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View Full Version : motor height set up on small cat, advice please.



catcrab
05-11-2009, 06:50 PM
Hi all, i have recently purchased a small 4.3 markham whaler centre console(waverunner) currently running twin yammie 30hp l/s,i have just purchased a set of after market CMC POWER TRIM AND TILTS for the motors, the motors will sit a further 5-6 inches off the back of the transom, the current cav plates are positioned 40mm below the hulls, my questions are, was this to low, are cats different to monos to set up, as the instructions on the CMC's say that i should be position the cav plates 1 to 3 inches (25-75mm) above the hulls, any advise would be appreciated.
Thanks Drew.

Noelm
06-11-2009, 08:24 AM
very much a trial and error thing, but they did seem a little low, if you are further back, then you may need to lift them a hole (or two)

finding_time
06-11-2009, 09:21 AM
I know it's a differant boat but the kc ones are best at 2 1/4 inches above the hulls but kc pods are longer so i would start with 2 inches and work from there!

ian

hinchy
06-11-2009, 09:40 AM
Hi all, i have recently purchased a small 4.3 markham whaler centre console(waverunner) currently running twin yammie 30hp l/s,i have just purchased a set of after market CMC POWER TRIM AND TILTS for the motors, the motors will sit a further 5-6 inches off the back of the transom, the current cav plates are positioned 40mm below the hulls, my questions are, was this to low, are cats different to monos to set up, as the instructions on the CMC's say that i should be position the cav plates 1 to 3 inches (25-75mm) above the hulls, any advise would be appreciated.
Thanks Drew.

Hi Drew

I find that on the Raider Cats [4.1mtr hull, 4.6mtr with pods]
that the outfit works really well with the cav,plate about 50mm above the bottom of the hulls.Have done a fair bit of experimenting with various heights and this seems to work best for my boats.

Kind regards

Hinchy

adam69
16-11-2009, 01:34 PM
Hinchy,

I have recently bought a Raider Cat - name is Lunasea.... quick question, it has twin 40 yamaha's 4 stroke, but i dont think there is enough trim in the motors, as i can only trim the boat out 1/3 of the total trim (if that makes sense?) the motors are on the lowest hole, and i think they need to go up 1 or 2 holes. Not sure on the measurement, but when i try to trim it out it just cavitates. cant get the hull up enough and i just think it burys...can you help out with adjustment thanks...

Noelm
16-11-2009, 02:00 PM
lifting the motors will not help in stopping your problem I would be thinking! (probably make it worse)

adam69
16-11-2009, 03:01 PM
They are mounted on the lowest hole, so by going up 2 holes would put the motors down a further 40 odd mm??? Wouldnt it?

hinchy
16-11-2009, 04:19 PM
Hinchy,

I have recently bought a Raider Cat - name is Lunasea.... quick question, it has twin 40 yamaha's 4 stroke, but i dont think there is enough trim in the motors, as i can only trim the boat out 1/3 of the total trim (if that makes sense?) the motors are on the lowest hole, and i think they need to go up 1 or 2 holes. Not sure on the measurement, but when i try to trim it out it just cavitates. cant get the hull up enough and i just think it burys...can you help out with adjustment thanks...

Hi Adam
I know the boat well.The original owner had aluminium plates fitted to the pods to raise the motors.Whilst he owned the boat it worked really well,however he did sell it on and I do not know whether the owner before you has lowered the motors from their original location.Check the cav plates,as they should ideally be approx 50mm above the bottom of the hull.
These boats are trim sensitive in flat water and you will need to find the ideal trim setting to make it feel stable at speed,keep the port motor down and incremently raise or trim the starboard motor out to achieve a balance.It takes a bit of fiddling around,however you will get the hang of it quickly.

Kind regards

hinchy

John Buoy
16-11-2009, 05:33 PM
Hi all, i have recently purchased a small 4.3 markham whaler centre console(waverunner) currently running twin yammie 30hp l/s,i have just purchased a set of after market CMC POWER TRIM AND TILTS for the motors, the motors will sit a further 5-6 inches off the back of the transom, the current cav plates are positioned 40mm below the hulls, my questions are, was this to low, are cats different to monos to set up, as the instructions on the CMC's say that i should be position the cav plates 1 to 3 inches (25-75mm) above the hulls, any advise would be appreciated.
Thanks Drew.
The earleir model Markhams in the 4.3 and 4.9mt
range all had problems with porpoising as they are heavy
ass ended boats and most are underpowered because of the weight issue.
The only real fix for them that works a treat is to fit a set of permatrims
and raise the motors to approx 30-40 mm above the hull line.
This will counter the porpoising give you more trim adjustment and heaps more
planing response.
Being twin 30's you could also get away with the cheaper foils on the market;)

Regards Frank

gavsgonefishing
16-11-2009, 06:28 PM
Mine had the original 40 mariners with no ptt. It was a dog to get up on the plane etc.
What John Bouy says is spot on, they do porpoise big time and this is very hard to fix. My guess its to do with the assymetrical hull at the back with the rounded hull at the front, a little like a sailing hull.

These things have a hard time responding to the trim and tilt, and in my experience it was quite a disappointment.

I ended up putting on two 50 fs and lifting the motors to just above the bottom of the assymetrical lower point. Any higher would cause cavitation and extremely hard steering, lower it didnt respond at all. At best I slowed the porpoising down to only the top end, and I effectively got to use half the trim.

Here is the only photo I got with the motors down, its not a real good angle but you should get the picture
Gav

John Buoy
16-11-2009, 06:50 PM
Mine had the original 40 mariners with no ptt. It was a dog to get up on the plane etc.
What John Bouy says is spot on, they do porpoise big time and this is very hard to fix. My guess its to do with the assymetrical hull at the back with the rounded hull at the front, a little like a sailing hull.

These things have a hard time responding to the trim and tilt, and in my experience it was quite a disappointment.

I ended up putting on two 50 fs and lifting the motors to just above the bottom of the assymetrical lower point. Any higher would cause cavitation and extremely hard steering, lower it didnt respond at all. At best I slowed the porpoising down to only the top end, and I effectively got to use half the trim.

Here is the only photo I got with the motors down, its not a real good angle but you should get the picture
Gav

Gav you'd be surprised what the permatrims(in lieu of foils)
would have achieved.
Biggest negative with this model is the stressing along the length
of the tunnel adjoing the sponson.
To Markhams' credit they have worked hard on the issues and resolved
the problems with the Dominators;)

Regards Frank

catcrab
17-11-2009, 12:16 AM
hi guys ,thanks for all of the replies and ideas, i have fitted the cmc power trim and tilts and at present the motors cav plates are approx 10mm above hull line and i have approx another 50mm in height adjustment, i should get a chance next weekend to put her in the water, and make the necessary adjustments and then add the permatrims if required as suggested by most responses , my boat is a 93 model and does not have that centre moulded part at the underside rear of the hull and does not have any foam in the hulls at all.
thanks Drew.

adam69
15-12-2009, 02:03 PM
How did you go mate??

catcrab
16-12-2009, 08:39 PM
hi guys , just a quick update on motor set up heights, i have set the motors up and the cav plates are approx 25mm above hull, and they ran beautifully apart from a touch of porpoising at higher revs, i will throw a set of foils on and test her again, but at this stage very happy with the set up, those after market cmc power trim and tilts, are a great product and i can recommend them for those without t & t.
thanks for all of your advise.
Drew.

lenm5
19-12-2009, 03:56 AM
Check the cav plates,as they should ideally be approx 50mm above the bottom of the hull.
These boats are trim sensitive in flat water and you will need to find the ideal trim setting to make it feel stable at speed,keep the port motor down and incremently raise or trim the starboard motor out to achieve a balance.It takes a bit of fiddling around,however you will get the hang of it quickly.


Adam,
I agree with what Hincy has suggested. 50mm above bottom of hull is a good start and trim as described. This works for me too.

Dont mess around with foils ever.

I have a Raidercat and just clocked up 300 engine hours (all offshore use running out of Tweed, Seaway and Currumbin bar). When you learn to how drive them they are very seaworthy boats for their size.

Lenny