Wide Open a Problem?

tee-boy · May 12, 2004

Is there somehting wrong with running an o/b wide open for extended periods? Does this violate warranty-Assuming it is after break in?

jim dozier · May 12, 2004

Re: Wide Open a Problem?

As long as the engine is operating at the proper max rpm (not overevving or lugging the engine) most healthy outboards can run at WOT all day.

tee-boy · May 12, 2004

Re: Wide Open a Problem?

Good. I like to run wide open.

Jack Shellac · May 13, 2004

Re: Wide Open a Problem?

Yeah, two cycles are designed to be run at high RPMs. Just make sure you're not exceeding the max and are ideally in the top quarter of the RPM range at WOT. You won't be getting very good fuel economy, but it shouldn't hurt the motor.

tee-boy · May 13, 2004

Re: Wide Open a Problem?

Does the same hold for 4 cycles?

jim dozier · May 13, 2004

Re: Wide Open a Problem?

I have no personal experience with the four stroke outboards, but I do with their technology. Actually, the four stroke max rpms are usually higher than the two-strokes. They need to go to higher rpm to match the two-strokes power output. I drive an Acura Integra GSR automoblile which has the same technology as the outboards (tuned intake manifold, exhaust header, double-overhead cam 4-valve per cylinder VTEC). Actually, it has a much higher specific power output (1800cc or 110 cubic inches at 170hp stock). The outboards would be detuned versions of a high output auto engine (Suzuki 115hp OB is 1950cc or 119 cubic inches). My car redlines at 8100 rpm which it sees regularly. I have 107,000 miles on it and the engine is still singing its song. I would say that my original post above applies to a healthy four-stroke as well.

LubeDude · May 13, 2004

Re: Wide Open a Problem?

I would have to say that if you ran your car at 8100 RPM up an extend slight hill all day forever that you wouldnt have 107,000 miles on your car. Even if the hill was steep enough that you couldnt do any more than 6,000 RPM in fifth and whatever top speed that would give you, I think you would be over working your engine. I hold to: 4 stroke outboards were not designed to rum WOT all the time for extended periods. Could be though. Just my feelings, no profesional background on this subject.

quantumleap · May 13, 2004

Re: Wide Open a Problem?

I agree with the Dude! WOT isn't as hard on a 2 stroke as a 4. The oil lubricating a 2 stroke is constantly introduced into the system cool and fresh whereas a four strokes oil keeps getting hotter and less stable(to a small extent)the longer you run at WOT.

ddaigle · May 13, 2004

Re: Wide Open a Problem?

Newer motors are designed to handle higher rpms. Any motor whether 2 or 4 stroke is going to have hifgher stresses and wear the higher the rpm, but most can handle it for a long time. I used to run 4 stroke motorcycles at 6-7000 rpms all day with no problems and this was 20 years ago. Boat motors seldom see enough hours to really harm them. Just use good oils-preferably synthetics.

jim dozier · May 13, 2004

Re: Wide Open a Problem?

As I pointed out the OB are detuned versions of the high output auto engines. One reason they do this is to allow the marine engines to run at heavy loads and WOT. You give me a Suzuki or Yamaha or Honda 115hp and some money (quite a bit) and I will give you a 170hp outboard that probably will scare you but probably WON'T want to run at max rpm (~7500-8000) all day under a heavy load. Time will tell but I'm betting that the marine 4-strokes will hold up pretty well for a long time if they are run hard. Any engine's internals will wear longer at lower stresses, but how many of these engines 2 or 4 stroke wear out I wonder? Most of them get killed by overheating, corrosion, water intrusion, or some other non wear related problem. LubeDude I'm going to stick my neck out and say that if you took my car engine, put in a huge radiator, changed the cams and intake to reduce the hp from 170 to 115 at 6500 rpms and put it under a load that limited it to 6000 rpm in 5th gear it would hum along quite well for a long time. As it is, I travel the interstate at 4500-5000 rpm right now.

jim dozier · May 13, 2004

Re: Wide Open a Problem?

Quantumleap, without trying to rekindle the argument of 2 vs 4 stroke (I personally favor them both), I don't think that the lubrication system of a 4-stroke engine is in any way the limiting factor on rpm usage and ultimate engine life. High rpm piston scuffing can be a problem with racing two strokes, and Formula 1 4-strokes (albeit a bit different than OBs) run at 19,000 rpm on a dry sump oil system. It all depends on the engine design.

quantumleap · May 14, 2004

Re: Wide Open a Problem?

jimd, not trying to rekindle the Petro vs. Syntheic debate,