320 stern drive trim question

R

rootbeerfloat

New Member
Oct 21, 2007
63
Chicago, IL
Boat Info
2005 320 Sundancer
Engines
MX6.2 w/Bravo III
Is there anyone else out there with a 320 w/ stern drives? (Boltman, you have a PM). I would like some feedback on how the boat responds to trim changes, how the trim indicators respond, etc.

I have smartcraft, so the trim indicators are numbers 0-10 on the smartcraft, not analog gauges. I find it extremely difficult to get the trim to set on the desired number, and next to impossible to sync the them. I really don't like the setup, but that's what it is. Anybody else have any feedback? Wondering if they are all like that or if I might have bad sending units, etc. Also, how high can you run your trim during cruise?

Thanks for any feedback.
 
I have stern drives on my 320 as well. I don't try to sync them by the gauge. I use the trailer switch to trim both drives up simultaneously. As long as you start with both in the full down position, that should keep them in sync.

I can only trim up a little bit before cavitation starts. I actually had "extenders" added to my stern drives to drop them 1" further into the water. Before I did that, I could not adjust the trim at all.
 
Mine is V-Drives, but I did test drive one with BIIIs. When I got her on plane and tried to adjust the drives trim it would cavitate. The dealer's crew and the captain told me not to use them. That made me think that using drive to improve performance was useless, unlike my 240DA. On the other hand, I also test driven Formula 31PC with the same power package and the drives trim did exactly what I had expected.
 
With the extenders I can tap the switch up twice for 1-2 seconds. I do pick up RPM and speed so believe I am improving efficiency. Before the extenders, I could not trim up at all.

My dealer added the extenders under warranty. Told me they see this infrequently. I guess the outdrives are not mounted in exactly the same position on every boat.
 
Thanks for the feedback.

DebtStar - I never thought about using the trailer switch. I just assumed the trailer switch would not work until at the high limit of stroke. Can you provide me more details - What actual setting are you able to run to before cavitation? Never heard of extending a stern drive...don't think I'll pursue that. I can definitely run mine at 1-2 on the smartcraft without cavitation.

Thanks again.
 
The trailer switch will work at any point to trim the drives up. I actually don't pay attention to the trim gauges as I know they are not accurate on my boat. I watched the dealer try to adjust them this spring and it was a very inprecise process. It's an analog "wheel" that is mounted to the side of each stern drive and they adjust it by loosening a screw and twisting the wheel. They kept trying to make the gauge read zero when the drives were both fully down but then as they raised them together, they started reading differently on each drive. Try as they might, they couldn't get them to read the same throughout their total range of motion. I'm not sure if this problem is unique to my boat, unique to the skill of my dealer tech, etc.

Once on plane, I hit my trailer switch 2x for 1-2 seconds each, watching my RPMs and speed and listening for cavitation in between. If I had to guess, I'm probably reading a 3 on my trim gauges at max trim. With time and practice, I have gotten the "feel" of the boat and how to dial everything in for the best performance.

Hope this is helpful. Let me know if your experience is different.
 
My trim gauges are a little erratic also. I go by amount of time that I push the switch. On my 280 the guages are 0-5(min to max trim) but on the previous boats it was 0-10(min to max trim).
 
DebtStar said:
I have stern drives on my 320 as well. I don't try to sync them by the gauge. I use the trailer switch to trim both drives up simultaneously. As long as you start with both in the full down position, that should keep them in sync.

I can only trim up a little bit before cavitation starts. I actually had "extenders" added to my stern drives to drop them 1" further into the water. Before I did that, I could not adjust the trim at all.
Click to expand...

Extenders?Never heard of these?Could you fill me in as to who makes them?Thanks
 
Yep. I understand that they come straight from Merc. There is a seam in the stern drive right above the props. This comes apart and they add a "spacer" piece, then reassemble. The extensions come in 1", 2" or 3" lengths. Adding these effecively lowers the props further below the waterline. Someone who understands hydrodynamics would have to explain to me what effect that has, but I can tell you that it helped me with my ability to trim the drives up, gain RPM and speed and not cavitate.
 
DebtStar said:
Yep. I understand that they come straight from Merc. There is a seam in the stern drive right above the props. This comes apart and they add a "spacer" piece, then reassemble. The extensions come in 1", 2" or 3" lengths. Adding these effecively lowers the props further below the waterline. Someone who understands hydrodynamics would have to explain to me what effect that has, but I can tell you that it helped me with my ability to trim the drives up, gain RPM and speed and not cavitate.
Click to expand...

In a way this makes sense to me. But I have a question, do you use the drives trim in combination with trim tabs or you don't use the tabs at all?
 
It depends on weather conditions. If fairly calm, I only use my trim tabs to "trim" the boat, which on my 320 usually requires pushing down the port side of the boat (I believe that is actually done by lowering the starboard tab, but I just push the down button on the port side on the helm - BTW - I like the way SeaRay labels the tabs, much better than my old Monterey!). If in heavy waves, I use the trim tabs to lower the bow into the waves for a smoother, but less efficient (and costlier) ride.

I don't want to hijack the thread, but this does make me wonder if other 320 owners have experienced the same tendency for the boat to be heavy on the starboard side, regardless of passenger load?
 
The way I understand that the drive has to be at the certain angle to provide an effect on performance. Thus, it appears that in 320’s application by the time the angle is reached it’s too much and cavitation begins. Therefore, lowering the drives with extensions would allow reaching that angle. I guess, that what is necessary to lift that heavy vessel little more out of the water.

There’s one more thing that I’m curious about, 320s are known for riding bow high (trim tabs up) doesn’t it bring the bow even higher when you’re trimming the drives? Theoretically, it should.

As for improper balance, I don’t feel that on my boat. In fact, I always use both tabs to either raise the bow when I’m on plane or lower the bow when coming off plane or need to provide more comfortable ride, as you had described, in the rough seas. However, if you experience this misbalance when you trim the boat and drives, the haul is at it’s highest point out of the water, which may have different effect on the balance. But, it sounds like you’re using only one trim tab right form the beginning, I assume before trimming the drive, so this tells me there’s a different problem to begin with.
 
My experience is similar to yours. . . I am running a 280SS, which is a substantially lighter boat.

2 x 2 second on engine trim seems optimal at cruise. Before this point, bringing drives up increases both GPS speed and RPM. Beyond that point. . .RPMS go up, speed goes down, speed is wierd = cavitation. Having analogue gauges without smartcraft, I don't have a precise impact on fuel economy due to trimming. In terms of trim indicators. . .they don't read anything at the point I must stop bringing them up.

Trying to bring the boat on plane with the drives in this "trimmed" position is a bad, bad thing- - the bow goes way up in the air, and the boat PLOOOOWWWSS its way onto plane.
 
Alex F - you are correct, trimming the stern drives up does raise the bow even higher. My boat definately runs bow high on plane until I reach 30 mph, then it drops level.

As regards leveling the boat, you are also correct, I am using one tab only on a consistent basis to drop the port side to level. As I think more about it, it may be because I do not have a generator (most boats up here don't). That might explain an uneven weight distribution from what SR intended and why I have to compensate.

Your thoughts?
 
DebtStar said:
Alex F - you are correct, trimming the stern drives up does raise the bow even higher. My boat definately runs bow high on plane until I reach 30 mph, then it drops level.

As regards leveling the boat, you are also correct, I am using one tab only on a consistent basis to drop the port side to level. As I think more about it, it may be because I do not have a generator (most boats up here don't). That might explain an uneven weight distribution from what SR intended and why I have to compensate.

Your thoughts?
Click to expand...

What happens if you don't use the drives trim, do you still have the leveling issue? At what speed does it start to occur?

Your assumption that it's due to the missing genset shouldn't be the cause of the issue, b/c most of them sit right in the center, well for v-drives anyway. I can't imagine this being the answer. It would make such a poor design for base model. Your boat should be still under full warranty, have you contacted your dealer?

Also, if you run at 30MPH+ on a regular basis, you have two negative things going on. 1-you're burning way too much fuel, 2-you're making your engines to work very hard. These boats are designed for cruising pleasure not for raising. We have several posts here and I've learned that it's best to keep these engines in lower RPM range (as close as possible to 3000RPM). It's not possible for me, b/c for mine the sweet spot is at 3600-3700RPMs. But,to run over 30MPH you must be pushing around 4300-4500RPMs and that's too much.
 
BOLTMAN, you're out there? Can you share your thoughts on the leveling issue? Do you have any?

Thx,
Alex.
 
Alex - I have the leveling problem even when I do not trim the drives. It appears as soon as I get on plane and is consistent at any speed unless I use the trim tab to compensate.

I never thought of this as a problem but you are making me wonder. I will ask my dealer.

BTW, 3700 rpm = 30 mph on my boat. I try not to run above 4000 for any great length of time.

Thanks!
 
DebtStar said:
Yep. I understand that they come straight from Merc. There is a seam in the stern drive right above the props. This comes apart and they add a "spacer" piece, then reassemble. The extensions come in 1", 2" or 3" lengths. Adding these effecively lowers the props further below the waterline. Someone who understands hydrodynamics would have to explain to me what effect that has, but I can tell you that it helped me with my ability to trim the drives up, gain RPM and speed and not cavitate.
Click to expand...

Any chance you could get me more info on these?Possibly a picture..Thanks in advance..
 
DebtStar said:
Alex - I have the leveling problem even when I do not trim the drives. It appears as soon as I get on plane and is consistent at any speed unless I use the trim tab to compensate.

I never thought of this as a problem but you are making me wonder. I will ask my dealer.

BTW, 3700 rpm = 30 mph on my boat. I try not to run above 4000 for any great length of time.

Thanks!
Click to expand...

DebtStar,
I had leveling issue on my 240DA and didn't consider this being a problem only because it took place when the boat had over 4-5 adults. I think it was not very well thought design. Fuel tank and water tank were in the center, all seating was on the port side leaving only the captain at the starboard side (helm).

According to boattest.com, most testing is done with 1/2 tank of fuel, 1/2 or so of water tank level and 2-3 adults.

If you have leveling issue by loading the boat as they do at boattest.com I would consider it as a big problem. Lets face it, even though, 30MPH @ 3700RPM is a good number (comparing to V-Drive, where I get 25-27MPH @3700rpm) your performance goes down to drain as soon as you apply that trim. Based on my experience, the idea is to get the boat out of the water as much as possible by raising the bow (both trims all the way up), this is where you achieve the best performance and efficiency. As soon as you bring one trim down to fix the leveling issue you're creating a drag, therefore loosing the performance. Thus, IMO, if you have to adjust as soon as you get on plane with only 2-4 adults on board it's an issue for boat like 320.

I did a quick search and looks like genset is installed on the port side with BIII package. However, I checked specs on kohler 5E (I have this one and I guess most 320s have them) and it weights 205lb (wet, without sound shield). I doubt that having those 205lb extra on the port side will fix the issue. I would make an easy proof of concept test by having your regular crew on board and then ask one of them (who’s weight is close to 200lb) move to port side. That person could hold on to the rail by the cockpit sink for safety. If you decide to do the test, I would do another one as well, which is to move all the crew to the port side, but make sure there’s enough room to hold on to and everyone is safe. I think it’ll take anywhere around 500-800lb (approx. 3-4 people) to resolve the leveling issue. I don’t think you’ll be thrilled to carry 800lb of lead weight for the test, so moving the crew for a minute would be the easiest way to do this.

If you do the test you would have really good argument for your dealer. If my theory is correct, they’ll have to do something and make sure that the issue is resolved. If anything, tell your dealer to get in touch with Sea Ray and get it resolved by the manufactory.

I would also use the following as part of my argument, a 320DA has official yacht certification, so if 2-4 people make the boat unleveled, then it becomes a piece of crap, not a yacht. But, I'd like to think of my boat as a yacht. If the dealer tells you a number of stories, then this theoretically means that the same number of people should drag anything smaller than 320 on one side all the time, right? But, it's not true.

Let me know how it works out.

Good luck,
Alex.
 
Thanks for the feedback, guys. It's been a very slow boating season for us around here, so I've really not had as much time as I would have like to play with the boat while running (especially in smooth wather). I hope to get out and spend the day on the water today, and NOAA is calling for waves less than 2' so I'm going to play with the trim using the trailer switch, run drives up until they definitely cavitate, etc. I'll let you know how it goes.

As for the listing, I've never noticed that on mine. Even though we haven't spent a tone of time on it, we've been out in all kinds of weather, loaded heavy and loaded light, and I've not noticed a trend. I have had to level it with tabs, but based on the conditions at the time I'd never question whether there was a problem. FWIW, I have a gennie on mine and it's installed in front of the engines just slightly off center to the port side. When you open the hatch and enter the ER, you'd step on the gennie.

Jeff
 
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