Rpm

[cameldownunder]

Hi

I have a question regarding my Prop/Engine/Boat config

The maximum RPM i got out of my Yamaha 4 stroke 60HP and Quintrex 475 bowrider is 5000 rmp (at about 45 kmh)

I see on a data-sheet that the engine should be able to go up to 6000 rmp (top speed just under 50 kmh)

As mentioned in the description, mine doesn't go past the 5000.

As per the rest of the Data of the sheet, the prop/engine/boat behaves exactly like described.

Any idea why i cannot go past 5000? (not that this is really a problem)

[GregL]

Hi

I have a question regarding my Prop/Engine/Boat config

The maximum RPM i got out of my Yamaha 4 stroke 60HP and Quintrex 475 bowrider is 5000 rmp (at about 45 kmh)

I see on a data-sheet that the engine should be able to go up to 6000 rmp (top speed just under 50 kmh)

As mentioned in the description, mine doesn't go past the 5000.

As per the rest of the Data of the sheet, the prop/engine/boat behaves exactly like described.

Any idea why i cannot go past 5000? (not that this is really a problem)

Hi

lots of small things can change it like weight in boat, water conditions, prop, engine heights ect ect.

MOre likely set up than anything.

Greg

[prawn*]

is the engine only new? maybe its hasnt completely loosen'd up yet but more then likely extra weight and hull shape or plane has something to do with it.. my 12ft tinny gets to 60km/h when i tilt the motor up abit but its hard to plane on windy day so when i drop it down a notch i only get about 50km...

[james1990]

you need to play with the props, go down in pitch maybe 2 sizes and that should get your WOT to about 5600RPM, your accel will also be improved due to this and overall economy will be better.

sharpened and ground SS props are the go for optimum performance as they have minimal grab on the water and cut a finer hole, however watch your legs if getting back into the boat after swimming etc... ive seen stitches as a result of carelessness

the package should have really been setup correctly by the dealer in the first place.

Edited January 20, 2010 by james1990

[a boat]

Hi, as the guys have said you are overproped or not set-up right if you can only see 5000 at WOT and you WILL hurt your engine. It is like driving a car up a never ending hill in top gear-the engine is lugging and not good for it at all. Also getting the revs right or set-up (engine height) right will make a huge difference to the way the rig performs.

Cheers,

Huey.

[ajb]

Don't mean to hijack the post but it's got me thinking, I have a tiller steer with no tachometer, is there a way to check the revs?? I'd like to know if I have the right prop (it's an 02 Honfa 25hp)

cheers

[a boat]

Hi ajb, you can get Tachos that connect to the high tension lead and they are not that accurate but give you an indication of what you are seeing at WOT. Your engine wants to be seeing about 5500-6000 to get the best out of it.

Cheers,

Huey.

[GregL]

Oh question regarding your 5000rmp hit me last night for ya, is your 5000rpm by just moving throttle control to max only, with zero trim?

To get max revs out of a boat you will need to trim the boat out while driving.

WHile watching a friend drive my boat once, he was asking me how I achieve higher running speeds with better feul economy than he dose when I drive, THen I noticed by just looking at the wake and the way the engines sounded that he had not used the trim. WHen using trim as well I get another 1000rpm and another 4kns out of the motors. NOw they hit 5950down wind and 5900 into the wind.

Greg

[MrGenius]

Oh question regarding your 5000rmp hit me last night for ya, is your 5000rpm by just moving throttle control to max only, with zero trim?

To get max revs out of a boat you will need to trim the boat out while driving.

WHile watching a friend drive my boat once, he was asking me how I achieve higher running speeds with better feul economy than he dose when I drive, THen I noticed by just looking at the wake and the way the engines sounded that he had not used the trim. WHen using trim as well I get another 1000rpm and another 4kns out of the motors. NOw they hit 5950down wind and 5900 into the wind.

Greg

As above, need to make sure you are adjusting the trim correctly before you even consider wasting money on another prop.

[jack]

Hi, as the guys have said you are overproped or not set-up right if you can only see 5000 at WOT and you WILL hurt your engine. It is like driving a car up a never ending hill in top gear-the engine is lugging and not good for it at all. Also getting the revs right or set-up (engine height) right will make a huge difference to the way the rig performs.

Cheers,

Huey.

G'day Huey my 90 etec is maxing out at 4700rpm now i have a 17" SS prop.

Now is there a factory prop that comes with them or is there a prop you can recommend?

i have a 5m half cabin boat

kind regards Jack

[a boat]

Hi Jack, BRP or any company do not supply engines of this HP with props becuase they do not have any idea of what hull that 90HP is going to go on. You too are overpropped and/or too low in the water. I imagine you have trimmed out like Greg has said because that can get a fair few more revs. We rig most I-3 E-TEC on hole no.3 and your engine wants to see 5000-5200 at WOT to be in its ideal RPM band.

PM me if you like and get the serial number of the engine and prop P/N and we can go from there.

Cheers,

Huey.

[cameldownunder]

Oh question regarding your 5000rmp hit me last night for ya, is your 5000rpm by just moving throttle control to max only, with zero trim?

To get max revs out of a boat you will need to trim the boat out while driving.

WHile watching a friend drive my boat once, he was asking me how I achieve higher running speeds with better feul economy than he dose when I drive, THen I noticed by just looking at the wake and the way the engines sounded that he had not used the trim. WHen using trim as well I get another 1000rpm and another 4kns out of the motors. NOw they hit 5950down wind and 5900 into the wind.

Greg

Yep, when I say 5000 max, that is when I just move the throttle to the max! Then engine is in the lowest position possible

When you say trim what do you mean? get the engine slightly out of the water?

Would that mean that at max rmp i squeeze the nose of the boat down?

[a boat]

Hi, when Greg talks trim, it is trimming the outboard up or out that raises the bow of the boat and therefore, due to less friction on the running surface of the hull, the engine will be able to rev more. WOT RPM needs to be confirmed with normal load and engine trimed out correctly. teh faster you go the more trim out you can run with.

Also as mentioned the engine mounting height can affect performance alot and when trimmed correctly the AV plate wants to be visible above the water.

Cheers,

Huey.

Edited January 21, 2010 by Huey @ Huett Marine

[mr475]

I have a Quintrex 475 Bayhunter with a 70hp Yamaha and it came with a set of instruments which include a trim indicator. This shows you how the boat is riding, i.e. whethe in a bow up attitude or bow down. Adjusting the trim to put the needle on the neutral position works well but I have found that at speed I can go a little faster if I trim the bow up a little more in smooth water.

Does your boat have one of these indicators? If so, it makes trimming a breeze.

But I have a different problem. My boat cruises at 50kph (indicated) at 4,000rpm. When I go to WOT, the boat surges forward and tops out at about 60kph with 2 aboard and canopy up. But the tachometer only increases its reading by 500 rpm, going to a max of 4500rpm.

The boat FEELS to surge and it SOUNDS like the revs increase by more than 500 rpm. Could it be possible that the tacho needle is sticking?

[a boat]

I have a Quintrex 475 Bayhunter with a 70hp Yamaha and it came with a set of instruments which include a trim indicator. This shows you how the boat is riding, i.e. whethe in a bow up attitude or bow down. Adjusting the trim to put the needle on the neutral position works well but I have found that at speed I can go a little faster if I trim the bow up a little more in smooth water.

Does your boat have one of these indicators? If so, it makes trimming a breeze.

But I have a different problem. My boat cruises at 50kph (indicated) at 4,000rpm. When I go to WOT, the boat surges forward and tops out at about 60kph with 2 aboard and canopy up. But the tachometer only increases its reading by 500 rpm, going to a max of 4500rpm.

The boat FEELS to surge and it SOUNDS like the revs increase by more than 500 rpm. Could it be possible that the tacho needle is sticking?

Hi Mate, yes that is possible and only way to know for sure is swap out the Tacho and see what the enw one does in the water.

Cheers,

Huey.

[jack]

Hi Jack, BRP or any company do not supply engines of this HP with props becuase they do not have any idea of what hull that 90HP is going to go on. You too are overpropped and/or too low in the water. I imagine you have trimmed out like Greg has said because that can get a fair few more revs. We rig most I-3 E-TEC on hole no.3 and your engine wants to see 5000-5200 at WOT to be in its ideal RPM band.

PM me if you like and get the serial number of the engine and prop P/N and we can go from there.

Cheers,

Huey.

cheers mate will do

[cameldownunder]

Does your boat have one of these indicators? If so, it makes trimming a breeze.

Doesnt have, but I could use the Compass, that is always horizontal.

Thanks a lot for the tips, I will try them out next time I go on the water.

[GregL]

Doesnt have, but I could use the Compass, that is always horizontal.

Thanks a lot for the tips, I will try them out next time I go on the water.

Hi Camel

The best trim on a boat is usually not flat running at a high speed. Next time you see a fast running bass or ski boat you will see that the nose of the boat looks low but thats only because of speed. Look closer and you will see the boat usually is only sitting on the last 1m of hull touching the water and the engine leg. In fact the driver trims a boat up to get it to run flat once on the plan. DIfferent speeds and water conditions change how much or how little trim is to be used.

You can use your trim at lower speeds too, in smaller craft when the wind and chop is up, trim the boat up to sheild you from the spray more so the nose isn't so low.

Once getting the feel of using the trim switch, your running times will be faster, your feul burn will drop and the ride will be alot smoother!

Worth mastering!

Greg

[cameldownunder]

THANKS !!!

Your info is really apreciated

Managed a 5500rpm and 50km/h

It´s like having a new boat !!!!!

Thanks again for all the cool tips.

[Berleyguts]

Excuse me, but what is WOT?

Thanks,

Baz

[Croydon]

Excuse me, but what is WOT?

Thanks,

Baz

Wide Open Throttle........