cruisecraft reef ranger porposing problem

[Casey Ison]

Yeah Giday Fellas, first up new to this forum do read lots here but first time posting!

I have a crusiecraft reef ranger I fully restored this boat from trailer to roof, and when I did so I put a solid 70 mm transome in new floor stringers and attached an alloy hardtop and pod.

I have been using the boat for about a year now and I have found it does porpose in calm conditions unless the donk is completely trimmed down. Also it seems to jump off the smallest of waves a tad more. When I designed the pod I made the pod to the shape of the boat and it has 3 air tanks for bouyency. I figured this would help with the motor being back a bit further on the boat. I put the cav on the motor roughly level with the bottom of the boat. The boat handles perfectly with the pod, steers just as good if not better then before I did all the work but yeah just this porposing problem.

I have been doing some reading and people have suggested to others with this problem to lift the motor higher?

Any ideas muchly appreciated willing to give anything a go otherwise ill be running in trimmed fully down.

Cheers in Advance

[Jarrah Jack]

Nice looking boat, well done. Some pics of the pod and motor might help. The cheapest and easiest thing to do is to raise the motor. What hole is it set at now? You may need a jacking plate. Does the boat have tabs?

[Moonlighter]

Generally, if the engine is set too low, it can contribute to porpoising. If that is the problem, lifting it usually helps quite significantly.

When you are cruising at say 4800 rom, where is the cav plate on the engine? You should be ale to see it skimming the surface, not under water. If its under water, lift engine until its skimming when engine trimmed halfway.

The other issue is weight distribution. Not to much weight aft?

[mull dog]

Try a foil

[Casey Ison]

yeah I did set up the motor exactly how it was when it was on the well. Me and the old boy did our sums and worked out exactly where it use to sit only thing is maybe because its further back. yeah well to much weight aft shouldn't be a problem I wouldn't think as the boat sits nicely in the water because of the pod air tanks add quiet a bit of buoyancy.
I honestly haven't checked the cav plate at 4800 rpm. but I do know I cannot trim the motor up at all it has to be fully down or it will porpoise straight up..

the boat already has a foil on it.


edit also the motor is in the 2nd lowest hole so I think ill have a crack at lifting it and see how it goes?

[Shark Poker]

You made structural and other changes to the hull, mate.
Now you need to treat it like a custom rig and review motor height, props and more props, possible foil, you name it.
But don't see it as a chore, its all just positive fine tuning.
Happy improving!
Pauly

[peterbo3]

Can you take it for a run fully loaded on a flat track. Get it up on the plane & with your mate driving check out the position of the anti ventilation (cav) plate on the leg. It should just skim the surface. If it is under water by any more than a few MM your engine needs to come up. If the plate is out of the water (unlikely) it needs to go down. Adding the pod & solid transom has changed the centre of gravity which will change how the hull sits in the water. Is the pod full width? A half pod can really cause problems as it does not have the buoyancy to support the engine & the stern will sit lower.

[Casey Ison]

Can you take it for a run fully loaded on a flat track. Get it up on the plane & with your mate driving check out the position of the anti ventilation (cav) plate on the leg. It should just skim the surface. If it is under water by any more than a few MM your engine needs to come up. If the plate is out of the water (unlikely) it needs to go down. Adding the pod & solid transom has changed the centre of gravity which will change how the hull sits in the water. Is the pod full width? A half pod can really cause problems as it does not have the buoyancy to support the engine & the stern will sit lower.

Yeah mate I can do this down tin can, and yeah I will definitely lift it and give it a go im sure its not to low. the pod is not a half job its full width of the boat and follows the shape of the boat.. im not a fan of those half pods have seen a lot of boats screwed steering wise and ride wise with box pods... I will get some pics of it and upload sometime. cheers

[STUIE63]

Take the foil off and play with the engine height as others have suggested once the engine height is right then have a play with props and make sure your motor is getting max revs. Then if the boat needs it try the foil again

[Casey Ison]

Take the foil off and play with the engine height as others have suggested once the engine height is right then have a play with props and make sure your motor is getting max revs. Then if the boat needs it try the foil again

yeah no worries I will give this a crack might even take a few tools down to the bay with me and take it for a run and see and readjust at the block to save towing it all the way home and back again for a 10 minute height adjustment.

cheers for all the help appreciate it.

[Horse]

I think that model will do better with a foil. I would also look at a transom wedge if you followed the original hull configuration when you rebuilt. As the others suggested look at raising the motor. I would be surprised if you cant go two holes if you keep the foil on it

[deckie]

You've done a great job with the mods. Looks so true to its lines. Teething problems matey...so much of a major change to the initial hull with pods and weight changes it would have been a fluke to get it spot on first up.
Hopefully for you its a simple matter of engine height as others suggest.
Just one question that might help with things to try first rather than last...hard turns..getting any prop vent/cav during fast hard turning in current configuration, or before u put that foil on ?

[WalrusLike]

It's easy to be fooled by a picture but that prop looks low to me...

Using a iPhone and my hand flat at right angles to it.... I have done a series of exhaustive simulations and experiments.

So now I am back from the laboratory and can report that a lower motor will increase the turning moment about the centre point and hence contribute to porpoising.

Of course.... it is possible that my wife is correct and that I am just a doddering idiot waving his phone around in the air.....

Good luck with it... the boat looks sweet.


(Using Tapatalk on iPhone so can't easily 'thank' or 'like')

[Jarrah Jack]

There's been a lot of talk about the foil. They should be a last option on any sea boat. After speaking to Murf about his problems with the foils steering the boat while going down hill with breaking waves I wouldn't go near them.

I can imagine that the motor may have to go up higher than the two holes left which is why I suggested the possibility of a jacking plate. The motor looks a two stroke so shouldn't be a weight problem. Unless its a full width pod following the hull lines the rule of thumb is to go up 1 inch for every foot of the pod from the transom.

Once the engine is setup right I would recommend tabs after trying them out for the first time on my boat in some rough water. They can totally transform the ride of a deep v boat and have no negative characteristics like a foil.

[stue2]

seen this before with very similar mods. is the pod level with the hull or higher? The boat I know of was fixed with trim tabs and raising the motor much higher. As the water is released from the hull it rises so the motor will need to be higher than you think also the running angle will be slightly different dropping the motor in a bit more. once this was all sorted the boat I speak of was a gem.

nice work