Propeller size

Replaced a Volvo diesel MD3B , 36HP using an ACADIA, LH, 15-10 propeller.

New(er) engine is a Universal 18 diesel, 10HP 2 Cyl.

Can I use the same propeller??

If not, what should I do?

Thanks,
Allan

 

horsepower

MD 3 B - 36 bhp 2500 rpm
Universal 18 - 14 bhp 3200 rpm
;*********************************************
;* NavCad engine file HydroComp, Inc. *
;*********************************************

[NavCad]
Version=3.00
Release=PreRelease
Date=08/15/1994
Time=10:19:16.16
Precision=6
Description=VOLVO-PENTA Md 3B 26 kw 2500 rpm light-duty 3 Cylinder

[EngUnits]
Power=Kilowatt
FuelRate=LiterPerH

[EngineLib]
RatingPwr=26
RatingRPM=2500
GearEff=1
PerfPwr=0,26,24.17,23.11,22,19.58,18.27,15.44,12.47,9.54
PerfRPM=2612.5,2500,2300,2200,2100,1900,1800,1600,1400,1200
PerfFuel=0,7.9,7.05,6.68,6.33,5.54,5.23,4.46,3.67,2.83

;*********************************************
;* NavCad engine file HydroComp, Inc. *
;*********************************************

[NavCad]
Version=3.00
Release=PreRelease
Date=05/20/1994
Time=08:58:48.81
Precision=6
Description=MEDALIST-UNIVERSAL Mdl=18 Cont. 14 bhp 3200 rpm 2 Cylinders

[EngUnits]
Power=Horsepower
FuelRate=GallonPerH

[EngineLib]
RatingPwr=14
RatingRPM=3200
GearEff=0.97
PerfPwr=0,14,13.87,13.4,12.7,11.84,10.86,9.82,8.76,6.5
PerfRPM=3300,3200,3000,2800,2600,2400,2200,2000,1800,1400
PerfFuel=0,1.01,0.85,0.72,0.61,0.54,0.47,0.44,0.40,0.39
You see the differences between two engines.
oktay çemberci

 

The question is simplified if you ran the 3B a bunch and know the cruise speed you usually get and the rpm for that speed.

If you know the fuel burn at cruise your in heaven.

With the GREAT info above all you will need to do is match the Hp , or fuel burn of the old 3B to the ones given for the new engine.

My guess is the transmission will need to be "deeper" (more reduction) and higher cruise rpm to get the same speeds.

We run a 3B and between 1600 and 1800 usually burn 3/4 gph., which is about 13 or 14 hp.

My guess is you should gear to operate at 2800 , or 3000rpm to get about the same speed and fuel burn as your used to with the smaller engine..

If the 3B had the usual 1.91 tranny at 1600-1800 engine the shaft went 800-900 rpm,or so

About a 3-1 should do with the new engine .

Plug in YOUR boats numbers ,

Have fun!

FF

 

On Propellers

Is a 18x15 3 blade "Columbia" from 1960's in good condition as just as good as a new Michigan Wheel 18x15 and 3 blade? Is the new prop so much better - like 700 dollars better that the old school one??

 

There would be ZERO noticeable difference .

However since you are going down in power , and have at least the space for a 15 inch prop, you might consider using a 2 blade instead of the 3 blade.

The prop will be more efficient and the boat will sail faster with a smaller speed brake slowing her down.

If you can hide the 2 blade behind deadwood , so much the better, for sailing!

FF

 

this is for a little trawler - dont know if it would work for a 2 blade...

 

this is for a little trawler

No problem a 2 blade will still use less fuel, and be more efficient IF it has the required diameter and blade area.

It would probably be in the 5% area , so your yearly hours would be the big concern to spending cash for a change.

Probably just installing the new engine with deeper reduction would allow the old shaft & prop to work fine.

What RPM did the old engine cruise at?

FF

 

1800-1900 rpm with the 18x15 3 blade -