volvo tmd40a prop

[macorre4]

hi i need to know what size prop with what pitch is needed for this motor with 280 outdrive i have the motor in a 2000 seaswirl stripper 2600 and i gett the motor wot at 3000 rpms but cant get the boat to plain out please let me know thanks

 

[steelespike]

Re: volvo tmd40a prop

For me I need as much help from you as possible.Volvo numbers can be a mystery.
As near as I can tell the TMD40A is a deisel with a max hp of 124 depending on the year.
The Seaswirl Striper weighs at least 4200 lbs.My info is nill on gear ratio,usually stamped on the outdrive, and I'll need the max rated rpm and the speed at 3000. and the prop size. I would think that motor would be working mighty hard to plane that boat.

 

[macorre4]

Re: volvo tmd40a prop

well according to the person that sold that motor to me told me that the motor is a 140hp and he also told me he believes that the gear ratio is 1.61 to 1 thats all i got

 

[steelespike]

Re: volvo tmd40a prop

It's possible A Volvo expert may know just what prop is needed but we can't tell if you have a motor issue
hull issue, or a prop issue without certain criteria. If I rememberr right the production for the TMD40A ended in 84.
The motor may have labels telling us the maximum rpm rating.And again the gear ratio may be stamped on the out drive.
You can estimate the ratio by turning the motor by hand (with the comprtession released )and count the revolution in one turn of the prop. We also need to know the present prop size.Again usually a mystery to all but a Volvo expert.Hopefully the size is near
the base of the blades or under the prop nut.
I stumbled on your post at The Hull Truth. They can probably tell you what the motor should do
and even what prop may be needed but without the info I asked for they can't tell why your motor isn't performing.In my research it appears the gear ratio in a 280 outdrive is 2.15 while the 290 appears to be
1.61.However my info is very limited.
Do you know what the motor was in and did it have the 280 outdrive?
If it was in a relatively light boat the prop would be wrong for your boat.

 

[Don S]

Re: volvo tmd40a prop

I stumbled on your post at The Hull Truth.

He also has a post here, in the diesel forum. With a lot of background. http://forums.iboats.com/showthread.php?t=527600

 

[macorre4]

Re: volvo tmd40a prop

hi that motor was in a 28 ft uniflite with twin diesels and the outdrive that was on it and is still on the motor is the 280 outdrive i was told that the 280 has the 1.61to 1 ratio

 

[steelespike]

Re: volvo tmd40a prop

If the prop is from a twin its likely too much prop. If you could get it to plane, perhaps a couple of people at the bow,
and get us the prop numbers and wot rpm and speed it would be easier to estimate a prop.

 

[O-fishal]

Re: volvo tmd40a prop

Heres the VP prop guide
http://www.volvopenta.com/SiteCollectionDocuments/Penta/Propeller guide/Propeller Guide.pdf

Are you a 280sp or dp? If an sp you might want to look for a dp lower

 

[O-fishal]

Re: volvo tmd40a prop

Ive never used this one but you can try it see if it works for you, there are tabs at the bottom of the page that you have to click and enter the data might work????
http://www.alberg30.org/maintenance/MechanicalPropulsion/Propeller/propcalc.xls

 

[macorre4]

Re: volvo tmd40a prop

its a sp im thinking about putting a higher gear ratio outdrive on that motor the prop right now is getting changed increasing prop dia and decreasing prop pitch and if that help then our next thing is to increase the ratio from 1.61to 1 to a 2.30 to1

 

[steelespike]

Re: volvo tmd40a prop

While it is very likely a 1.61 you may want to confirm before a very expensive gear change.

 

[macorre4]

Re: volvo tmd40a prop

my friend has a outdrive with 2.30to1 ratio from his 4 cylinder he told me i could have so i believe with that gear ratio change it would help big time what do u think

 

[Maclin]

Re: volvo tmd40a prop

The diesels have a much lower top rpm than a gasoline 4 cylinder don't they? A diesel's power is torque down low, thus the lower numerical ratio drives for them. I think you would run out of rpm's.

 

[RogersJetboat454]

Re: volvo tmd40a prop

The diesels have a much lower top rpm than a gasoline 4 cylinder don't they? A diesel's power is torque down low, thus the lower numerical ratio drives for them. I think you would run out of rpm's.

+1

Play with prop pitch first before you even consider changing drive ratios. Just so you are aware, that ratio change in the world of I/O's is huge!

 

[macorre4]

Re: volvo tmd40a prop

ok the way ratios work is if the oudrive ratio is 2.30 to 1 that means every 2.30 revolution on the pro is 1 revolution on the motor so if the motor is at 3000 rpms the outdrive is spining at 6900 rpm compared to if it was a 1.61 to 1 at 3000 rpms it would be spining the prop at 4830 so its a big difference and we are changing the prop right now increasing the diameter and lowering the pitch

 

[Maclin]

Re: volvo tmd40a prop

I hope there was a question in there somewhere about how the drive ratio works because you have it backwards.

The engine turns 2.3 times for every 1 rotation of the prop.

The engine at 3,600rpm, which is top of range for the TMD40, with a 2.3 ratio drive spins the prop at approx 1,565 rpm. With a 1.61 ratio drive the prop spins at 2,236 rpm or so.

If you go with the 2.3 ratio your engine would never be able to hit the rpm's required to have any top speed at all in my opinion.

 

[Maclin]

Re: volvo tmd40a prop

Lowering the prop pitch = more takeoff grunt but less top speed.

You need to determine what the pitch is now before choosing a different prop.

Also be sure the engine is performing within specs or any prop change will just be a bandaid for a larger problem.

I would recommend that you do not compare your 120hp diesel with the same 120hp from a gasoline engine. Your HP is at 3,600rpm, the gas engines have to spin a lot faster, more like 4,800rpm to do the same thing.

 

[macorre4]

Re: volvo tmd40a prop

im sorry but i believe you are worng on the ratio part a mechanic gave me this info and my motor is a 140hp and also the mechanic told me that a drive from a 4cylinder has more rotation because of the smaller motor and less rmps and a drive from a 4 is 2.30 to 1 and also thats why a dp drive has a 1.93 to 1 because of the 2 props ahveing a counter rotation if a i am wrong then the expert is wrong im going to look into that info to see i dont know anything aout ratios so

 

[steelespike]

Re: volvo tmd40a prop

Calculator says 1.61 @ 3600 15% slip 15" if it can turn it 27 mph. at that low rpm slip could be higher. 13" 23.4. mph
2.30 @ 3600 15" 15% slip 18.4 Slip for 2.30 will very likely be higher than 15%
2.30 @ 3600 17" 15% slip 21.4 " " " " " " " " . " "
Props pitch is in inches A 15" would move 15" through a solid in one revolution But props slip in a liquid
measured in % of slip.Usually the higher the rpm the less slip.The higher the slip mumber the less it moves through the water. 1.61 the motor turns 1.6 times for each prop revolution 2.30 turns 2.30 times.
You don't need to understand intirely but its obvious that a 1.61 is faster if the motor can turn the prop fast enough to plane out.The lower pitch props are easier to turn but produce slower speeds.
My 15% slip is most likely low I just wanted to produce some numbers so you could see the results of a ratio change.
Its obvious that a 13" prop is faster with a 1.61 ratio than 15" with a 2.30.
You need to have a ratio that will let the motor move the boat and will have a prop that will work with that ratio.As suggested earlier if a ratio change is needed perhaps a 1.95 is a better choice.

 

[macorre4]

Re: volvo tmd40a prop

im sorry i dont understand anything about slip and 13" 15" 17" SO DOES THAT MEAN THAT ADDING A higher gear ratio will be better or worse