Hi Darby ,

It is not a time consuming task to check the ballance of a prop - 10

minutes at the most - the prop shop may do it for you for free if you ask  -
you would then know if your prop is unballanced  and have some estimate of
how much unballanced it might be - my local prop shop will allow you to
witness this simple process - but not all shops do .

Another sometimes helpful quick and dirty rough indication might be to

run the numbers of the prop selection formula - or to use the prop selection
program on the Michigan Wheel  web page  ..... see what prop size that Mich
recomends ... You can use various hp estimations from your engine RPM - HP
graft to play with this a little  - 15 to 20 minutes  with the Michigan
page may give you quite a bit of information .

Recalling that the porp slip at these speeds will approach 50 % - it is

a little difficult to imagine that a minor change in either prop size or
pitch will provide very much improvement .  A four blade may give somewhat
less vibration but also less - not more speed at the same RPM - but your
present prop should not kick up a fuss from vibration  - a the speed of
shaft speed of only  900 or so .

If the prop size and pitch are in the ballpark and it is ballanced - or

not unresonably out of ballance - you might check the shaft alignment ,
stern bearing , stuffing box
packing .. and especially the security of the engine mounts to the stringers
and the engine mounts themselves .

 At a low shaft speed  I would be looking for other problems in the

driveline - unless the prop were shown to be absolutely out of whack .

Do  the easy  and  cheapest  checks first .

Will be of interest to follow your progress.

All the Best
Ken
m/v Mrs. Hudson

My mistake - shaft speed would be in the range of 600 not 900 .
Ken

Drats - I just checked the Michigan Wheel page - you cannot play with it
any more -- someone else may know of a computer selection chart on line -
but I could not find one in a few minutes of searching ..

Ken

We have a question that we would be interested in solutions to:

Our 35' trawler is powered by a 135 hp Ford Senator engine (same as Lehman)
Transmission is 3:1 Newage
Prop is 3 blade 27x23.5 (changed by PO from 28x?)
Engine maxs out at 2400 under load, 2650 with no load.
We run at about 1800 and get 6 knots

Mike feels the boat should get 8 knots.  We have looked up similar boats
with similar engines and that is what they are getting.

Engine people say engine is fine, but would replace transmission with a
2.1:1 velvadrive which is what they usually use.  They say the 3:1 would be
good for hauling traps etc. giving extra pulling power but reduced speed.

Transmission people say transmission is fine, but engine should turn at 3000
with no load, and so before replacing the transmission they say we should
look at having the engine checked.  Engine people say 2600 is good and
engine won't do 3000.

Prop guy says engine and transmission OK as is and he can get us the better
speeds by changing the prop.

The reason all this got started is because we heard a rumbling noise at the
stern.  Had engine guy on board and he says no imbalance in the engine/drive
train but suggested having the prop pulled and balanced.  So we pulled the
prop and took it to the shop where it was made and prop guy said a smaller 4
blade would be better.

So, the prop still sits in the shop untouched waiting for us to decide
exactly what is needed.

We called previous owner who says he got all the parts from another boat.

Any suggestions?

Thanks,
Darby