. You could take some pictures and post them. Covers off and a couple of angles would help.

To post pictures, it's best to either take them at 640 x 480 resolution, or edit the pictures, changing the size to that, then save them in Jpeg (*.jpg) format. that way they will have decent detail and be under 100 kb so the forum will accept them. Upload them using the manage attachments button.

hope it helps
John

 

[davidf5252]

Re: RMP questions 115 Mariner

Now nobody knows what you have.

A 6 cylinder engine has 3 carbs on it. One with that serial would be a V6., the carbs would be 2 barrell.

You said it is a 115 hp engine. That would be a 4 cylinder engine, 2 carbs, 4 plugs.

2 ways to go.
1. The serial number should be trackable directly to the engine build drawing set by a merc dealer. It used to be available at mercurypartsexpress.com, but they took it down and substituted an inferior system.

2. You could take some pictures and post them. Covers off and a couple of angles would help.

To post pictures, it's best to either take them at 640 x 480 resolution, or edit the pictures, changing the size to that, then save them in Jpeg (*.jpg) format. that way they will have decent detail and be under 100 kb so the forum will accept them. Upload them using the manage attachments button.

hope it helps
John

it has 6 plugs and i saw 2 carbs...i looked at te otro for less than 1 minute and ran back to work.... it probably has a 3rd carb maybe i didnt see it...

So if it is a 6 cyl and has 3 carbs...can i get a link r specifics on this motor?

Does the serial number match to a 6 cyl or 4? it CANT be a 4 cyl die to 6 plugs...

THANKS!!

 

[davidf5252]

Re: RMP questions 115 Mariner

"You said it is a 115 hp engine. That would be a 4 cylinder engine, 2 carbs, 4 plugs." so it could have the wrong COWL on it?

it says mariner 115

only pic i have at work..

 

[davidf5252]

Re: RMP questions 115 Mariner

OK there are 3 carbs and 6 plugs...so what year, model and specs, may RPMS? is this thing???

THANKS

 

[j_martin]

Re: RMP questions 115 Mariner

That's an inline6? 3 single barrel carbs. early 80's, 115 at the prop, would be a 100 by modern standards. Should spin up to high 5G's nicely.

Didn't know they went that high in serial number.

John

 

[davidf5252]

Re: RMP questions 115 Mariner

That's an inline6? 3 single barrel carbs. early 80's, 115 at the prop, would be a 100 by modern standards. Should spin up to high 5G's nicely.

Didn't know they went that high in serial number.

John

Ye s 3 single barrel carbs...

ok but there is no way to tell by that SN exatly what year it is and specs on the motor???

again im not getting high 5's im getting 5200 98% of the time...

Any one i could call and give that SN to that could tell me some specs?

you have been a huge help...

So do you think the prop could be causing the bogg on low mid rang?? or do i still ned to run seafoam though it and change plugs? how can i find out what plugs in need a fuel filter???

 

[j_martin]

Re: RMP questions 115 Mariner

From a table I have, it's a 1986 115 L6, 2.875 bore x 2.546 stroke.
WOT rpm is listed at 5000 - 5500.

As I said before, a mercury dealer should be able to cross the serial number to a parts list, theoretically without a description of the motor.

It would be reasonable to prop it for 5900 rpm. That prop should spin up like that on that 2:1 ratio LU.

A plug misfire would cost about 800 - 1000 RPM at WOT. If the plugs aren't fresh, that would be the first place to look. Plugs are a maintenance item.

Fuel is "filtered" by an inlet screen on the fuel pump.

here's the parts lookup for it.
http://www.usboatsupply.com/Mercury_Mercruiser_Parts_Catalog3a.php?mc=01&ms=6250&si=683

Hope it helps
John

 

[davidf5252]

Re: RMP questions 115 Mariner

Thanks!!!

I am on hold with a marina and described what was going on what RPMs it is turning and i toldhim what prop i had...

he said that 20P prop will make it bogg out of the hole and lose RPMs on the top end he said i should drop down to an 18P is he yanking my chain to make a sale?

 

[davidf5252]

Re: RMP questions 115 Mariner

"WOT rpm is listed at 5000 - 5500."

so it is within normal range....

 

[j_martin]

Re: RMP questions 115 Mariner

"WOT rpm is listed at 5000 - 5500."

so it is within normal range....

That's right. Do you have a GPS reading for how fast you go at 5200 rpm?

Concensus is that it would rather spin too fast than too slow.

John