Engine height set up on a platey

[ben_460]

I recently bought a 2nd hand plate boat and am in the process to see if it's set up right and if I can fine tune it

Current set up is

Solas 13 1/4 x 17 SS prop 3 blade
Has hydrofoil fitted
Engine mounted in hole 3 from top
AV plate lines up with bottom of hull
AV plate does appear to be buried when on the plane tho, should I expect the rpm to come up much lifting one hole ?

Full loaded with 3 punters, fuel and gear across he bay in flat conditions im getting 5100rpm WOT @ 52kmhr ( 5300-6300 WOT range in manual Honda BF90 )

Is it normally best to set the engine height then change the prop or try a lower pitch prop as is now ?











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[PROS]

what brand/size boat?

[ben_460]

AMM 5.5m cuddy


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[ben_460]

https://vimeo.com/192585781


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[Noelm]

Very much trial and error, but engine height is the first thing to get right.

[scottar]

Costs nothing to try it apart from a bit of time and a bit of sealant.

[Spaniard_King]

The engine is over propped, you need to be getting 5800 minimum for that engine to perform on that hull

[ben_460]

Ok, cheers

I'll trial a 15p prop and see where that gets me, the Solas guys said they can exchange if I need to go lower.

The Stella 15p SS was recommended to start with




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[Lovey80]

I'd lift it one hole first and see if you get cavitation then look at your RPM's if it doesn't cavitate. Gary?

[Noelm]

If the cav plate is below the water when on the plane, and it has a foil fitted, it will be causing a lot of drag, might be best to lift the motor in stages to see if RPM comes up, or cavitation starts, your max RPM is way low, and may well be over propped, but best to fix the height first.

[Chris Tucker]

the existing engine setup feels like they were trying to fix a ride issue. Before you get too busy playing around with engine heights etc how does the boat handle? Can you get the bow where you need it for the conditions? any tendency to porpoise or broach?

[ben_460]

We I'm not really in tune with it yet , had 4m tinnies before this and only done a couple of trips that were fairly flat conditions .

It does sorta feel bow high but can be trimmed down when going into chop etc easy enough

I did experience some cavitation the first trip before I replaced the faulty trim gauge but that may have just been me

On the new trim gauge the sweet spot in flat conditions has the needle down pretty low if that means anything ?


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[Chris Tucker]

A boat with the engine too low will have a tendency to run bow high and the foil is probably whats allowing you to correct that. People do all sorts of things to the backs of boat based upon advice from mates and the expert at the local pub. Before you spend any money at all go back to scratch and work you're way back into the setup.

1. remove the foil. What happens?
2. raise the motor a hole? Does the cav plate dry out? What happens to the ride and performance, RPM etc?
3. if performance is better but it starts to do funny things put the foil back on. Now what happens?

[ben_460]

Sounds like a plan of attack


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