Issue getting on a plane with 280DA 2003 twin 4.3MPI and reach max cruising speed

Jmamacan

New Member
Apr 21, 2013
2
Sydney
Boat Info
2003 searay sundancer 280da
Engines
Twin mercruisers 4.3mpi stern drive
Hi there , i have had major issues over the years and had the boat serviced by several mechanics only to find that the best one down here in the sutherland shire cronulla in nsw australia can opnly get the boat to 14.5knots at 4200rpm.

It astounds me to find that friends of mine have 20 year old 28 foot searays that does 24 knots comfortably. Well the boat has been antifouled legs serviced and engines tuned. The computer apparently reports the engines as running at optimal performance. So what is the issue no mechanic has yet been able to resolve this for me . Some tell me it may be the gear ratio in the legs others tell me that it could be the props. Where do i start, i am not mechanically minded so hence in the hands of the gods! the mechanics.

I am told that this is the best I can get but I am not convinced. Where do i start? please help or put me in touch with someone that can help. We now only hang out local in the Port hacking river as i dont have the confidence in the boat to go outside. It travels comfortably at 8 knots but as soon as you give it some throttle it cavitates heaps of water in the stern near swim platform and all it does is chews up fuel. Drop down to 2000 rpm and runs beautifuly but only at 8 knots. Why please help!
 
My 2000 270 with the twin 4.3 will top out at 38 knots/44 mph at about 4400 rpm. I cruise at 32 mph at 3200 rpm. Usually have two adult full fuel, water and loaded for weekend trips. Your 280 should only be a couple knots slower. I have no issues getting on plane. Something is definitely wrong. I normally have tabs up and full trim down to get on plane and then trim up. If you are actually getting that rpm and those speeds you have extreme prop slippage. Do you trim full down to get on plane? Even trimmed full down and full throttle you should see 28-30 knots easy.
 
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I appreciate your inputs, and have organised to slip the boat for antifoul an will get the props removed to check pitch and diameter, but again i appreciate the assistance and prop spillage sounds like the issue, if i may ask what props do you have on your 270 as a matter of interest.
 
I have the same set up and reach 4900rmps with top speed over 49mph (very light fuel, water and gear). Fully loaded I run around 46mph. My boat does not have bottom paint though.
 
I appreciate your inputs, and have organised to slip the boat for antifoul an will get the props removed to check pitch and diameter, but again i appreciate the assistance and prop spillage sounds like the issue, if i may ask what props do you have on your 270 as a matter of interest.

Are you drives moving to the full down position correctly? Check to make sure your trim cylinders on the outdrive are more or less fully compressed. What you are experiencing is something that would happen if the drives were up in any location (like cruise configuration). I'd forgotten to trim down once or twice and that will exhibit your symptoms.

Otherwise, like others have said this boat will move along nicely on plane. I often see 28-30kts @ 3600rpm cruise speed.
 
You could have a prop spinning issue where they are ok without too much load, say, at 8 knots, but as soon as you ask for more the rubber bush in the centre of the prop spins....and loads of exhaust gas in the water but no go............check and see if they have rubber centres around the splined piece...if they dont, it could be a nylon adapter....
 

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