SampoSam
Member
Does anyone have a Monterey 250cr with Yanmar 240 diesel engine as need to discuss planing issues ?
Does anyone have a Monterey 250cr running a Yanmar 240 diesel ?
- Thread starter SampoSam
- Start date
QBhoy
Well-known member
I was familiar with a friends boat, this exact model. Might be able to compare the basics. Drove her a few times during his ownership.
ChromeDome
Well-known member
No - know some with the engine but in different boats and on shafts
Neeves
Well-known member
Bilgediver
Well-known member
I. would post this in crusersform.com more likely to find a few owners in the USA
www.cruisersforum.com
SampoSam
Member
Thanks everyone will try those forums suggested !
SampoSam
Member
Thanks for your reply. Can i ask what it was like getting up on the plane and what the top end speed was ?. Did you fin the boat heavy and more weight toto aft ?- do you know if the outdrive was a Bravo 1 and would you know prop size ?
ChromeDome
Well-known member
Now we are getting closer 
A planing hull at a given Gross Weight (GW) can be pushed to a certain top speed by a given number of HP.
If the Monterey is some 2400 kg dry (manufacturer stated), 240 hp will be able to push it to 30+ knots; provided clean hull, engine up to specs, propeller clean and correct, and a calm sea.
Since the GW will be (boat+crew+gear+equipment+fuel+water+food+beverages) it will be way more than 2400 kg. If the ready-to-go weight is 3000 kg the theoretical top speed is some knots lower and the hole shot (acceleration from idle, in gear) will be notably slower.
To know if you have the right propeller you simply read the tachometer at full throttle, with your normal load, it should reach 3300 rpm for your engine. When so, the load on the engine is correct as per the manufacturer, also at other speeds.
If all is well and it still struggles to get on the plane (at full throttle for up to a minute), there are a few ways to go:
If you do not reach the 3300 rpm with your normal GW, you can change the pitch (effectively the "gear range") by having the prop altered or getting a new. Each inch less pitch will add 200 rpm to the engine - and vice versa - in theory (only a real-life test will show, so getting the prop from a dealer that will allow you to test/swap is safest). You'll see that props normally comes in 2" increments meaning that 400 rpm is the least change in rpm you can get. If having the prop altered, you can get any change you want (almost).
If tempted by exotic props (stainless, tailored etc.) you'll notice different prices. Very. Just remember that 90% of prop performance is down to the design, the rest can be attributed to the material.
Similar subject discussed in this thread.
A planing hull at a given Gross Weight (GW) can be pushed to a certain top speed by a given number of HP.
If the Monterey is some 2400 kg dry (manufacturer stated), 240 hp will be able to push it to 30+ knots; provided clean hull, engine up to specs, propeller clean and correct, and a calm sea.
Since the GW will be (boat+crew+gear+equipment+fuel+water+food+beverages) it will be way more than 2400 kg. If the ready-to-go weight is 3000 kg the theoretical top speed is some knots lower and the hole shot (acceleration from idle, in gear) will be notably slower.
To know if you have the right propeller you simply read the tachometer at full throttle, with your normal load, it should reach 3300 rpm for your engine. When so, the load on the engine is correct as per the manufacturer, also at other speeds.
If all is well and it still struggles to get on the plane (at full throttle for up to a minute), there are a few ways to go:
- Make sure the sterndrive is trimmed all the way down/in (you probably know already, but here goes):
- Remove dead weight from the boat (free, very efficient).
- Move weight forward (even crew until on the plane)
- Go in a straight line until planing.
If you do not reach the 3300 rpm with your normal GW, you can change the pitch (effectively the "gear range") by having the prop altered or getting a new. Each inch less pitch will add 200 rpm to the engine - and vice versa - in theory (only a real-life test will show, so getting the prop from a dealer that will allow you to test/swap is safest). You'll see that props normally comes in 2" increments meaning that 400 rpm is the least change in rpm you can get. If having the prop altered, you can get any change you want (almost).
If tempted by exotic props (stainless, tailored etc.) you'll notice different prices. Very. Just remember that 90% of prop performance is down to the design, the rest can be attributed to the material.
Similar subject discussed in this thread.
SampoSam
Member
Now we are getting closer
A planing hull at a given Gross Weight (GW) can be pushed to a certain top speed by a given number of HP.
If the Monterey is some 2400 kg dry (manufacturer stated), 240 hp will be able to push it to 30+ knots; provided clean hull, engine up to specs, propeller clean and correct, and a calm sea.
Since the GW will be (boat+crew+gear+equipment+fuel+water+food+beverages) it will be way more than 2400 kg. If the ready-to-go weight is 3000 kg the theoretical top speed is some knots lower and the hole shot (acceleration from idle, in gear) will be notably slower.
To know if you have the right propeller you simply read the tachometer at full throttle, with your normal load, it should reach 3300 rpm for your engine. When so, the load on the engine is correct as per the manufacturer, also at other speeds.
If all is well and it still struggles to get on the plane (at full throttle for up to a minute), there are a few ways to go:
- Make sure the sterndrive is trimmed all the way down/in (you probably know already, but here goes):
- Remove dead weight from the boat (free, very efficient).
- Move weight forward (even crew until on the plane)
- Go in a straight line until planing.
If you do not reach the 3300 rpm with your normal GW, you can change the pitch (effectively the "gear range") by having the prop altered or getting a new. Each inch less pitch will add 200 rpm to the engine - and vice versa - in theory (only a real-life test will show, so getting the prop from a dealer that will allow you to test/swap is safest). You'll see that props normally comes in 2" increments meaning that 400 rpm is the least change in rpm you can get. If having the prop altered, you can get any change you want (almost).
If tempted by exotic props (stainless, tailored etc.) you'll notice different prices. Very. Just remember that 90% of prop performance is down to the design, the rest can be attributed to the material.
Similar subject discussed in this thread.
SampoSam
Member
Thanks ChromeDome very helpful. I have recently tested with 1 other on board and only 1/4 fuel. Water tank full but no other weight except tools who i guess are quite heavy.only tested recently ( after engine overhaul) in choppy and windy conditions. Question should i use trim tabs to help get up on plane ?
SampoSam
Member
Now we are getting closer
A planing hull at a given Gross Weight (GW) can be pushed to a certain top speed by a given number of HP.
If the Monterey is some 2400 kg dry (manufacturer stated), 240 hp will be able to push it to 30+ knots; provided clean hull, engine up to specs, propeller clean and correct, and a calm sea.
Since the GW will be (boat+crew+gear+equipment+fuel+water+food+beverages) it will be way more than 2400 kg. If the ready-to-go weight is 3000 kg the theoretical top speed is some knots lower and the hole shot (acceleration from idle, in gear) will be notably slower.
To know if you have the right propeller you simply read the tachometer at full throttle, with your normal load, it should reach 3300 rpm for your engine. When so, the load on the engine is correct as per the manufacturer, also at other speeds.
If all is well and it still struggles to get on the plane (at full throttle for up to a minute), there are a few ways to go:
- Make sure the sterndrive is trimmed all the way down/in (you probably know already, but here goes):
- Remove dead weight from the boat (free, very efficient).
- Move weight forward (even crew until on the plane)
- Go in a straight line until planing.
If you do not reach the 3300 rpm with your normal GW, you can change the pitch (effectively the "gear range") by having the prop altered or getting a new. Each inch less pitch will add 200 rpm to the engine - and vice versa - in theory (only a real-life test will show, so getting the prop from a dealer that will allow you to test/swap is safest). You'll see that props normally comes in 2" increments meaning that 400 rpm is the least change in rpm you can get. If having the prop altered, you can get any change you want (almost).
If tempted by exotic props (stainless, tailored etc.) you'll notice different prices. Very. Just remember that 90% of prop performance is down to the design, the rest can be attributed to the material.
Similar subject discussed in this thread.
SampoSam
Member
Also i have a 24 inch prop with 14.5 inch diameter. So as i am getting full throttle perhaps i should look at a 22inch prop to get out of the hole ? ie less revs but more push - correct ?
ChromeDome
Well-known member
Check the linked thread.
Why carry a tank full of water? Get it out until needed. Tools also: out while testing
I presume boat hull and drive is clean - completely clean?
What rpm do you get at full throttle? 24" pitch and 3300 rpm? If at all possible use a second tacho to eliminate false readings.
What is the gear ratio in the Bravo-1 drive (should be stated on the drive upper part)?
Maths:
I your gear ratio is the common 1.65, 3300 engine rpm will be reduced to 2000 prop shaft rpm. 24" forward movement per turn will then give you a speed of 39,5 knots.
Admittedly there will be some prop slip, but if these are your figures I'd check the tacho.
Do you know what the engine overhaul comprised and if it was dyno tested after?
Why carry a tank full of water? Get it out until needed. Tools also: out while testing
I presume boat hull and drive is clean - completely clean?
What rpm do you get at full throttle? 24" pitch and 3300 rpm? If at all possible use a second tacho to eliminate false readings.
What is the gear ratio in the Bravo-1 drive (should be stated on the drive upper part)?
Maths:
I your gear ratio is the common 1.65, 3300 engine rpm will be reduced to 2000 prop shaft rpm. 24" forward movement per turn will then give you a speed of 39,5 knots.
Admittedly there will be some prop slip, but if these are your figures I'd check the tacho.
Do you know what the engine overhaul comprised and if it was dyno tested after?
Last edited:
SampoSam
Member
yes clean hull and ( took it out the water month 2 months ago.Getting around 3,800 rpm tested with a taco tester yesterday. Re water and tools ok will drain tank and remove tools and see how it goes. I will also try 22 inch prop
SampoSam
Member
its a bravo 1 not x ( if that makes any difference ?) i am not able to find the ratio but believe it to be 1.5
SampoSam
Member
i am told should try 26 inch prop i.e. two up ?
SampoSam
Member
or maybe 22inch ( two down) ?
ChromeDome
Well-known member
You need to know the true rpm at wot before deciding on a new prop.
And, btw. to measure speed by GPS (phone app, chartplotter or something)
And, btw. to measure speed by GPS (phone app, chartplotter or something)
ChromeDome
Well-known member
Did you sense a slip of the prop when testing (as in the prop spinning faster than the boat acceleration)?
What prop design do you have? On a Merc drive it was Quicksilver from new. Number of blades, anything stamped into the hub?
What prop design do you have? On a Merc drive it was Quicksilver from new. Number of blades, anything stamped into the hub?
ChromeDome
Well-known member
Hang on:
If 1,5 gear ratio and 3800 rpm (500 above manufacturer recommended max) you'll be turning the 24" at 2533 shaft rpm which calculates to 50 knots. Huh?
Can you check figures at your end, please
If 1,5 gear ratio and 3800 rpm (500 above manufacturer recommended max) you'll be turning the 24" at 2533 shaft rpm which calculates to 50 knots. Huh?
Can you check figures at your end, please