2008 115 4stroke Idle rpm

chili1

Recruit
Joined
Aug 24, 2008
Messages
5
I just replaced 81 115 2stroke with 4 stroke. Had to downsize 20p HiFive to 17p Trophy Plus. This on a 17" Boston Whaler Outrage. So far so good.

But .... this 115 4 stroke Idles at 850 rpm where the 115 2 stroke idled at 600 rpm. My fish troll speed now is close to 3mph (gps) and is too fast.

Merc dealer says the 850 rpm idle speed is fixed and cannot be lowered/reduced at all or to 600rpm. Is this true or false?

Is there any trick to accomplish this? Rumor has it that it can be done.

Thanks....Chili
 

chili1

Recruit
Joined
Aug 24, 2008
Messages
5
Re: 2008 115 4stroke Idle rpm

.....a pail, .....already doing that. ....and wishing I had my 115 2 stroke back.

Along with the high idle rpms, the low rpm throttle control is just not for fishers. Just touching the throttle up gets you 1100 or 1200 rpm. Getting 850rpm to go to 900 and 1000rpm is just a minute touch to the throttle. It takes 4 or 5 tries from idle to get 1000 rpms. Not at all convenient. :mad:

I'm just kinda ticked with Merc. Nowhere in theirs promos or engine specs do they spec the 850 rpm idle. Also ticked with the Merc dealer who knew I was a fisher and sold me the boat and 2 stroke originally. Let me tell you, a 115 4 stroke on a 17 or 18 footer will no be a fish troller without a pail or trolling plate gizzmo. :mad:

But there is some good news. The 115 2 stroke was 17 years old and still running strong. I took it off for a reliability factor as I fish off shore in the Pacific. This motor had 2926 hours on the meter and cost me spark plugs and a thermostat total. I think that could be merc record. :)

.... Chili
 

Kev144

Petty Officer 2nd Class
Joined
Oct 16, 2007
Messages
159
Re: 2008 115 4stroke Idle rpm

.....a pail, .....already doing that. ....and wishing I had my 115 2 stroke back.

Along with the high idle rpms, the low rpm throttle control is just not for fishers. Just touching the throttle up gets you 1100 or 1200 rpm. Getting 850rpm to go to 900 and 1000rpm is just a minute touch to the throttle. It takes 4 or 5 tries from idle to get 1000 rpms. Not at all convenient. :mad:

I'm just kinda ticked with Merc. Nowhere in theirs promos or engine specs do they spec the 850 rpm idle. Also ticked with the Merc dealer who knew I was a fisher and sold me the boat and 2 stroke originally. Let me tell you, a 115 4 stroke on a 17 or 18 footer will no be a fish troller without a pail or trolling plate gizzmo. :mad:

But there is some good news. The 115 2 stroke was 17 years old and still running strong. I took it off for a reliability factor as I fish off shore in the Pacific. This motor had 2926 hours on the meter and cost me spark plugs and a thermostat total. I think that could be merc record. :)

.... Chili


Dont know the records but we just had a guy come into our marina for a stator on a 86 150 with 4003 hours on it. Still in great condition and holds 130 psi across all cyl.
 

Irv964

Petty Officer 1st Class
Joined
May 3, 2008
Messages
315
Re: 2008 115 4stroke Idle rpm

Dont know the records but we just had a guy come into our marina for a stator on a 86 150 with 4003 hours on it. Still in great condition and holds 130 psi across all cyl.

Those are some great numbers! Any idea what brand of oil(s) they are using?
I am hoping my motor lasts that long (07 Merc 90 4 stroke) but I know more things come into play than just oil.................Irv964
 

octane

Seaman Apprentice
Joined
Apr 5, 2008
Messages
47
Re: 2008 115 4stroke Idle rpm

I have the same engine with the same idle speed. I remember seeing on the mercury web site that the idle speed was electronicaly controled.

trolling is usualy not recommended with a big 4 stroke since some have a tendancy to "make oil" (water condensation in the oil because the oil doesn't get hot enough). There should be some info on this somewhere around here...
 

chili1

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Joined
Aug 24, 2008
Messages
5
Re: 2008 115 4stroke Idle rpm

I have the same engine with the same idle speed. I remember seeing on the mercury web site that the idle speed was electronicaly controled.

trolling is usualy not recommended with a big 4 stroke since some have a tendancy to "make oil" (water condensation in the oil because the oil doesn't get hot enough). There should be some info on this somewhere around here...

That's a new one to me. My understanding of "make oil" is overproping, and not achieving RPMs at WOT and putting excessive gasoline into the oil. These engines have thermostats to maintain operating temps. IMHO, it is hard for water to condense at 190 F degrees.

I found a more technical forum here on Merc 4 stroke 115 idle for those interested:
<http://continuouswave.com/ubb/Forum4/HTML/006133.html>

In this thread, there is reference to the SELOC repair manual for Merc/Yamaha 115 that are good to 2004. This is then for Yammie engines only. My dealer has the Merc Factory manual for 115 but it is for the Yammie engine as well.

Does a Merc factory manual exist for 2007/08 115 with merc made engine?

.... Chili
 

octane

Seaman Apprentice
Joined
Apr 5, 2008
Messages
47
Re: 2008 115 4stroke Idle rpm

That's a new one to me. My understanding of "make oil" is overproping, and not achieving RPMs at WOT and putting excessive gasoline into the oil. These engines have thermostats to maintain operating temps. IMHO, it is hard for water to condense at 190 F degrees.

I found a more technical forum here on Merc 4 stroke 115 idle for those interested:
<http://continuouswave.com/ubb/Forum4/HTML/006133.html>

In this thread, there is reference to the SELOC repair manual for Merc/Yamaha 115 that are good to 2004. This is then for Yammie engines only. My dealer has the Merc Factory manual for 115 but it is for the Yammie engine as well.

Does a Merc factory manual exist for 2007/08 115 with merc made engine?

.... Chili

You are right about the overproping, but if you read here (http://forums.iboats.com/showthread.php?t=158085) is also explains the other causes.

as for the merc factory manual, I bought one directly from merc as there isn't one yet from other companies It's 70$ here (https://appcenter.mercurymarine.com/litreq/) you just need to give them the serial number. I also got the parts catalogue and diagrams for a little extra. there are all very well done!
 

Kev144

Petty Officer 2nd Class
Joined
Oct 16, 2007
Messages
159
Re: 2008 115 4stroke Idle rpm

Those are some great numbers! Any idea what brand of oil(s) they are using?
I am hoping my motor lasts that long (07 Merc 90 4 stroke) but I know more things come into play than just oil.................Irv964

Guy has money, he uses the mercury brand performance semi synthetic blend oil. Peeled his motor apart last year to replace the rings and check (didn't need them, but at the time with 3700 hours, it was time to look) and we replaced the rings, and everything else was in great shape.
 

Irv964

Petty Officer 1st Class
Joined
May 3, 2008
Messages
315
Re: 2008 115 4stroke Idle rpm

Guy has money, he uses the mercury brand performance semi synthetic blend oil. Peeled his motor apart last year to replace the rings and check (didn't need them, but at the time with 3700 hours, it was time to look) and we replaced the rings, and everything else was in great shape.

Good to know, I was considering an aftermarket synthetic but I think I will run the Merc semi now that I read this. Thanks.........Irv964
 

chili1

Recruit
Joined
Aug 24, 2008
Messages
5
Re: 2008 115 4stroke Idle rpm

You are right about the overproping, but if you read here (http://forums.iboats.com/showthread.php?t=158085) is also explains the other causes.

as for the merc factory manual, I bought one directly from merc as there isn't one yet from other companies It's 70$ here (https://appcenter.mercurymarine.com/litreq/) you just need to give them the serial number. I also got the parts catalogue and diagrams for a little extra. there are all very well done!

Thanks for the info Octane. I ordered the Service and Parts Manuals today.

As far as I am concerned, "making oil" by water condensate will make the oil look like skim milk long before you you can see the level rise on the dip stick. Makes me wonder how big an issue this is. One in 10, 1 in 50 or 1 in a thousand.

.... Chili
 

chili1

Recruit
Joined
Aug 24, 2008
Messages
5
Re: 2008 115 4stroke Idle rpm

I just replaced 81 115 2stroke with 4 stroke. Had to downsize 20p HiFive to 17p Trophy Plus. This on a 17" Boston Whaler Outrage. So far so good.

But .... this 115 4 stroke Idles at 850 rpm where the 115 2 stroke idled at 600 rpm. My fish troll speed now is close to 3mph (gps) and is too fast.

Merc dealer says the 850 rpm idle speed is fixed and cannot be lowered/reduced at all or to 600rpm. Is this true or false?

Is there any trick to accomplish this? Rumor has it that it can be done.

Thanks....Chili

Here is my answer to this (my) problem. It turns out that my Idle speed is 738 rpm, The engine spec is 700 rpm +/- 50 rpm....so I am high, and I can't change that. My estimated 17' Whaler Outrage weight, all fish gear with 2 Adults and 18 US Gallons fuel is 2400 Lbs, OK Canada that's 1088Kg.

So, I just bought another prop...a Merc Vengeance 14 pitch (pn 48-17314 A46) I was at 17 pitch and now 14 pitch. Simple math says this prop wud be 82 % of the speed of the 17 Pitch prop. So, here are the results of my test last week.

MERCURY TROPHY PLUS PROPELLER - 17 PITCH

13 3/4" diameter, 4-blades, stainless steel construction
Quicker hole shots, great speed
Dramatically improves handling and reduces steering loads
Applications: Outboards 75 hp and up
Comes equipped with the Flo-Torq II hub kit
Performance Vent System with large vent fittings

Model No. 48-825930A46
-------------------------------------------------------------
MERC VENGEANCE PROP - 14 PITCH
MODEL 4817314A46
Comes with Flo-Torq III hub kit
13 3/8 diameter, 3 blades, stainless

17 to 14 pitch is 82% 2.8 mph shud go to 2.31 mph.

13 3/4 inch diameter to 13 3/8 dia is 3% smaller.

Test done July 8/2009 Trophy versus Vengeance:

................................................ Trophy.............. Vengeance
Idle speed (738 RPM).........2.95 mph .............2.35 mph
Speed at WOT .....................35 mph................35 mph
RPM at WOT........................5000 rpm.............5900 rpm

I do have slight (very temporary) cavitation on full load take off but I can live with that. The good news is I now have my fishing trolling speed and my WOT rpm's are good to the factory spec (5900 t0 6300 rpm)

AMEN...... Chili
 
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