RPM's????

[Bayou Native]

What should my 1983 115 evinrude be turning?

 

[emdsapmgr]

Re: RPM's????

The factory originally rated this engine to operate between 4500 and 5500 rpm. Current thinking is that an engine run at the lower end of the normal operating range is lugging. Preference is to run in the upper end of the normal range, or 5500 to 5600. Above 5600 the hp/torque starts to drop off significantly. It was rated at 115 crankshaft hp at 5000.

 

[Bayou Native]

Re: RPM's????

Thanks for the info I appreciate it.

 

[Bayou Native]

Re: RPM's????

Is there a way to make my engine more fuel efficient without losing power???

 

[petryshyn]

Re: RPM's????

Is there a way to make my engine more fuel efficient without losing power???

Pretty subjective question.....A good tuneup may help providing its "out of tune" now...

Also, what RPM are you getting at WOT? Your prop pitch and design also plays a role....

Cheers

 

[emdsapmgr]

Re: RPM's????

Years ago, OMC promoted a "fuel saving" throttle position for economic boat operation. This still works for your model year, but is probably not part of any owner manual information. The theory is to slightly reduce the throttle handle from full throttle when on plane. Something like 7/8 throttle. What happens is that the throttle butterflys close somewhat, but the spark stays at full advance. This is the most fuel efficient throttle position if you are doing long cruising.

 

[kenmyfam]

Re: RPM's????

Is there a way to make my engine more fuel efficient without losing power???

Get someone to tow you and leave yours switched off !!!
1980's 2 stroke outboards were not built for their fuel efficiency. Any modification to improve fuel usage could be harmful to your motor in my opinion.

 

[bob johnson]

Re: RPM's????

I am a little confused...... I have read here that the motors want to run at their sweet spots in the upper rpm range ...otherwise you might be over loading your motor running at lower rpms.

does this apply to a motor whos WOT is in the correct range...say 4500-5500

but you only cruise at 4000 rpms???? but still on plane

is that hurting the motor?????? doesnt seem like it should.

but over and over, I hear here that the motor should be run at the correct rpm range or you are going to kill the motor

my motor it is said has a range for WOT of 4500-5500, but i have read over and over it likes the high 5,000's..like 5800 rpm!!! I have even heard 6000 rpms!!

it is a 60 degree looper 115 hp 1995 model.

I got a prop that will set me at 5300 rpms at WOT and a lower pitched prop that sets me at 6200 rpms at WOT

(I will keep the lower pitched model in case i need to really load up the boat( figureing the motor wont make it up to those rpms fully loaded.)

but am i in danger when of damaging my motor, running at 4000 rpms in cruise mode... on plane.. when i am using the 5300 WOT prop??

if the danger only applies to WOT rpms....does that imply you SHOULD run at WOT as often as possible???????????????

bob

 

[emdsapmgr]

Re: RPM's????

I think you are confusing the principles of properly pitching the prop vs your question on fuel economy. You can do both at once. Prop the engine to run WOT in the upper end of the normal operating range as specified in your owner's manual. For fuel economy pull it back to around 7/8 throttle. As long as it is propped right, it won't hurt it to run/cruise at a slower speed.

 

[Fl_Richard]

Re: RPM's????

I don't think the efficiency question means you should cruse around at 7/8 throttle. That's not going to be the most efficient speed. Usually cruse speed is around 32-4000 RPM. The WOT RPM is used to determine that the boat is propped correctly. By determining that the WOT throttle is at the proper range you know the prop is OK for all operating RPM's. from idle to WOT. This doesn't mean it's ok to drive around all day at inefficient speeds that obviously lug the engine.

My '95 150's get better economy at 3400 RPM about 1.7 KMPG (twins) and about 1-1.2 KMPG at WOT. Worse as conditions deteriorate.