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  1. #46

    Re: How high to lift the motor

    I have a related issue with a new 150 4 banger on an old hull...the cav plate level is ok but the extra weight of the motor on the pod pulls the hull down at rest and low speeds.

    just a couple of thoughts on reading through the posts...extending the pod shouldnt change the relationship between the hull and the motor except that at rest and low speed the stern will sit higher..with the extra buoyancy.. ie...If the cav plate is too low at speed now ..it will still be too low..in fact maybe a little worse?, as the extension should follow the hull line up.

    Your existing pod seems to extend back a long way..hard to estimate...but quite a lot of leverage there.I think about 600mm is the max recommended for an unsupported pod on my hull.

    I know its a little crude..but I took a couple of 25Litre black plastic drums and strapped them under the hull at the stern to see where the hull would rest if I increased the buoyancy ....and yes 50-70 litres extra buoyancy makes a big difference.

    In your case I reckon working out cheap ways to trial where you might go to solve your issues will be better than deciding A or B at the start...you may end up looking at both improving buoyancy and raising the motor a little....

    anyway just some thoughts ...good luck!

  2. #47

    Re: How high to lift the motor

    Quote Originally Posted by inveratta View Post
    I have a related issue with a new 150 4 banger on an old hull...the cav plate level is ok but the extra weight of the motor on the pod pulls the hull down at rest and low speeds.

    just a couple of thoughts on reading through the posts...extending the pod shouldnt change the relationship between the hull and the motor except that at rest and low speed the stern will sit higher..with the extra buoyancy.. ie...If the cav plate is too low at speed now ..it will still be too low..in fact maybe a little worse?, as the extension should follow the hull line up.

    Your existing pod seems to extend back a long way..hard to estimate...but quite a lot of leverage there.I think about 600mm is the max recommended for an unsupported pod on my hull.

    I know its a little crude..but I took a couple of 25Litre black plastic drums and strapped them under the hull at the stern to see where the hull would rest if I increased the buoyancy ....and yes 50-70 litres extra buoyancy makes a big difference.

    In your case I reckon working out cheap ways to trial where you might go to solve your issues will be better than deciding A or B at the start...you may end up looking at both improving buoyancy and raising the motor a little....

    anyway just some thoughts ...good luck!
    Inveratta, Adding to the bottom of the pod was an option, Al from Seatrek Marine offered to build a temporary plug for it to trial, it all seems to be trial and error, I think this would work but ideally I would have a preference to lift the motor higher.

  3. #48

    Re: How high to lift the motor

    Quote Originally Posted by Dignity View Post
    Fed, you're asking me to remember something from 4 years or more ago, I can't remember yesterday. To be honest I know that the old motor didn't seem to get as buried as this one and I have no idea of the shaft length, I do recall that I didn't have as many problems with the skeg hitting the ramp with the old 2 stroker so maybe I might investigate the conversion back to a 20 inch shaft although the higher I can get the motor above the water the happier I will be, including my mechanic.
    this is a relatively easy job. I had my 25" Mercury shortened down to 20". Cost me $100 on top of the purchase price to shorten the drive shaft (and machine a new spline), gear selector rod and water tube.

  4. #49

    Re: How high to lift the motor

    Shortening the motor is probably the least preferred option, it will get the motor height right, but the power head will be low in the water, remember, you have added weight with the 4 stroke, making the stern heavy.

  5. #50

    Re: How high to lift the motor

    Been talking to a few people and the whole issue is an absolute minefield. The anti cav plate is definitely too deep, the motor too close to the water. Building a plate to raise the motor is feasible but with a pod 730mm long I thought the leverage was quite high. A solution I'm leaning towards is to build a new pod around 600mm long but to have it as an extension of the hull. Now the overall width is 600 mm which should give me additional buoyancy but how much.

    My calcs say it should provide about 80 kg lift but is this correct, I think there are a couple of things I've probably got wrong remembering the current pod is 230 mm above the bottom of the hull, and I'm not sure this will solve my problem.

  6. #51
    Ausfish Bronze Member Marchy001's Avatar
    Join Date
    Oct 2010
    Location
    Ipswich

    Re: How high to lift the motor

    Does the boat have an excessively bum heavy feel in general?

    On my Seafarer when I installed the 225 4 stroke it was very bum heavy so I pulled out the 3" jack plate to see if that helped. Didn't change the arse heavy feel at all but having the motor around 3" lower in the water changed the handling for the worse quite noticeably. So much so that I put the jack plate back in after 1 trip.

    I don't know the maths behind it but I wouldn't expect the leverage difference between the 730mm pod and 800mm pod + jack plate to be much at all?

    I'm guessing a new arse end will be up around or over a grand. A jack plate couple of hundred and will allow you to change things around easily. If you still want to go the pod option after trying the jack plate gumtree will probably return you 80-90% of the cash for your jack plate and then go for a pod with more data to get it right the first time.

  7. #52

    Re: How high to lift the motor

    Quote Originally Posted by Marchy001 View Post
    Does the boat have an excessively bum heavy feel in general?

    On my Seafarer when I installed the 225 4 stroke it was very bum heavy so I pulled out the 3" jack plate to see if that helped. Didn't change the arse heavy feel at all but having the motor around 3" lower in the water changed the handling for the worse quite noticeably. So much so that I put the jack plate back in after 1 trip.

    I don't know the maths behind it but I wouldn't expect the leverage difference between the 730mm pod and 800mm pod + jack plate to be much at all?

    I'm guessing a new arse end will be up around or over a grand. A jack plate couple of hundred and will allow you to change things around easily. If you still want to go the pod option after trying the jack plate gumtree will probably return you 80-90% of the cash for your jack plate and then go for a pod with more data to get it right the first time.
    It's bum heavy as the 4 stroke is about 35 to 40 kg heavier than the old 2 stroker. I think the exercise would have been easier if the pod was level with the bottom of the hull but with the pod being 235 mm higher it confuses everything. Adding 3 inches or so with a Jacking plate would possibly make it worse as the prop would be in dirtier water. I figure bringing the motor closer, increasing buoyancy should raise the motor and having cleaner water over the prop can only help.

    800mm pod sounds rather long.

  8. #53
    Ausfish Bronze Member 552Evo's Avatar
    Join Date
    Jul 2016
    Location
    Melbourne

    How high to lift the motor

    Dignity, thinking about the last two replies - how and extra 30- 40 odd kilos changes the dynamics, so would anyone, say an adult (80 odd kilos) standing at the stern make the same change ?
    I'm just saying that because with anyone standing at the stern of my boat it wouldn't make all that much difference ??


    Saltwater fishing, boat mad but has a job that gets in the way.

  9. #54
    Ausfish Bronze Member Marchy001's Avatar
    Join Date
    Oct 2010
    Location
    Ipswich

    Re: How high to lift the motor

    Quote Originally Posted by Dignity View Post
    I figure bringing the motor closer, increasing buoyancy should raise the motor and having cleaner water over the prop can only help.

    800mm pod sounds rather long.
    Everything I've read regarding jack plates engine placement etc is the further away from hull the cleaner the water is that runs through the prop and the higher you can mount the engine. Bringing the motor closer to the planing surface will in effect raise the propeller in relation to the waterline at speed yes. Increasing buoyancy will carry the weight of the motor better. Changing the planing surface for my mind opens up a whole world of variables. You would need to ensure the planing surface remains flat the whole way to the transom or it could effect the handling of the boat. I'm sure your boat man mentioned this already however.

  10. #55

    Re: How high to lift the motor

    My pod maker can't get around to making it till after Xmas so I have some time to play around. I'll be making a mould for a temporary extension bolted to the existing pod to trial the mods, this will give me a chance to see if this solution is heading in the right direction.

  11. #56

    Re: How high to lift the motor

    I'm an old boatbuilder who has probably forgotten more than I learnt.

    In my opinion you are as already said opening up more problems by extending.

    I believe and my opinion only is one of two things

    1. Replace motor with correct height motor (yes it is an added expense you didn't want)

    2. Get that motor shortened.


    Sent from my iPhone using Ausfish forums

  12. #57

    Re: How high to lift the motor

    Quote Originally Posted by shakey55 View Post
    I'm an old boatbuilder who has probably forgotten more than I learnt.

    In my opinion you are as already said opening up more problems by extending.

    I believe and my opinion only is one of two things

    1. Replace motor with correct height motor (yes it is an added expense you didn't want)

    2. Get that motor shortened.


    Sent from my iPhone using Ausfish forums
    Thanks Shakey, both of the above only solves one of my problems, the other is that the motor head is too close to the water line, in calm seas it is ok but in rough or following seas the motor gets a bathing. Therefore a more complex solution is required, initially raising the motor with an alum plate to see if that helps, making a temporary filling under the existing pod which has stress fractures which would need repair anyway.

    Depending on outcomes I would either then repair the pod and leave the plate in place or make a new pod which extends to the hull bottom.

  13. #58

    Re: How high to lift the motor

    The way I see it, new pod full width inline with hull and shorter.


  14. #59

    Re: How high to lift the motor

    Quote Originally Posted by Gon Fishun View Post
    The way I see it, new pod full width inline with hull and shorter.
    Hadn't thought of going full width, might explore that option.

  15. #60

    Re: How high to lift the motor

    Quote Originally Posted by 552Evo View Post
    Dignity, thinking about the last two replies - how and extra 30- 40 odd kilos changes the dynamics, so would anyone, say an adult (80 odd kilos) standing at the stern make the same change ?
    I'm just saying that because with anyone standing at the stern of my boat it wouldn't make all that much difference ??


    Saltwater fishing, boat mad but has a job that gets in the way.
    EVO, move that out 700mm + beyond the transom, I'm not a mathematician but I suspect the increased leverage would make a difference.

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