Volvo D3-150

[tlkenyon]

Just wondering....

I have a Volvo D3-150 in my R25SC. The D3 comes in various flavors, with HP rating up to 220. All the specs for the D3 are, or appear to be, identical (bore, stroke, etc, etc) except for the WOT rpm. Based on what I could find, the fuel pumps even seem to be the same. The higher ratings just seem to spin faster.

This makes me wonder if there is a way to get more out of my D3-150 without major changes...perhaps just software? There are obvious warranty issues, but the warranty is not gonna last forever.

Last week on the Mississippi I sure could have used a few more mph trying to pass that tow upstream....

MORE POWER!!

TK

 

[knotflying]

I am not as familiar with the D-3 as yanmar, but you seem to be on the right thought process a chip upgrade should increase horsepower, but remember, then you may have to do something about prop pitch.

 

[tlkenyon]

Seems to me that the faster the prop turns, the faster the boat goes...or am i missing something? It is the top end that I am looking to increase. Given the shape of the hull, it should handle a few more mph safely.

 

[Andrew Custis]

The engine manufacturers are very careful about this. From the engine side, we have to order the engine HP specific per the boat as they will not allow us to change ratings. It seems easy but it is not possible from our end.

Good question!

 

[tlkenyon]

Understood...it didn't really expect it from your end, and I do not think anything will happen on my end until the warranty runs out. My wrench-head brother is chomping at the bit to do a "chip" amd tinker othewise, but I think "wise" leaves it as-is for the time being. Kinda make you wonder, though.

 

[Just Dreamin']

TK, we have a R25 classic with a Cummins-Mercruiser QSD 2.0L 150, Mercruiser now offers the QSD 2.0 with a horsepower rating of 200+. After looking at all the specs it appears to be a ECM software change. However, a couple of areas which come to mind which may or may not be effected by a ECM or chip upgrade would be air intake and exhaust.
I think most boats have their air intake requirements designed to a specific sized engine; therefore, if one upgraded the engine horsepower would more intake air be required for the engine to operate efficiently? Also, would the exhaust system need to be resized to handle a potentially higher exhaust back pressure from increased exhaust flow?
I am not familiar with the Volvo but these are a couple of areas I would look into before doing any type of upgrade.

 

[knotflying]

Seems to me that the faster the prop turns, the faster the boat goes...or am i missing something? It is the top end that I am looking to increase. Given the shape of the hull, it should handle a few more mph safely.

Yes, you are missing something, more horsepower does not necessarily mean more RPM. Horsepower is an acquired strength at a certain RPM. Prop pitch is the angle at which the prop bites the water. You want the bite of the prop to be able to push the boat faster and hence you would require more horsepower. So, if you increase horsepower you would want to increase the prop pitch to coincide with the increased horsepower. The engine will use that horsepower to move more water and because of that there will be more load so the RPM's won't necessarily increase, but your speed will because you are using the extra energy to bite into more water. I am not a physics major, but I am a pilot and many of these same principles apply with prop angle, airspeed and lift.

 

[tlkenyon]

I do understand that more HP does not always mean more rpm, but in the case of these particular engines, the higher ratings turn at higher rpms, and would thus turn the prop faster, making the boat go faster. Additionally, with a heavy load, the higher hp would allow maintaining higher rpms (thus prop rpms) to maintain speed.

Interesting....as far as intake and exhaust, the higher ratings (as in the R27 w/ the D3-200) look to have the same intake and exhaust parts.

Ahhhh....the power of software.

TK

 

[knotflying]

Well, Then there is the philosophical aspect. We usually cruise between 6.5 to 8.5 kts. This gives us 3 nautical miles per gallon of fuel an we can smell the roses along the way. Will more horsepower make a difference?

 

[tlkenyon]

Yup...we also usually travel at 1400 rpm which is about 7 mph and about 6 mpg...being more about the journey than the destination The OP opens with "Just wondering," but I sure coulda used the extra oomph passing that tow...''

Thanks everyone for the interesting discussion...

TK

 

[Scuffy]

Just wondering what your boats current top speed is and what is maximum rpm for your current 150 hp engine?

 

[tlkenyon]

Top speed of just shy of 20 mph @ 3000 rpm.

 

[Levitation]

And just one last thought - if you are able to make the hull go faster, bow rise and lateral control become real issues. The shape of the hull is not designed for much above 20.
You want to go like a cigarette boat, get a Donzi or such :mrgreen:
Also, as an old engine guy - when you start hot rodding engines be prepared for expensive failures. Throwing a rod out through the block was a routine occurrence for us while testing transmissions to destruction. We would just shrug and make a phone call to Flint and later that day a truck would deliver another couple of engines.
Easy when it is not your money. Harder when it is.

 

[tlkenyon]

Was thinking more along the lines of 25 or so. My brother (the motor-head) has a 600 hp jet boat....scares the you-know-what out of me....