New Suzuki 150 challenges

[Xk59D]

Here you go.

Outboard Motor Shaft Length

Do you have your receipt handy or the serial number? Can figure it out with that probably.

[brucehawsker]

Df150apx
(s/n 15003p-810670)

[brucehawsker]

Thanks Neil & Xk59D and Beamish and others. On 3rd August will be at boatyard with camera, metre rule and tape measure and will report back

[69cmw]

Originally Posted by brucehawsker

Df150apx
(s/n 15003p-810670)

X is an extra long shaft [emoji106]

[charliee]

The new motor has a shaft length of 635mm, I guess your your optic may have been a 508mm.
Not sure any amount of measuring will help if this is the case.
Maybe best to talk to the company that did the work.

[jwalker]

Bruce, the plate being referred to is the first one above the prop and its correct title is an anti-ventilation plate. Folks, wrongly refer to it as an anti-cavitation plate and then shorten that to cav plate so making it more confusing. Its purpose is to prevent air being drawn down into the propeller blades.

From your last picture, the plate looks to be about level with the bottom of the V of your hull. If this is the case, the engine should perform satisfactory. For general use, 25mm (1 inch) below the bottom of the V to 25mm above the V is a good range to be within.

There is a tendency for folk to mount outboard engines too high to achieve absolute maximum speed but it will always come with disadvantages. Primarily, ventilation in turns, poor grip in rough seas, poorer grip when the boat is heavily loaded and a markedly harsher ride when wave hopping.

You may well find that some part of the new engine is inconveniently splashing water, that's just hard luck really but you might eliminate it and still have your engine within range by adjusting the engine height up or down to either lift the offending part out of the water or lowering it to bury the offending part deeper into the water.

Do you mean the boat is lower in the water when at rest? If so, the new engine must be heavier than your Opti and you're stuck with that. If you mean the boat is travelling more bow up and so lower in the stern then the Suzuki prop is said to be 'bow lifting'. What it's actually doing is pulling the stern down. Generally this is considered to be a desirable trait because the prop is more capable of gripping the water in adverse conditions and it also assist in lifting the bow when applying throttle in following seas. However, it also makes climbing over the hump to get on plane more difficult. As you suggest, trim tabs will be a remedy for that. They will allow you to balance the boat fore and aft and will also allow you to counter listing so preventing slamming in rough conditions.

Let us know how you get on with it.

[Last Tango]

Originally Posted by jwalker

<<<There is a tendency for folk to mount outboard engines too high to achieve absolute maximum speed but it will always come with disadvantages. Primarily, ventilation in turns, poor grip in rough seas, poorer grip when the boat is heavily loaded and a markedly harsher ride when wave hopping.>>>

One inch above the keel line is not "too high" and unless you have a very badly designed boat, it's not going to "ventilate in turns" have "poor grip" or give a "harsher ride when "wave hoping" set one inch up. If anything the opposite. Lowering the bow when "wave hopping" presents the finer entry closer to the bow keeping the boat more level and reduces "slamming". A deep set prop will raise the bow and make this worse.
As Beamishkin say's, one inch above is the "starting point" and if max speed is the only criteria you're interested in you'll end up well above that.

Set 1" above keel..... From about two minutes fifty on....

https://www.youtube.com/watch?v=BJEuAdCJ_Ks

His engine is hitting the "A" frame when it's tilted! It is already visibly set too high on the transom and with his anti-ventilation plate (Cav plate) set below the keel it's too low......Sorry, this boat has been fitted with the wrong engine.

[jwalker]

Originally Posted by Last Tango

One inch above the keel line is not "too high" and unless you have a very badly designed boat, it's not going to "ventilate in turns" have "poor grip" or give a "harsher ride when "wave hoping" set one inch up. If anything the opposite. Lowering the bow when "wave hopping" presents the finer entry closer to the bow keeping the boat more level and reduces "slamming". A deep set prop will raise the bow and make this worse.
As Beamishkin say's, one inch above is the "starting point" and if max speed is the only criteria you're interested in you'll end up well above that.

Set 1" above keel..... From about two minutes fifty on....

His engine is hitting the "A" frame when it's tilted! It is already visibly set too high on the transom and with his anti-ventilation plate (Cav plate) set below the keel it's too low......Sorry, this boat has been fitted with the wrong engine.

Perhaps you need to untwist your knickers and read my post again.

[Last Tango]

Originally Posted by jwalker

Perhaps you need to untwist your knickers and read my post again.

Maybe you need to look at the photos again and check where his tilt tube is sitting with each of the engines.

50MPH is a reasonable expectation from this outfit and for that the cav plate (sorry anti-ventilation plate, not wanting to cause untold confusion) is too deep. The transom assembly is too high...his engine's hitting the "A" frame when it's tilted.
Join up the dots..............

[beamishken]

Originally Posted by jwalker

Perhaps you need to untwist your knickers and read my post again.

Last tango is exactly right
The ops origional post suggested he had an idea something was amis fitting trim tabs is covering up a fault and introducing another.
Running with tabs all the time is like running with the handbrake half on
To get the best out of the boat and engine the answer is get the set up cottect from the outset
You would only run 1" down on a heavy underpowered plodder slow boat not a 40kt+ high performance rib

[Xk59D]

I'm amazed an outboard shop fitted that engine.

Forget about trim tabs or running it 1" deeper to fix spray, there is only 1 fix and it is on phone Monday morning asking for another engine. When they mount it get them to mount it whatever 1 hole up from the "vent" plate level with keel as they clearly don't have much of a clue.

[jwalker]

At what point did I say anyone was right or wrong except for the use of the words cav plate?

Bruce posted this. Perhaps you should read it carefully.

b) more seriously, she seems to be settling in the water deeper than she did.
................
Explain to me exactly how adjusting the engine height will make the boat float higher!
-------------
Then:
Nonetheless she seems very nippy and very fast at given revs....

So his boat doesn't appear to be plodding particularly, does it?

Originally Posted by beamishken

.....
Running with tabs all the time is like running with the handbrake half on

That's just bollix.

Perhaps you should suggest to the racing boys that they remove their trim tabs to take the brakes off and they'd go faster.


Personally I think there has been substantially more to the conversation Bruce has had with the engine fitter. I'd guess a compromise has been reached regarding engine fitment and transom modification. But that's just a guess, of course.

[beamishken]

Originally Posted by Xk59D

I'm amazed an outboard shop fitted that engine.

Forget about trim tabs or running it 1" deeper to fix spray, there is only 1 fix and it is on phone Monday morning asking for another engine. When they mount it get them to mount it whatever 1 hole up from the "vent" plate level with keel as they clearly don't have much of a clue.

I think everyone bar one will agree with this !
Maybe the supplier had a good reason for supplying the wrong length engine. But I wouldnt be happy about it set up as it is and not much meat left in the transom to move up and redrill

[Xk59D]

I wouldn't accept anything but another engine to fix this, under no circumstances would I let them drill and mount it higher up.

[brucehawsker]

Thanks guys. I can't really update you as I am away till Friday. Rightly or wrongly there was no discussion with the firm which did the re-engine work. They found a suitable engine (in their view) which had good reviews and was regarded positively by local mechanics. I simply agreed to buy the engine and pay for them to rig it. On the morning before sea trial they rang me with the A frame problem. The sea trial seemed to fine. I did not run her at full throttle. She got to mid+ revs surprisingly quickly but I could not read the dial (need to fiddle with contrast!) and on GPS did 40.5kn. Opti topped out 43kn on proper two way average. Problem was lots of spray and later very limited ground clearance when in rack.

[charliee]

This maybe the pertinent point - "They found a suitable engine (in their view)". As 'they' are the experts in this case, they should take responsibility and exchange the engine for a shorter shaft.
At this point its hard for them to do anything as they don't know about the issue but ask 5 experts if its looks right and 5 will tell you it looks wrong.
I'm sure it won't be a simple or cheap exercise to get it remedied and I feel for you.

[neil.mccrirrick]

If I were you I would measure the transom and the outboard leg. Then phone the maker of the rib and ask advice re the recommended outboard. You will know what the position is at that point with a bona fide from an impartial area. That will provide you an evidence base to move forward

[Xk59D]

Bruce, have you told the dealer yet? Every day you delay plays into their hands potentially. Not sure what rules are with returning outboards or what your rights are in UK.

[Maximus]

Originally Posted by neil.mccrirrick

If I were you I would measure the transom and the outboard leg. Then phone the maker of the rib and ask advice re the recommended outboard. You will know what the position is at that point with a bona fide from an impartial area. That will provide you an evidence base to move forward

I see Things have moved on a bit since I last saw this thread..In the circumstances that sounds like good advice..
If it's really that Bad....Pity the rigger didn't do it before! ..But it's still down to him.

[brucehawsker]

Transom length is 570mm measured really carefully from bottom of the cutout to the bottom of the V.

Shaft length see earlier post by Charliee is apparently 635mm. It does look as though it is an XL.

The bottom of the cav plate is mounted pretty well exactly in line with the bottom of the V.