525 Question?
 

Are the 525's slow to make power. Have a single in 28', low power until 3000 rpm's and then will spin out the prop. Been told that's typical with a 525. Had engine on dyno looks like @ 2200 rpm is showing 200 hp, @ 3000 around 360 hp. You put 5 people on boat and take's almost 40 seconds to make power to plane out around the 3000 rpm mark, embarrassing

It sounds like you need to try some different props. What are you running for rpms WOT, what boat and what prop are you spinning. Need more info.

28 Bravo 4 blade, 28 Sunsation, and other boats like are running same prop.

For whatever it's worth. I have a 27 Donzi ZR with 496HO. Same prop (5,500 lbs dry weight). I also had trouble getting on plane. I think it's just the design of these smaller single engine boats, where weight is so far back, and power is inadequate. I asked people about going to 525, and most didn't think it would help take-off.

So, I put Mercury K-Planes on the boat. Now, I put them all the way down at take-off and it makes a big difference. Really gets up fast with just two of us on board. Had six on board this weekend, and it takes a little bit longer to get on plane, but still very reasonable.

Do you have K-Planes?

K-Planes help a lot for getting on plan, but if you are blowing the prop out, I'm not sure that will help. I'm not familar with the X-dim on the 28 Sunsation, but you may need to try a 5 blade. It seems like every boat is different. You might want to post over in the Sunsation forum and see if you can get any help.

bob,

Are you still having issues with the Sunny

40 seconds to plane out sounds like a problem to me. And not something that a prop change will fix if the boat runs correctly at WOT.

which 525 ?

Thats my thoughts too, but no codes, 100% available power, ran great on dyno.

Mercury Racing 525 EFI

My boat 30' w/525efi 26P Maximus seems to plane oK. I bring the RPMs up to around 3K, the prop spins a little but does not blow out.

I do notice that I don't really start picking up speed until I'm in the upper RPMs. The last 1K RPMs seems to give me a lot more speed.

How long does it take to bring up the rpms to 3K?

My 28p bravo is harder to get on plane than my 26p bravo. I think you will be happier with a 26p.

Not long at all and I usually try to take it easy getting on plane. I would say that I'm at 50% throttle or less.

How much throttle are you using to get to 3000rpm? Are you wide open? You should be able to punch the throttle and get as many rpm as you want while in gear from a stop, basically instantly, just by blowing the prop out(I wouldnt recommend this as it is a good way to blow a drive).

Unless you have super low slip with a super deep drive height, 40 seconds is way too long.

Give it some more throttle?????

I have a 454 procharged 288 and have the same promblem. I have started using the k planes more. I also run a bravo 30 prop now but i am looking for a 28 to see if it helps.

WOT comes up to 2200 and slowly pulls up to 2900-3000 rpm taking about 5 seconds and then takes off.

too much prop IMO, that boat with that power shouldn't even need WOT to plane out.

Maybe, but have rode in almost same boat/power/prop, but probably 800 ft lower altitude and ran good. Also if you just half throttle the boat to plane it feels no difference until you reach the majic 3000 rpm and you can feel and here the motor make power.

What is your WOT RPM?

I've been down this year to 4700, last year 5000.

Like already mentioned, too much prop. You should be propping for 5200.

So the same boat performs much better with the same prop, and you lost 300 rpms from last year? I know you scanned your engine for codes, but that doesn't mean it is ok. Codes do not always grab mechanical failures.

How many hours are on the engine?

Have you checked for leaking headers?

How old is the fuel? The 525 knock sensor will retard timing if you have fuel issues, which in turn will lower power. This can happen without a code.

Around 70 hrs., this is 2008 and knock sensors I was told are not used on the newer 525's. Had engine on dyno last spring and made good power, put back in boat just like it was last year. I check fuel pressure is good. Fuel is new, topping it off tomarrow. Headers where ok. Pulled plugs all look same, to me they looked a little lean.

You need to prop down and get into the peak HP. This will also help you with planing out. Try a 24 or 26 you might also gain some top end.

And I would try to find out why you are losing 300RPM. Nicks in the prop??