1999 3300 SCR not getting on plain

[Ron Owen dunfee]

I have a 1999 Maxum 3300 SCR with 454 7.4L Mercrusiers and Bravo 3 drives. I have owned it for ~4 years now and it's always been a struggle getting on plain. I have had it tuned up, new fuel filters, fresh antifoul paint on bottom and still doesn't get on plain very well. If it's just my wife and I on the boat it get's on plain, but a little slow. If I have maybe 6 adults forget it. Is anyone else having this problem? I would have thought with the big blocks it would have jumped out of the water (even given the heavier weight). Can other 3300 boat owners let me know if they have this issue (mostly those with a similar engine and drives). Thanks for any help anyone can provide.

[ertyqway]

With twin 7.4L engines, that boat should get out of the hole quickly. My 3200 SCR with twin 7.4s has plenty of get up and go.

However, every once in awhile, my boat bogs and can't get on plane. Every time this has happened, it's because the outdrives have somehow been trimmed wrong (often after my mechanic has been working on it). I solve this by trimming the outdrives all the way down, then trying to get up on plane, then retrimming them as necessary to even out the ride. Give that a shot and see if it works.

Otherwise, you may need to have your outdrives, props, and trim tabs checked out for damage and wear.

[Phillbo]

Try going to a 4 bladed prop. I had a buddy who's boat was a pig. He called the guys at Hill Marine and bought a set and it made all the difference in the world on the boats performance.

Hill Marine will guide you in the right direction. They are good people to work with.

[Ron Owen dunfee]

Thanks for your reply, I have 3 blade 48-823665 24P stainless steal props by Mercury Marine. Any idea if these are stock.

[biggerseagar]

These are dual props aren't they? Is the pitch correct? Do you put your trim tabs down ? That helps bigger boats get up on plane!

Roger

[ertyqway]

24 pitch should be pretty close to stock. I think mine are 23P. They may have changed the pitch with the model change from 3200 to 3300 (which is otherwise essentially the same boat).

I still think it's either your outdrive angle or tab trim creating the problem. Play around with the trim settings and see if you can get it out of the hole faster. Outdrives all the way down and trim tabs flat or slightly down ought to do it.

[biggerseagar]

Out drives should be all the way down. Trim tabs down also. Throttle should be agressively hammered down and off you go! Have you had a prop specialist look at your set up?

Roger

[ertyqway]

Originally Posted by biggerseagar

Out drives should be all the way down. Trim tabs down also. Throttle should be agressively hammered down and off you go! Have you had a prop specialist look at your set up?

Good point about the throttle. My boat needs to be at 3200 rpm to get on plane. I throttle up to that as quickly as I can without giving my passengers whiplash or kicking them overboard.

[mmwjr]

What is the WOT with just you and your wife and again with 6 passangers?

What size trim tabs do you have? Drop fins may help.

Twin big blocks should not be such a problem. How much gear is on board?

Are you certain the engines are healthy, compression test, ....

[RandR]

I have a 2004 3300 with 5.0 bravo 3 duo props. No issues getting on a plane. Outdrives almost all the way in and tabs half way down. Cruise at 3200 rpm on a plane at 19/20 knots

[shrew]

6 adults? Coolers? Weight needs to be moved forward.

[Ron Owen dunfee]

RandR,

What props are you running? When I do get on plain (with a lighter people load) it doesn't happen until ~25-27mph, but my top speed is ~40-45mph.

mmwjr,
Hopefully this weekend (weather permitting) I will do the RPM/Speed checks with just me and my wife on board. Then time permitting I will load it up with ~6 adults and repeat. Sorry, don't have this data yet and I know this is crucial to analyzing the problem.

Others, I have played with trim tabs and outdrive trim at various positions with no real help. The trim tabs do a great job keeping the boat level as needed, so I know they are functioning properly. Also, once on plain I have played with the outdrive trim and they also function properly (get a slight bump up in speed when at WOT and trim the outdrives up a little from full down. I have also played with rolling on the throttle verses WOT straight away and it seems the more throttle the better, but not the fix. Compression was good when I bought the boat, had tuned up and that helped a little early on, have fresh fuel filters, clean bottom, just normal gear loaded, clean flame arresters, and checked to ensure throttle cables were opening the throttle plates in carb fully (they were fully open). My son-in-law just bought a 32' 2005 Rinker with twin 350's and with more people and gear on board than I'm talking about jumps right up on plain, but tops out at 38-42mph.

[ertyqway]

When you say your boat is "not planing," what specifically is it that you are describing? Is the bow pointed way up in the air and the stern squatting into the water and bogging down? That would be typical of a boat that can't get out of the hole and is stuck on its own bow wave.

Your boat is "on plane" at any speed where it is moving across the surface of the water faster than its hull speed, which for a 3300 SCR is around 7 knots (8 mph). From 8 to around 15 mph, you are moving at semi-displacement speed. Beyond that, you are skipping over and outrunning your bow wave, which is pretty much the definition of "planing." So if you can get the boat up to 25 mph, it is "on plane," even if it doesn't feel like it. At 20mph with a 33 foot waterline if you were not planing your bow would be pointed essentially vertically into the sky and your engines would be straining gigantically to maintain that attitude. My boat may feel like it's going slow and bogging, but is still planing at 16 knots (a difficult speed for me to maintain unless I'm facing head currents).

If you can get to 40-45 mph at WOT, then I don't think you really have serious engine or outdrive problems. That's fairly respectable. I think I've had my boat doing 36 knots....ONCE.

You've got more horsepower than your son-in-law's Rinker in a similar-sized boat (roughly 12,000 lbs dry weight with a 32' waterline and 11' beam). You even have the same amount of deadrise as the transom (17-18 degrees). So it should be at least as fast.

Have you checked that the Bravo 3 outdrives are actually working as they are supposed to? Both props on each turning at full power and balanced?

[Ron Owen dunfee]

ertyqway,

Thanks for the reply. You raise a good point that when the boat is lightly loaded (i.e. my wife and I) and I can get on plain is ~10-15 seconds, but once on the boat moves really fast, so no serious engine or outdrive issues . With 6 full size adults the stern squats down and the bow is really high (tough to see over) - ~10-15mph and it just will not push through this and get on plain (i.e. 20-25mph).

What do you mean when you say, " are the outdrives actually working as they are suppose to"? How would you test if both props are turning at full power? I haven't had them balanced.

[ertyqway]

I'm not really sure what I mean. ;-)

Bravo 3s use two counter-rotating props. Are they both rotating at the same speed? Are they running without vibration and in balance? That kind of thing.

The additional detail you give on problem tells me it's probably a loading issue. When you've got a bunch of people in the cockpit, you're heavily stern-weighted. In that situation, you need to shift your trim tabs down a fair bit more to get on plane. This may be exaggerated if you also have additional weight items in the cockpit or engine compartment (e.g. a built-in generator). Move as much weight as you can to the nose of the boat (storage compartment under the forward berth when you know you're going to have a bunch of people on board.

.... or tell some of your guests to get out on the bow pulpit to get the nose down. ;-)

[RandR]

I don't know the exact numbers. But I can check next time I get to the Marina. They are stainless steel