Having done a bit of engine testing lately with boat idling in gear pushing against mooring I wondered if there is actually a standard of force a mooring must be able to stand.
I did a Google search but hard to find.
For example in a gale the drag force put on the mooring by a 35ft boat would be high.
Ideally I want to motor half throttle against the mooring but don't want to break it.
Any suggestions welcome.

Try a jetty.
A friend recommended running the engine hard against a jetty to give the engine work to do.

Old test was tie it to the jetty and run for an hour at WOT
If it did not overheat you are good to go

Thanks for suggestions but that assumes motor can successfully get to nearest jetty, and the jetty owner doesn't mind, and if motor fails getting back is a bigger pain (been there, done that!).
My question is not how to load test motor but how are moorings drag rated. Or is it just a guess. I can't find much on Google at all.

It's a guess, no specs, no design criteria, ditto, zip. I have seen a NZ mooring spec that came in at 2t concrete with 32mm rio with a wide base and a nice pyramidish centre. But Aussie spec, contractors guesstimate is the rule. Seabed makes a massive difference, my old mooring was on rock and I could shorten the chain and steam into it and drag the block around ( the sprays big apple bow is handy for that sort of antic ) same apparatus in grey clay, immovable, the local contractors can't lift em so now they're making them lighter

Well a 50 ton survey mooring has 2 loco wheels and a carriage wheel with 50mm stud link chain as the first riser.
In Tasmania at least.
From memory concrete block lose 1/3 of the effective weight when submerged.
Some areas in SE Qld have screw pile only mandated and engineering there has been suspect.

Select to expand quote

Trek said..
Having done a bit of engine testing lately with boat idling in gear pushing against mooring I wondered if there is actually a standard of force a mooring must be able to stand.
I did a Google search but hard to find.
For example in a gale the drag force put on the mooring by a 35ft boat would be high.
Ideally I want to motor half throttle against the mooring but don't want to break it.
Any suggestions welcome.

If the bottom is soft and you have something like a tram wheel buried, I would suggest adding 20 metres of nylon to your riser and running the engine astern. If you have room add more rope!

Select to expand quote

lydia said..
Well a 50 ton survey mooring has 2 loco wheels and a carriage wheel with 50mm stud link chain as the first riser.
In Tasmania at least.
From memory concrete block lose 1/3 of the effective weight when submerged.
Some areas in SE Qld have screw pile only mandated and engineering there has been suspect.

My mooring is a pair of carriage wheels, 4m ground chain of heavy stud link anchor chain (probably 38mm), 2m of 12mm riser chain, swivel and rope riser. Set into thick mud it has held my boat and a 50ft wayward steel cruiser in winds gusting to 55 knots. (the bastard owner and his insurance co never did pay a cent for the damage, said he couldn't afford to repair the damage to my boat, shortly thereafter he sold his freehold pub in Randwick for $30m. Still )

Whatever you do don't fall fall for the trap of fulling a tire with concrete as a mooring block.

They tend to act like flying saucers and just skid across the bottom in a blow.

Once saw three vessels on the shore, complete with their mooring tackle, all with concrete fulled tires.

Select to expand quote

nswsailor said..
Whatever you do don't fall fall for the trap of fulling a tire with concrete as a mooring block.

They tend to act like flying saucers and just skid across the bottom in a blow.

Once saw three vessels on the shore, complete with their mooring tackle, all with concrete fulled tires.

Eons ago I worked as a commercial diver and on a number of occasions went looking for these "mooring" blocks that had dragged in a blow, they appeared to roll across the bottom until the chain or swivel broke and released the boat. Always easy to find the "block", but why would you.

Select to expand quote

UncleBob said..

nswsailor said..
Whatever you do don't fall fall for the trap of fulling a tire with concrete as a mooring block.

They tend to act like flying saucers and just skid across the bottom in a blow.

Once saw three vessels on the shore, complete with their mooring tackle, all with concrete fulled tires.

Eons ago I worked as a commercial diver and on a number of occasions went looking for these "mooring" blocks that had dragged in a blow, they appeared to roll across the bottom until the chain or swivel broke and released the boat. Always easy to find the "block", but why would you.

Pretty much exactly the opposite of moorings with tram wheels. If you don't get down there with in two or three days the wheels bury and are never seen again!

Thanks again for suggestions. I will try the going astern on mooring :-)

I get it about the concrete in a tyre. Sometime ago we were anchored in thick mud and were very pleased that the anchor didn't drag at all. Until after a day or so the boat moved a bit which we didnt worry about then took off which was a worry. Pulled anchor up and found it had pulled out and was a mud ball sliding across the bottom.