Volvo 2002

[sheldon]

Hi - can anybody help - I have a Volvo 2002 fitted to my Sigma 33. At full revs in gear she is only able to do 1400rpm. Out of gear she revs easily to 3200rpm. The engine does not seem to have any power in gear. I have done a full sevice today but still no joy.

Has anyone got any ideas??

 

[jwilson]

What's round or on your prop?? Is there a lot of smoke when trying to rev in gear?

 

[MoodySabre]

Have you checked your prop - wrapped up in rope??

 

[sheldon]

Only went in the water on friday so no rope wraped round prop unless very unlucky as she was moved just a few feet to a berth by yard boat . No smoke when in gear .

 

[RobinBirch]

Check her exhaust system for delamination and consequent backpressure which chokes off the engine under load.

 

[bigwow]

Have you put a new prop on? if you have was it a larger one?

 

[sheldon]

She had a new prop shaft fitted but it all seemed to be free moving prior to launch . As for the delamination if this was the case would it not be the same out of gear as in gear.

 

[Tranona]

Check the size of your new shaft compared with the old. If the new one is 1 inch then check that the old one was not 25mm. That .4mm makes all the difference!

 

[sheldon]

Thanks for the help i was wondering if it was something to do with the shaft , I did speek to the yard about the shaft as they fit it they seem to think this is not anything to do with the problem funny that.

 

[sheldon]

I will have to speek to burnham yacht harbour again to see what they think as i cant see what else it could be .

 

[Tranona]

Suggest you measure it yourself. Borrow (or even buy!) calipers - only a few quid in B&Q, then you will know rather than relying on the yard. You can measure it just behind the gearbox coupling. also try turning by hand. It should turn freely. If it is 25mm, then it is not the problem, as even if it was supposed to be 1 inch, it will be smaller than the cutless bearing. Voice of experience having by mistake fitted a 25mm cutless with a 1inch shaft!

 

[sheldon]

Will go and measure it in the morrning .

 

[john_morris_uk]

Checking the shaft size is one idea, but if the shaft turns freely, then you need to look elsewhere. Do you know what size prop was fitted? Sigma 33's usually have a two bladed folding prop, and I am fairly confident that the shaft on our Sigma was more like 30mm than 25mm or 25.4 mm. A measure with a caliper will tell you. Furthermore the acid test is whether the shaft rotates freely by hand when the engine is out of gear.

The invoice should tell you what prop they put on, and it will give a better idea of whether it is somewhere near the right size.

 

[bigwow]

The new prop may be moving freely, but if it is too large, dia or pitch, for your engine you will get the problems you are describing.

 

[Tranona]

Hi

Suffered from a bit of brain fade last night! It is unlikely that the shaft would be larger as it would not fit the gearbox coupling nor the prop. Did they replace the cutless bearing in the P bracket? This is where I made my mistake. A 1 inch shaft goes through a 25mm bearing but not enough clearance to run freely.

 

[Chris_Robb]

Are you getting black smoke, if so you are overloading the engine - so look at shaft etc as other shave described.

If there is no smoke, then it is likely that the fuel supply is restricted. It doesn't need much to rev and engine, but run a full power, needs more fuel. So you should also check your filters.

One thing you might check, a problem I had on my boat (2003T). I had the identcal problem you describe. It turned out that the Fuel valve was turne OFF at the tank, but the engine for some reason could run by sucking out through the return. problem was sorted by turning on the fuel! I really can't understand how it could run off the fuel return.

 

[sheldon]

The shaft is new but have fitted the same two blade folding prop so dont think its the prop. The cutless bearing is also new so will check to see if it turn freely

 

[sheldon]

Hi no black smoke , Tryed changing the fuel filter , fuel valve is open . If there is a problem with the the fuel pump maybe this could be the problem then? Will call out vol spec marine enginer on monday i think to try to ge to the bottom of this .

 

[david_bagshaw]

Gas flow in the exhaust is different according to amount of load,more load more fuel burnt , more expansion of exhaust gas. As an example if the same volume of gas was produced only relative to rpm those with larger turbocharged engines would get full boost on revving up in neutral. check for delamination, crushed pipes, excess bends, corrosion at water injection point, corrosion of exhaust manifolds, then blocked fuel filter, air in fuel, blocked prefilter, failed lift pump, never mind bent blades, one blade out of pitch. etc

 

[david_bagshaw]

Did it achieve full revs before fitting the new shaft?

If so is it possible the yard altered the fold out stops if adjustable and thus alter pitch etc?

also does the engine sound to be trying to get above 1400 rpm or lightly loaded ? is the 1400rpm, tied up or underway?