Runing in a new engine - Page 2

Daniel TD5 · 28 April 2004, 12:43

well thats me sorted
have kept it very easy for the first five hours with varying use of the power
took it back to the dealer for a refund

only jokeing had a fuel leak
the engineer came out from the shop in the pouring rain and changed the engine and fuel line conectors in 10 mins and said sorry sir what a service
i asked about running in again he said the first five hour are the one s to watch out for the next five still take it easy buy try full speed of sort bursts

about the trim pin as you say its to cover them selfs for you damaging it but that what the pin is for ???

like landrover who got sued from a owner that put a landrover roof rack on with
a ton of stuff on it and then went off roading landrover ended up side down
the owner said it did not say in the owners hand book that i could not do that
he won lots of money

Mark Halliday · 28 April 2004, 13:04

Got to be up.
If you tow with the engine down the G of G of the engine is well behind the transom so any bouncing of the boat & trailer will put the top fixing bolts under tension and be trying to pull them out.
Engine up and the CoG will be over or closer to the transom and the fixings will be in shear and the force will be carried down the transom.
Hydraulic PTT will not alow the engine to bounce around the pivot. Hydraulic oil is not compressable and will effectivly lock the engine in any position that it is left. I guess the lock is to stop the engine dropping if a cylinder or valve fails.
Well, thats the sort of thing my A level physics teacher tried to tell me.

If you do not have PTT then the engine will bounce around like a very bouncy thing unless you tie it against a stop.
Also, if the engine is down, you stand a chance of grounding the skeg on any bumps, dips, ramps or sleeping policemen you cross. Been there, and done that and got the scraches.

Cookee · 28 April 2004, 18:12

Quote:

Originally Posted by Mark Halliday

Got to be up.
If you tow with the engine down the G of G of the engine is well behind the transom so any bouncing of the boat & trailer will put the top fixing bolts under tension and be trying to pull them out.

Hate to disagree but surely that is exactly what the engine is trying to do whilst underway, and even the best skipper might get airborne occasionally and be a bit enthusiastic on the throttle - I would certainly not expect the engine to pull bolts out of a properly built transom and a correctly mounted engine!

We tow with the engine right down on the race boat as do all others - as there is no choice with a short shaft XR2 - it only has trim and no tilt!

When towing a conventional trim and tilt engine I always power down onto the built in support - not saying it's the right way but my way!

Tim M · 28 April 2004, 18:35

We've been here before on RIBnet. I seem to remember the general consensus being that it's best to tow your engine in the down position as it puts less leverage on the top of the transform when you go over a bump.
However, my engine is too long. I normally tow it up with the power trim holding it in place, as low as I can get away with (about 20 degrees from the transform.)

Red Fox · 28 April 2004, 20:52

I think we need one of those American jobbies so that we can power down onto it and tow with the engine as low as we dare. However, I dont want to risk it without some stopper of some sort so until then, I'll keep it up!

How about a rubber roller, they come with the hole through, and cut out a section so they fit around the hydraulic shaft, a quick release plastic tie to stop it falling off, power down and away you go...now where is the Towshure magazine...page 229 item 23...side roller, solid rubber 20cm long with 16mm hole and 58mm diameter...£4.95+p&p. Cut it to the length you need and voila! What do you think?

Hell...£4.95 delivery...OK next time I visit a boat store, unless you know a trailer manufacturer that will post it out for less...but don't tell em what it is for otherwise they will charge $30 like the yanks!

Mark Halliday · 28 April 2004, 22:44

Quote:

Originally Posted by Cookee

Hate to disagree but surely that is exactly what the engine is trying to do whilst underway, and even the best skipper might get airborne occasionally and be a bit enthusiastic on the throttle - I would certainly not expect the engine to pull bolts out of a properly built transom and a correctly mounted engine!

Cookee
Disagree away, it's what the forum is all about.
But first try this.
Find a chair with a back. Turn it upside down. Curse because the seat fell on your toe.
Hold the chair back just below the seat, legs straight up, front away from you and grip with your thumbs pointing up. You will feel a force pushing on the lower part of your palm and pulling on you fingers. Bounce the chair up and down and feel how it reacts. Your wrists will be doing the work.
Now tilt the chair so that the top of the front legs are above your hands and repeat the bouncing. Tip it back some more and bounce again. Is there less force trying to bend your wrists?
Now imagine the legs are the power head, the back is the engine leg, your wrists are the mountings and your forearms are the transom. Is it starting to make sense?

No..........?

Well just think what the neighbors were thinking when they looked in you window just now.

Matt · 28 April 2004, 23:02

You're talking about big moments aren't you?

Quote:

Originally Posted by Mark Halliday

Cookee
Disagree away, it's what the forum is all about.
But first try this.
Find a chair with a back. Turn it upside down. Curse because the seat fell on your toe.
Hold the chair back just below the seat, legs straight up, front away from you and grip with your thumbs pointing up. You will feel a force pushing on the lower part of your palm and pulling on you fingers. Bounce the chair up and down and feel how it reacts. Your wrists will be doing the work.
Now tilt the chair so that the top of the front legs are above your hands and repeat the bouncing. Tip it back some more and bounce again. Is there less force trying to bend your wrists?
Now imagine the legs are the power head, the back is the engine leg, your wrists are the mountings and your forearms are the transom. Is it starting to make sense?

No..........?

Well just think what the neighbors were thinking when they looked in you window just now.

Cookee · 29 April 2004, 09:16

Mark fair point but now imagine this - hold the chair in the "down" position and get that Wilkinson bloke who plays rugger quite well to come and kick the bottom of it!

When your 2 broken legs have healed along with your wrists you might see where I am coming from!

Mark Halliday · 29 April 2004, 09:44

Quote:

Originally Posted by Cookee

Mark fair point but now imagine this - hold the chair in the "down" position and get that Wilkinson bloke who plays rugger quite well to come and kick the bottom of it!

Gottcha.
You are now talking about the boat under way and the prop pushing you along. Yes, the thrust is trying to to pull the top bolts out and the bottom bolts onto the transom. The engine produces a progressive increase in force as you accelerate, which becomes a constant when you reach max speed for throttle setting. Hopefully the engine manufacturers have designed this into the mountings. Now imagine, God forbid, that you hit some unmoveable object with the bow, I bet the engine will try to carry on for a while.
When towing, this would be like reversing the prop into a kerb. Another reason to tow "up".
Towing a boat the engine will experience sudden impact loadings over bumps etc. not a progressive push.
Oh yeah, don't engines fall off race boats every now and again - failed mounts and so on?

Cookee · 29 April 2004, 10:10

Mark - yes it is a constant force untill you are a bit slow on the throttle when the prop leaves the water and you go from 0 to X horsepower trying to rip your engine off the back!

We have broken a couple of saddles in the past because I was trying too hard and doing the above repeatedly in conditions most sane people would not bother going out in unless they were in a lifeboat and had to rescue someone!

The point I'm trying to make is that the mounts and bolts SHOULD stand up to the forces involved in towing, and I don't understand what that bracket is for on all? outboards if it isn't for towing?

John Kennett · 29 April 2004, 11:03

Quote:

Originally Posted by Mark Halliday

The engine produces a progressive increase in force as you accelerate, which becomes a constant when you reach max speed for throttle setting.

Only if you're in a flat calm! You don't even need to be "flying" the boat to get massive changes in the load.

John

Mark Halliday · 29 April 2004, 11:23

Cookee
I have just re-read the thread and we seem to have gone a bit off topic.
The forces imposed when racing are going to be a lot more extreme than us mere mortals are likely to experience. Part of the original question was “up or down when towing”. It then went on to “what is the tilt stop for?”
I think the up and down thing is down to personal choice and circumstances. In my case the engine manual says nothing about towing! Just leaving the engine up afloat. The tilt lock is only mentioned in relation to withdrawing the trim rods. I like the more balanced up position. Engine down most defiantly grounds the skeg on bumps, and the trailer balance is set up for engine up. It makes a hell of a difference to the nose weight.
Smaller outboards without PTT seem to have lightly constructed tilt locks, which could disengage over bumps. Red Fox’s manual implies this.
Hydraulic PTT should hold the engine anywhere, that is what hydraulics do. The lock in this case, I should imagine, is a safety device in case of hydraulic failure.
I seem to have got a green button, and do not want to do a Manos, so shall we agree to be confused together?

Cookee · 29 April 2004, 11:28

Quote:

Originally Posted by Mark Halliday

I seem to have got a green button, and do not want to do a Manos, so shall we agree to be confused together?

Sounds good to me!

Mark Halliday · 29 April 2004, 11:31

Quote:

Originally Posted by John Kennett

Only if you're in a flat calm! You don't even need to be "flying" the boat to get massive changes in the load.

John

What I have failed to say is that when afloat the forces tend to be in a fore and aft direction, drag - flying, less drag - land - sudden drag with more power 'cos the revs went up when airborne. When towing the are more up and down.

I seem to be in a hole. I shall stop digging!!!!!!!!