Help propping a 300 suzuki
 

I've got a 2004 23 cc with an Armstrong bracket, 30" 300 Suzuki. I have ran the motor at nearly every height, with both an 18.5 suzuki prop and a 19 pitch lfs4. It seems to run best with the cavitation plate about 4" up from the keel. The boat tends to porpoise anywhere at mid-rpm range. It also will fall off plane anywhere under 3800. The best mpg I can get is right under 3, where I've seen most guys are easily getting mid 3's. Top speed is around 46 mph. My prop slip numbers are not great at all. Does anyone have any recommendations? Thanks

Try a 4 blade prop, I had to do it with my boat to enable the boat to plane at a lower rpm and a faster hole shot. My top speed dropped 2 mph but I picked up a better cruising speed, hole shot and similar mpg as with a 3 blade. My boat has a 20-degree deadrise and weighs about 6000 lbs so the best prop was a 15" diameter by 21.5 pitch. Oh, I also have a Suzuki DF300AP.

Mercury 22 pitch Bravo One 4 blade. Night and day difference from Suzuki props.

Did you see a significant increase in economy with the Bravo 1? My buddy just redid an older potter hull with a bracket and 300 Suzuki, and his boat is running great with the 18.5 Suzuki prop, which has me thinking that I may have some other issues going on.

To answer your question, no, in fact I lost a slight amount but gained significant improvements in sea handling, ride and stable stern lift.

No matter how simple it seems, the fact is there is not one 23 SeaCraft that will match performance with any other if modifications have been made outside of factory offerings. Heavily modified refits are even more of a mystery but can be tamed with diligence and the availability to finance the needed changes.

First off, you need to collect the base data and document it. To do it right you need have the boat configured to how it will be loaded and used: fuel level, gear, ice and people. Next, have the instruments needed to provide speed, max rpm, fuel burn and trim percentage. Digital readings are best and can usually be attained on a single screen on most modern chart plotters. Test runs also should be in the same sea conditions. If tide current is a factor you can record runs in both directions and average the results.

Many people don’t have the patience and persistence to perform these prerequisites and rely on setups reported from other builds and configurations. Don’t fall into that trap! Go get us the above stats, cavitation plate distance from the keel level and we will be able to give you way better input and recommendations. We also will argue and side track with each other like a bunch of cranky old men. :D

Thanks for the reply. My motor is currently about 3 1/4" above the keel, I was trying that, as that is what Armstrong recommended. However it definitely runs the best 1 hole up, putting me at 4". I have a pretty detailed spreadsheet of my different props and performance numbers- but they aren't very consistent with load, tide, etc. I took my 18.5 prop in to have it worked, and it turned out a couple blades were bent, and he is going to add a little cup to try and keep me hooked up better. I also removed a large total scan transducer from the transom that was fairly close to the center line. I am hoping that raising the motor back up, repairing the prop, and removing the transducer will get me where I need to be, but we will see. I've got the funds and patience to get it right... but of course I'd like to figure it out sooner than later.

Can we see pics of the transom/bracket in a few different views? I am also confused on the Suzuki prop size. My Tsunami is no lightweight but will spin a Zuke 3 blade 20’ pitch to 6000 loaded.

Here you go. I can barely see 5900 with the 18.5 and a light load. The boat sits good in the water, so I don't think its a weight issue. No water in the bracket.

Well, that is your problem right there.
Your boat is upside down!

My observations on the 4blade prop are inline with Kmouse’s. Lost a couple mph but gained in lift and sea keeping. I also was able to raise the engine up all the way . In your picture is the motor tucked down completely or can it go more? As it looks trimmed up( might need wedges ?) Have you tried lifting the motor higher ?

There are a couple of things I would look into before I would pursue any more prop mods. First off, even the best bottom paint job is going to cost at least 1-2 knots. If it’s in need of bottom paint and is really rough and thick I would consider a strip and paint. One other thing is how high the water stain line is on the hull. I would go fill her with fuel and get a good weight on the hull at the nearest truck stop. Several of us have 300 Zukes on our 23’s that float at rest with the rear, outside chine at the waterline with no people aboard. Rule out the heavy hull first before we start talking about bracket height, setback, tabs and overall hull COG.

You have a great boat and like the rest of us owners, we all want the best performance. The knowledge base of members here will help you get there.

Bottom pain will cost you about 8-10% in top speed. A boat that runs 45 with a clean gel-coat hull will drop down to about 41 with most ablative bottom paints. Painted hulls also ride lower at the bow at a given trim angle because of paint-induced drag.

Moose is right: weigh your boat. Your Armstrong bracket is NOT a full flotation bracket, i.e.; it does not support the full weight of your motor. It mitigates the weight somewhat, at best.

With that bracket, you REALLY should be using a 4-blade prop to provide stern lift and maneuverability. And whether using a 3-blade or a 4-blade, remember to "prop for Max of Max at Max"

That means to prop so that you can achieve the MAXimum end of your MAXimum recommended RPM range when the boat is at MAXimum loading.

You may sacrifice some top speed, and be able to go above the maximum rpm range when lightly loaded, but you put a whole heck of a lot less strain on your motor that way. (And just because you can exceed the maximum recommended rpm, don't. Your motor will thank you for that, too.)

Have you gotten anywhere trying to figure out your issue? Just curious!

I had my 18.5 Suzuki prop reworked, which turned out to have 2 bent blades, and it was very out of balance. That did improve performance, but I still need to raise the motor back up one hole. I still want to weigh my boat too. It’s interesting looking at pictures of the 23’s in the water, as the weight balance seems to vary greatly. My buddy with the potter hull’s bow sits about 5” higher than mine at rest. You can see the third chine out of the water on his. His stern also is a couple inches lower than mine. But it does look like a lot of the newer models like mine sit lower at the bow with lighter motors like the optimaxes. I’ll report back when I raise the motor.
Sorry I don’t know why the pictures are sideways.