Beyond the factory RPM range...

[jrumon]

Hey guys... I felt this is worth is own thread..

Looking for more speed and running higher RPM???

Keep in mind that that is the factory recommended "CONSERVITIVE" rpm range... mainly so warrentee can be issued and idiots don't blow them up by running wide open all day long. Most stock motors will spin 500 more than stock (as long as its short peroids of time) with no "real" concern but a few things to consider:

#1. Stock motor power bands tend to drop off after the top "recommended" RPM range... so modified motors (reeds, velocity stacks, tuners, relieved exhausts, etc.) can pull more RPM and make more power. We all know that more power and more RPM equals more speed!

#2. Stock oil injection can get a bit scary going high rpm...I don't trust and notice that ALL factory race motors run pre-mix at 40:1 with good oil for a reason. If you plan on running it hard or at higher than stock RPM...loose the injection and pre-mix!

3. Some of the newer motors (mainly EFI) have factory rev limiters built in...you really can't over-rev it!

Given that, I wouldn't be afraid to run past that max recommended RPM a little bit as long as the motor is in good shape... 99% of outboard "blow-ups" are from overheating, oil injection failing, or fuel ratio running too lean...RARELY ever RPM related!!! Jim.

[jrumon]

Hey guys... I felt this is worth is own thread..

Looking for more speed and running higher RPM???

Keep in mind that that is the factory recommended "CONSERVITIVE" rpm range... mainly so warrentee can be issued and idiots don't blow them up by running wide open all day long. Most stock motors will spin 500 more than stock (as long as its short peroids of time) with no "real" concern but a few things to consider:

#1. Stock motor power bands tend to drop off after the top "recommended" RPM range... so modified motors (reeds, velocity stacks, tuners, relieved exhausts, etc.) can pull more RPM and make more power. We all know that more power and more RPM equals more speed!

#2. Stock oil injection can get a bit scary going high rpm...I don't trust and notice that ALL factory race motors run pre-mix at 40:1 with good oil for a reason. If you plan on running it hard or at higher than stock RPM...loose the injection and pre-mix!

3. Some of the newer motors (mainly EFI) have factory rev limiters built in...you really can't over-rev it!

Given that, I wouldn't be afraid to run past that max recommended RPM a little bit as long as the motor is in good shape... 99% of outboard "blow-ups" are from overheating, oil injection failing, or fuel ratio running too lean...RARELY ever RPM related!!! Jim.

[Chris]

I won't run past the red line. Never have never will.

[175checkmate]

Lets see. I have milled heads, velocity stacks, relieved exhaust, tuner, larger carbs. 2.4 fishing motor. The guy that built it builds and races a pro-gas outboard allison. Here is what he told me.
I asked him what rpm to run the motor. His reply. " If you want to rebuild it every year, it will turn 8000rpm. If you want it to live for a few years don't turn it past 7000 rpm. So I am running right at 6400 rpm. Hopefully the bottom work I am doing along with the rest of the stuff I have changed will get me more speed and reving about 6800-7000.

[jrumon]

CHRIS... come on buddy...live a little!!!

Remember that STOCK motors might not benefit from any more rpm (power band flattens out)... but don't be afraid to spin a little past that if it's making more speed!!!

Merc builds their motors on a 20% margin of safety on their rotating assemblies... that means a 6000rpm "max recommended rpm range" can spin as high as 7200rpm with little to no risk of "blowing up" as long as you consider what I mentioned in the start of this thread. http://www.checkmate-boats.com/infopop/emoticons/icon_cool.gif

[jrumon]

175checkmate...
I somewhat agree with your buddy...an I have built several 2.4L's like yours...all of which lived several seasons of 6800+rpm blasts and never a single proble...in fact (10 years later and my buddy still has the boat and still runs awesome)...with NO MOTOR work since I built it!!!

I'm now in the process of performance building my two 2.5L's for this 21' econo-rocket project. The goal is 7000rpm for them... with my new props, it should see 100+ or so... Jim. http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

[Chris]

jr...

It's not worth it in my eyes. I get up around the redline and I'm gringing the entire time.

[jrumon]

CHRIS...what boat, motor, and set-up are you running...sounds like you might be a canidate for some more performance???

P.S.. Chris, buddy, pal, head honcho... can you also fix the thread title (since I don't have access)...to BEYOND the RPM range??? Sorry I forgot to check the spelling thing again... Jim.

[175checkmate]

Fixed it for ya, don't worry I can't spell any better.

[jrumon]

175Checkmate... did you get your boat back together??? Curious how yours is running with the mods... http://www.checkmate-boats.com/infopop/emoticons/icon_confused.gif

I'm hoping for for Momorial Day weekend to "break in" this twin engine monster... The motor mods and a fresh set of trick 31 Clevers should see that 100+ mark with some dial-in time!
http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/bounce.gif
Get this...My wife "freaked" when she saw my Nitrous Bottles sitting in the garage by the boat...Hmmmm....I wonder where the NOS Nozzels go anyway??? I like speed , but I'm not that crazy!!! "No Fear Dear"...I'm selling the bottles to a buddy for his drag car (but thanks for the kind thoughts)...she knows me too well!

ANYONE ever run Nitrous on an outboard???? I had a highly modified 2.4 Bridgeport on a 20' Vegas XT that had a NOS Nitrous system on it from the previous nut case... I never braved the "button"...the boat ran sweet at about 95-97mph on natural power. I needed more PROP and IRON NADS before I would use the NOS anyway...BUT...I always wondered what would happen when you LET OFF THE BUTTON at 100+mph...??? Any thoughts? Jim.

[JUPITER PULSARE]

LET OFF THE BUTTON??? 2 WORDS-GET WET!!

[Chris]

Geez,

Talk about spelling.

I meant to say cringe, not gringe. http://checkmate-boats.com/groupee/forums/ws/,s,8626072361/Graemlins/yell.gif

jr....I'm not a performance demon. I just have a stock Pulse 170 with an XR4. We mostly waterski and tube. http://www.checkmate-boats.com/infopop/emoticons/icon_smile.gif

[INXS]

I seen a boat magizine comparison between a XB 250 and a V-Max 066. Yamaha rigged the 066 to spin 600 RPMs over their recomennded top range. It ran less then !MPH slower then the Merc.. I think their rec. top range, 5,600, is just to help them get thru the warranty with less problems. $$$$$ It's just saying them money and biulding up their reliability!
PS, the top speeds on the bass boats they used, 21 Ft. 1,300 lbs, use 82 MPH, not bad.

[jrumon]

Jupiter...I wouldn't be afraid to push the NOS button...It's that sudden "braking action" at 100+ that has had me mistified...I just see it as a DEATH WISH or WHAT??? http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/jpshakehead.gif

Chris...thats a great boat... easy to trailer and loads of fun for the money (although I'd have a 200 on it with the 150 cowl)... http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/sssh.gif

Inxs...Yes, I think all motors will run over that "suggested max rpm range"...Your right, they do it for warrenty and tune stock motors to get their power curve in before that. Keep in mind that the factory stock motor rpm range is designed to run WIDE OPEN for days if necessary without failure. If your boat will keep pulling RPM past that factory rpm range and your getting for MPH...go for it!!! That additional 500 rpm is not going to hurt a thing as long as the motor's in good shape and the prop is keeping it "loaded up" (not a ski prop with no load so to speak)... http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/thumb.gif

[Chris E]

I'm just going to be the wet blanket here. If you do choose to run over redline go right ahead. But don't, I repeat DON'T come crying into the service department when (not if) you blow the thing up looking for a new powerhead covered under warranty. Optis, EFI etc. all have an ECM in them and it tells me EXCTLY what you were up to before the connecting rod parted ways with the piston. How many minutes were run at different RPM ranges and what went on during break in. The engine manufacturers can tell by looking at the block what was going on too (and yes they do want the blocks back). As someone who has been submitting warranty claims for the last 7 years, I can tell you before you unhook the trailer whether or not you have a claim.

After you're warranty has expired, by all means over rev 'em all day long - I like engine rebuilds - good money for the service department.

My own recommendation: Prop properly, run at 3/4's throttle, and reliablity will never be an issue. I speak from experiance here, my dad's 1968 larson has never given us one minute of trouble since he bought it in 1973.

[INXS]

Chris E,
Good points, also it's better to run a 250 HP @ 80% WOT then to a 225 at 100%. So if possible go with a a motor that will give you the speed you need without running your motor flat-out!

[Craig]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by INXS:
Chris E,
Good points, also it's better to run a 250 HP @ 80% WOT then to a 225 at 100%. So if possible go with a a motor that will give you the speed you need without running your motor flat-out! <HR></BLOCKQUOTE>

FYI: I'm not a mechanic by trade, but I know enough about boat motors to tell you this. You need to prop your boat so it runs in the max recommended rpm range at 100% WOT not 80% throttle. You'll cause problems by doggin your motor as well.

This doesn't mean that you need to run 100% WOT all the time, but you need to set it up so it's capable of reaching max rpms.

-Craig

[INXS]

Craig,
I'm also not a mechanic nor a expert. If you re-read my post you will see I said if you want speed then if possible you should run a 250 HP motor rather then say a 225. It's a little easier on the motor. I didn't mention anything about propping the motors, just more HP=more speed!It's just common sense!

[Craig]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by INXS:
Craig,
I'm also not a mechanic nor a expert. If you re-read my post you will see I said if you want speed then if possible you should run a 250 HP motor rather then say a 225. It's a little easier on the motor. I didn't mention anything about propping the motors, just more HP=more speed!It's just common sense! <HR></BLOCKQUOTE>
My mistake. I did not understand that you were trying to make a point that more HP = more speed. When you stated that you should not run your motor “flat out” I assumed you meant don’t run it WOT.

I’m just saying running WOT is not a bad thing. On marine engines that’s where the max HP is. A 225hp motor running WOT is making approx. 225hp, a 250hp motor running ¾ is making around 175hp or less.

But, yes I agree that running a motor at ¾ throttle is easier on it then running WOT. I do not agree with earlier posts in this thread that it’s OK to run 500 rpms past the rev limit, although I think the point JR was trying to make is that you should not have major problems if you run responsibly. It’s a pain in the ass, though. In order to run up past the rev limit you need to do some things different to keep it safe, which in my eyes aint worth it. You need to first eliminate the rev limiter and then remove your oil injection.

-Craig

[INXS]

Craig,
Good point about the about the HP curve, I also could have used say a 200 HP to a 250 Hp comparision. From what I hear you can run WOT allot longer in the rec. RPM range then you can if you run over the rec. range. I had a 87 Enchanter with a 260 I/O with a cleaver Prop.. It spun about 4,900 rpms and was put on the boat after 250 hrs, I used it for about 100 hrs and sold it. The person that bought it put on about 100 hrs and blew the motor. It ran great but the higher rpms will shorten the life of the motor some. I only ran it WOT for short sperts but the guy that I sold it to ran it hard!

[jrumon]

Hey guys...

Your all correct in some way or another...But this whole thread was aimed at getting a few more MPH out of your PERFORMANCE boat... I was refering to OUTBOARDS (not I/O's), and refering mainly to the common carb 2.4L and 2.5L Merc's.

Yes...the new motors "black box" records everything...and they have "rev control" built in already to prevent over-rev's. As far as warrenty goes... most of us aren't lucky enough to have a warrenty left anyway... http://checkmate-boats.com/6/ws/,s,8626072361/Graemlins/jpshakehead.gif

SO HERE'S MY DISCLAIMER... If your an IDIOT, if you run crappy oil, lame grade gas, run WOT for long periods of time, free-spool it (wave jumping or cavitation)...YES...You will have parts failure at one point or another with a stock motor.

I guess thats what seperates us guys who turn a wrench and look for that extra speed over the guys who shell out Mega Bucks on a "hot shot motor" that don't know how to change they're own spark plugs...(service departments LOVE those guys)! I believe that's what seperates us PERFORMANCE BOATERS from the Bayliner owners!!!