Potential first sports cruiser?

[aerobat]

Hi ! Something is wrong :

with a 1.65 gearing and a 22" prop you would even with a non efficient propslip go easily north of 30 knots at true 3800 rpm and the engine would push any horse you can only expect into the water .

So :

- the displayed rpm is wrong , its not 3800 rpm ( easy to check , even hear )
- you steamed a high current river upstream ( like rhine river ) and looked at gps speed ( unprobable )
-the cone clutch is slipping !!!

If the 1.65 gearing and 22" is confirmed i would check if the drive slips , it might be its nothing wrong with the engine and it simply sits on the rev limiter

 

[ari]

Depends on the prop pitch surely?

 

[aerobat]

Depends on the prop pitch surely?

Sure , but he said its 1.65 gear and 22 pitch prop . 3800rpm and 19 knots do not match even remotely

 

[uncharted]

Hi ! Something is wrong :

with a 1.65 gearing and a 22" prop you would even with a non efficient propslip go easily north of 30 knots at true 3800 rpm and the engine would push any horse you can only expect into the water .

So :

- the displayed rpm is wrong , its not 3800 rpm ( easy to check , even hear )
- you steamed a high current river upstream ( like rhine river ) and looked at gps speed ( unprobable )
-the cone clutch is slipping !!!

If the 1.65 gearing and 22" is confirmed i would check if the drive slips , it might be its nothing wrong with the engine and it simply sits on the rev limiter

That's an interesting thought, I'd not considered. The gear ratio was confirmed on a receipt from the leg being replaced 10years ago, I'm definitely walking away from this one, given all the feedback, but, out of interest and as a point of learning, is there a way to check clutch cone slip? Put in gear could you rotate the prop by hand? Probably only shows like that if very severe I assume given the gearing effect?

 

[uncharted]

@uncharted - The boat market is dead thus meaning as a buyer you have 1000's of boats to choose from.
even if you see a boat that maybe a little out of budget a fair offer is likely to be accepted.
Don't rush for the first boat you see - go with your head not your heart.

here's a diesel for sale around 27ft For Sale 2005 Doral Monticello - Boats.co.uk

An american website selling one of these boats with this engine is claims 33 knots @ WOT.
Most of the websites with details on this 6 cylinder Yanmar are quoting 3800 at high idle.


Similar boat ?
Monterey 265 CR with Yanmar 315HP Diesel - SOLD - GulfStream Marine Boat Sales

Indeed, those gulfstream sea trial vids are a great benchmark. I watched this one before the trial to set expectations

 

[aerobat]

That's an interesting thought, I'd not considered. The gear ratio was confirmed on a receipt from the leg being replaced 10years ago, I'm definitely walking away from this one, given all the feedback, but, out of interest and as a point of learning, is there a way to check clutch cone slip? Put in gear could you rotate the prop by hand?

There are prop calculators online where you can calculate the resulting speed from a given rpm , gearing and prop pitch plus 10-15 % hydrodynamical prop slip .

If an engine revs verfied given rpms but the resulting speed is way off ( like in this case ) it cannot be anything else than the clutch is slipping or in some few applications the prop is slipping on the shaft .

Straight forward like a scenario your car engine revs 6000rpm in highest gear but your car does not go more than 100 km/h . What else than a sliping clutch ?