Yamaha 25hp 14ft semi-V rpm range question

[Pale_Horse_Idaho]

I tried searching but found 1,200 pages of people arguing over suggested range vs optimal range. Yamaha says 5000-6000 rpm's for my motor.

When I go out with the dog and myself my RPM's are 5800-5900. Add the wife to the mix and I'm running 5500-5580 rpm's

I recently sand-bar'd my lower pitch prop and its junk. Can I continue to run at 5500 or do I need to buy another lower pitch prop? Option two would be always leave the wife at home.

The motor sounds better at 5900 than it does at 5500. One additional question. Can I run down a large lake for 1hr @5900 rpm without stopping?

 

[FuzzyGrub]

As long as you are within the mfg wot rpm range, you should be good. You will notice a difference in not having the same "pull" out of the hole, that you did with the lower pitched one.

I only run at wot for short periods on every trip. Typically for long runs, at about 60-75% of top speed. I doubt that wot for 1 hour is going to help with longevity.

 

[Pale_Horse_Idaho]

As long as you are within the mfg wot rpm range, you should be good. You will notice a difference in not having the same "pull" out of the hole, that you did with the lower pitched one.

I only run at wot for short periods on every trip. Typically for long runs, at about 60-75% of top speed. I doubt that wot for 1 hour is going to help with longevity.

Ive tried going slower but the boat starts to drag in the water near 5000-4800 rpms. Your 60% 3,600rpm's target would be trolling speed and the nose would be pointing up at a 30 degree angle in my boat and not even be on a plane. I thought small outboards were made to run WOT all day?

The other posts Ive read said suggested range is not optimal and no one could agree on which was OK. I guess here we are again. The motor sounds like its running harder at 5500 than it does at 5900.

4,800 rpms at 80% is still dragging my boat through the water.

 

[airshot]

You might try trimming the motor or change your load position, sounds like you not up on as high of plane at the lower rpm. On small boats people often need to shift things around to get proper balance and often need to have their guests sit in a spot they may not like, but needed to balance the load. A 25 hp on a 14' tinnie should have no problem at all being up on plane at 4-4400 rpm if your load is balanced properly. The faster your boat gets up on plane at the lowest rpm (75% throttle) the less fuel your motor will use. Today's engines are made to run wot for long periods of time, but many of us old timers understand that pushing any engine to extreme will shorten its life. My max rpm is 5500 on my motor, I prop it to run 5600 with minimum weight, so when I have extra weight or people it will run in the proper range. I do watch my tach when alone, on long rides I hold my rpm to around 48-5000 to be safe, on really long cruises down to 44-4600. Not that much loss of speed to help the engine last longer in my opinuon.

 

[FuzzyGrub]

Ive tried going slower but the boat starts to drag in the water near 5000-4800 rpms. Your 60% 3,600rpm's target would be trolling speed and the nose would be pointing up at a 30 degree angle in my boat and not even be on a plane. I thought small outboards were made to run WOT all day?

The other posts Ive read said suggested range is not optimal and no one could agree on which was OK. I guess here we are again. The motor sounds like its running harder at 5500 than it does at 5900.

4,800 rpms at 80% is still dragging my boat through the water.

60-75% of top speed @ WOT. Not of RPM. So if your wot top speed is 30mph, cruise about 18-24mph.

 

[Crazyboat]

If you damaged the prop, get it repaired or replaced. If it's a nick don't fuss over it. If you get 5,900 RPM with a light load IMO you are propped right or as near to perfect as you can. Adding the Mrs. drops your RPM down to 5,500, you are still fine, but I agree, things sound better at 6K.

If you are studious, get a lower pitched prop for when the wife joins you for higher RPM and just be mindful not to outrun yourself when alone and keep it at or under 6K.

 

[MDCrappie]

Ive tried going slower but the boat starts to drag in the water near 5000-4800 rpms. Your 60% 3,600rpm's target would be trolling speed and the nose would be pointing up at a 30 degree angle in my boat and not even be on a plane. I thought small outboards were made to run WOT all day?

The other posts Ive read said suggested range is not optimal and no one could agree on which was OK. I guess here we are again. The motor sounds like its running harder at 5500 than it does at 5900.

4,800 rpms at 80% is still dragging my boat through the water.

You're definitely not set up correctly, or you are WAY overloaded. Can you take a picture of the stern with the motor in running position? Might be able to help you out. Also how much weight do you normally add? (People, tackle, coolers, etc)

 

[Zum]

I have an old 30hp Mariner(Yamaha 1987). Its either idling or WOT, very seldom do I run in between those 2 positions.
I use 3 different props, depending on load, I like to stay in the high 5's.
I think your fine at 5500. Also think an hour at WOT is fine or atleast I have never had an issue.
I bought a compression checker off Amazon a few days ago,to test my motor...110 on both cylinders...guess I cant justify a new motor.
I do kinda want a 4 stroke but just for the quietness.

 

[wmk0002]

Most people may disagree, but I don't mind pushing a 2 stroke motor above the recommended rpm range a bit. I try to keep my outboards in tip top shape primarily ensuring water pump is in order and carbs aren't running lean, I run ethanol free gas, add Yamalube, etc which is critical plus I have a lot of them in case I was to burn one up lol. I probably wouldn't do that on 4 strokes plus the only 4stroke I have is a new efi one so the computer will keep it from over reving even I wanted it to.

I'd get at least 2 props to have on hand. Have a nice prop sized for WOT for your typical setup and then a cheaper one sized for your heavier load setup. They are a breeze to swap out and you will stay on top of fishing line that could eat up your prop shaft seals. Keep both on the boat so you have a back up on the water too.

 

[turbotodd]

On most of the yamaha's you can get away with going a couple hundred RPM over their recommended max. I'm at 6150-6200 on mine (F25 EFI) and it works well on my boat. You don't have to run it there all the time, I typically cruise at 22-24 mph at 4500-4800, which is where it gets the best fuel economy. On cool days with just the right chop, it'll go into fuel cut if I'm trying to get to the ramp in a hurry (fuel cut=rev limiter). Ease off the throttle a little, no big deal.

You didn't say whether it was 2 stroke or 4 stroke, or which one of either one-as there are at least 5 different types of 25hp yamaha. That said, all 4 stroke from 99-2017, you can safely run 6200 RPM for a while so long as the engine is in good shape. 2017+, fuel cut at 6200 so it won't let you run there, it will shut the injectors off briefly until RPM drops below 6150 then back on-just a split second. On all of the 4 stroke engines regardless of brand, you need to prop it so that it can run right up to, and maybe a little over, the maximum recommended RPM. On yamaha, they say 6000 is max on most of them (exception F70, which is 6200)-I am not scared to allow 6100 or so, as said. Main reasoning is that 4 stroke engines tend to make their horsepower with RPM-and lugging them can and sometimes does result in "issues" (milking the oil, making oil, poor performance, poor fuel economy, overheating sometimes, etc)--it's all hard on the motor. On the 2 stroke engines, most of them are 6000 MAX as well, 6250-6300 is the limiter, and I'm not scared to run right up against it so long as I have earplugs. However, they are a little "less sensitive" to lugging, although it's still hard on the engine over time.

agree, having a spare prop is a good thing. One can be a lower pitch for loading, other one can be higher pitch for light load. Throw a rue pin in the cotter pin hole and carry a 22mm or 7/8 wrench. I have one that I just cut off. They don't need to be but about 25 lb-ft, not very tight really so a short wrench that fits in the tackle bag works well. I keep a 12" on the motor most all the time and a 10.5" (old style stock aluminum prop) as a spare. So far haven't needed the spare, but you just never know.