Cutlass Bearing 38
Happy New Year Professor
Searched previous threads for help and read it may be possible to remove the propshaft by unpacking the stern gland and wiggling it. My engineer inferred only way was engine out and remove propshaft. If this is the case I might replace the Bukh 24 with a more powerful, lighter engine.
Can you advise on Cutlass replacement options (I only do 40 hours a year), and engine choices.
Thankyou
Alasdair
Billyon

Dear Alasdair
Suggest you first try by using the maximum opposite shaft deviations in the stern tube and strut sleeve. If this does not work the shaft strut could be loosened somewhat, it is bolted through the hull with a few bolts.
Before installing more power I would like to ask which type of propeller and number of blades, max speed and rpm at full throttle?
Kind regards
Lars

Thankyou, am not near boat to look, are the bolts commonly glassed in , or easily accessible? Maxprop17" 20 degree pitch (3 blade) Had problems with engine smoking and tried various settings for speed /torque/propkick, this was best compromise. Max speed 6.5 @2800, but loads of smoke, so generally do 6 @ 2200. Clearance of blade <1 cm, possible cavitation? - had considered taking 5mm off tips but was advised by Darglow not to. Alasdair

Dear Alasdair
Thank you for the information.
The strut bolts are glassed in.
The engine needs to achieve 3600 rpm in order to develop the nominal 24 hp, but the recommendation is to reduce the pitch to 18 degrees, this will increase max rpm to abt 3100, and this is a good compromise. Has the fuel injection system been checked? The smoke suggests it is not working properly.
The top speed should be 7 knots, and Bukh is a heavy duty fishing boat engine, you should be able to use that speed all day if you like to.
If the small propeller clearance causes noise it could be considered to carve off a little from the skeg around the critical point. Depending on the amount removed some glassing could be added on the inside.
Kind regards
Lars

Thankyou
Injectors fuel etc all checked and engine regularly serviced- its been an ongoing mystery why it smokes and has no grunt. What prop tip clearance would you advise if the skeg were to be pared away (is that safe ??)
If I was to replace the engine, which would you favour ?
Alasdair

Dear Alasdair,

if you follow Lars's instruction you will see the prop shaft will be removed without any problem, and you wont have to removing the shaft strut.

I had an original Bukh (now a lighter Yanmar 29 HP) and removed the shaft with Lars' procedure more than once

Fair winds!

matteo (38/067 Only You)

Thankyou for that Matteo
Will we see you at Europeans in Cowes this July- welcome onboard if you are without boat
Alasdair

Dear Alasdair
Your reported max rpm/pitch confirms that the engine does not perform according to specifications.
Are bottom and propeller clean?
Does the engine get enough air - has it been tried with engine box open?
Another possibility is that the exhaust is blocked, or has sharp bends resulting in too much back pressure. What size and type of waterlock and where located? Has the exhaust the same diameter over the entire length?
The recommended tip clearance is 15% of the diameter - 2.5" - but unless there is noise and vibration increased clearance is unlikely to bring propulsion improvement. Add laminate on the inside to retain same hull thickness in the area.
Kind regards
Lars

Thankyou Lars
Will investigate all your points
Alasdair