Inconsistent planing help

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Jerry_W

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I have a 1999 24' Sea Ray with sterndrive Mercuiser. In one recent trip with 3 other passengers I had problems getting the boat on to the plane at all. I put this down to having passengers sat right at the back.

Next time out was only one other passenger, the boat seemed to get on the plane quite comfortably and motored along quite happily at around 22knots, 3500 rpm.

Last time out, again only one other passenger but boat stuggled again. At around 3500 rpm I could only get to 12 or 13 knots. Increasing to around 4000 rpm only seemed to labour the engine with little or no extra speed. I tried trimming with the drive and trim tabs. I could feel they were operating, but didn't help at all. This was coming out of Poole, with the tide and little or no wind, for once!

When I anchored , I looked and there didn't seem to be much weed on the drive or trim tabs.

The above points I have mentioned based on factors others have suggested in similar threads. I wondered if anyone had any thoughts about what might be the cause of the inconsistency. I would be quite comfortable if the answer was me!
 
Jerry_W said:
I have a 1999 24' Sea Ray with sterndrive Mercuiser. In one recent trip with 3 other passengers I had problems getting the boat on to the plane at all. I put this down to having passengers sat right at the back.

Next time out was only one other passenger, the boat seemed to get on the plane quite comfortably and motored along quite happily at around 22knots, 3500 rpm.

Last time out, again only one other passenger but boat stuggled again. At around 3500 rpm I could only get to 12 or 13 knots. Increasing to around 4000 rpm only seemed to labour the engine with little or no extra speed. I tried trimming with the drive and trim tabs. I could feel they were operating, but didn't help at all. This was coming out of Poole, with the tide and little or no wind, for once!

When I anchored , I looked and there didn't seem to be much weed on the drive or trim tabs.

The above points I have mentioned based on factors others have suggested in similar threads. I wondered if anyone had any thoughts about what might be the cause of the inconsistency. I would be quite comfortable if the answer was me!
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You haven’t mentioned what engine the boat has.

If it’s a V8 motor, then something is wrong. The V8 should be able to put you on the plane no matter what.
If it’s a V6 then it sounds about right, Only sufficient power to get on the plane when boat is lightly loaded and sea conditions are right.
 
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You have a sea ray 240 da?
I have a 2000 model with the 5.0efi V8 and Bravo 3 leg
Getting on the plane with four onboard should not be a problem, even if all sat at the back.
22knots at 3500rpm does not sound too far off.
Struggling with only two onboard tells you something wrong for sure.
First check for weed on hull as well as legs as jrudge says. But if you went in clean and antifouled in Poole (where we are) at the start of the season it should not be bad enough to cause your symptoms.
Also check for damaged prop.
You do not say if this has developed suddenly or gradually.
If hull clean and props ok then engine is down on power.
I would start by starting it in the dark and checking the plug leads for flashes of light. Old leads can crack and earth to the engine giving a light show. Less spark at the plug = less power.
After that a compression test on the cylinders would be my next move. Low compression = low power.
 
Thanks all for your swift and helpful thoughts. There are certainly some things there I can get on and check. It is a 240 DA with 5.0Efi V8 and an Alpha One drive. The boat was out of the water for a while over the winter, when it was anti-fouled and the drive serviced.

The boat stays in the water at Cobbs Quay and weed does accumulate on the drive particularly, quite quickly. My checks for weed were from onboard and that seems the thing I should be checking most. I can try the leads though.

I think what is confusing me most is the inconsistency.

Thanks again, enjoy and stay safe.
 
Make sure the prop is clean. Even fairly minor prop fouling seems to make a big difference to my (fairly similar) boat.
 
Is this a change in performance or has the boat always been like it?
Does the drive leg trim fully down? Can this be visually checked? Does the note of the trim pump change once leg is fully trimmed in or down.
It is not unknown for the rubber bush in the prop to be slipping at high load but light load will grip
 
Hi
With this boat and other similar US boats.
It’s often the fault of the design. The big fuel tank and everything else is at the very rear of the boat just in front of the engine. Add some passengers (of course also at the rear) and they can struggle a little.
That said. Usually a well suited prop and tabs help with this. Many have changed to the big 16x16” prop to help get her up and going with this size of engine and alpha drive.

The other main suspect is as already mentioned. You have a spun hub kit. This would certainly show an inconsistency in planing performance. Either way. Look at the prop and hub.
Do you know what state your prop is in and what style and pitch it is ? A good prop can transform a boat. The single biggest difference one can easily make to the all round performance of a boat. No question.
 
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