What is the best rpm/mph cruise for my new to me 250HP Suzuki?

[Mighty Sylvan]

You guys with 250hp, what do you cruise at?

Do you think engine life would be effected much by cruising at 4500rpm rather than 4000rpm? MPG seems very close when checking online.

 

[Gunsmith]

Higher RPM means higher piston speed , more piston travel during the same time frame = increased wear. So the slower the RPM theoretically the less wear.

 

[profisher]

I adjust my rpms to the load I have on board each day. With a light load...say me and 2 other guys I run 4200rpms...if I have a full load of 4 plus myself I will bump it up to 4400rpms. I'm nut running the engine in question but this applies to all applications. Run your engine where it sounds right for the conditions...there is no one setting for all conditions.

 

[Theb55]

I have a tendency to run my Yami around 5000. Still a lot of top end to go but I don't like to drag my feet getting to a fishing location.

 

[trendsetter]

Do you think engine life would be effected much by cruising at 4500rpm rather than 4000rpm? MPG seems very close when checking online.

Only slightly. The engine parts will wear out faster at higher RPM but remember that your boat will be moving faster at 4500 RPM vs 4000 RPM. So that means less time at cruise. So for example 30 minutes at 4500 or 35 minutes at 4000 the difference in wear will be small for the same distance traveled.

I cruise with my 2-strokes at 5500 - 6000 RPM for hours on end

 

[nedarb2]

find some reports online with va similar boat and start there. unless your insanly under powered youshouldnt be above 4500rpm.
you should be in the 3800-4300 rpm range to optimal cruise. take out a calculator and start working out your mpg using your gas flow and gps speed at 100 rpm incrments till you find your sweet spot.

forefficiency i run at 3800, big seas im down to 3400 offshore, speedier cruise when its nice im up to 4200

 

[Island Fish Lifter]

Have you sea trialed it yet? Did that prop work? I would have no prob running it at 4500. I ran the twins at about 4200 to 4400 most times. When your boat is comfortably up on step, that is where you want to run it. That will be the most efficient.. less boat in the water, less drag, regardless of rpms if its propped correctly.

What do you get for top rpms with that prop?

 

[Foxsea]

You guys with 250hp, what do you cruise at?
Do you think engine life would be effected much by cruising at 4500rpm rather than 4000rpm? MPG seems very close when checking online.

Mine's a 225 F (same block on 200, 225 & 250F's) on a 25' boat. WOT is spec'd between 5-6,000 rpm. I put on a new prop to keep rpms below 6,200 where the rev limiter cuts in. The boat stays on step in all conditions at ~ 3800 but I usually run at 4200 to 4400 - the sweet spot where it hums and seems to get the best cruising fuel economy. Fuel consumption goes up dramatically once rpms are 5000+. The sound difference reminds me of an old 4 bbl.carb opened up. As other have mentioned, loading and sea conditions will influence cruising rpm's and speed as well.

My understanding is that long engine life will be more correalated to correct propping, good filters and being a stickler for regular maintenance than the rpms you cruise at. Extended periods of idling are not likely helping engine life and neither would extended periods at WOT.

 

[Doug]

I agree with island Fish Lifter comment.

The rpms your engine should run at are based on creating the least amount of boat hull drag. My boat sucks gas if it's running between 18 and 27 MPH because of the hull drag, it's like being stuck in glue.

I ran a Yamaha 250 and to get the best fuel mileage I ran it at 5000 rpms @ 31+- MPH. With the new 300 Yamaha I run it at 4400 rpms at 31 mph and burn 2 gallon+ less than the 250 did.

 

[Mighty Sylvan]

Thanks for all the replies guys.
The prop is right on. It has a WOT of 6100rpm @ 41mph.
4000rpm=25mph
4500rpm=30mph
In any chop the hull feels best at 30mph but the boat is planing comfortably at 3800rpm with tabs down around 20-22mph for offshore.
There is a speed loss from the old 225hp 2stroke but it is very nice to have a motor so quiet with no smoke.

 

[Island Fish Lifter]

Thanks for all the replies guys.
The prop is right on. It has a WOT of 6100rpm @ 41mph.
4000rpm=25mph
4500rpm=30mph
In any chop the hull feels best at 30mph but the boat is planing comfortably at 3800rpm with tabs down around 20-22mph for offshore.
There is a speed loss from the old 225hp 2stroke but it is very nice to have a motor so quiet with no smoke.

Perfect...

 

[profisher]

Using your last post sea trial data I would guess that the 30 mph at 4500 will be the best cruise setting if the water conditions allow it. All of my planing hulled boats just seem to perform best at about 30 mph for ride and fuel economy. That goes back to what Doug and IFL said..at 25 mph you have more hull in the water...the ride may be a bit better but your using more fuel to get from A to B.