prop for 2320

I have a 2320 with 225yahm 4s I raised the motor as high as it will go. I am at 54=5500rpm wot motor trim 1/2 up tabs 1/2 down, I have the black 17t prop just had it redone. I am thinking 15deg prop but no sure which one 2deg should get me to 58=5900rpm Top speed is 35-36mph any suggestions?
thanks Walt

Just curious why you are running that level of speed with that combination of engine trim and more importantly, 1/2 tabs? More curious about the tab setting?
Anyway, I have the same motor (don't know your year) on a 2120 and my top speed is 43 to 44 at 5900 to 6000. I think we have the same prop which is the Yamaha Black Steel 15x17. My boat is maybe around 1K lighter? That is part of the speed difference. Also, are you running in fresh water? If so, that may account for some speed loss also. I'll see what others say about that?

Check this site out and play with different options to see prop choices. 17P is about where you should be. You could reduce diameter to 14.5 or you could stay at 15 and reduce pitch to 16 or so. Both concepts will increase RPM.
https://www.mercurymarine.com/en/us/pro ... #/step-one

Those trim tab setting are concerning. Have you considered adding a Permatrim? I was wondering if your tabs were the attempt to correct porposing?

Shawnee I have a 2011 and I run in fresh water. I run 1/2 tab because that gives me the best ride, I played with trim and tab more/less tab I lose rpm. I also tried more trim and I start to porpise.

If your boat is a 2011 then I'm not sure if you have the new 4.2L F225 or not? Anyway, these 2120's and 2320's run kinda ass heavy. Assuming that your engine is functioning at 100% I would put a Permatrim on it. I know most people hate to do this type of add on to their boat, but it works. You have raised the motor which was probably needed, now finish it off with a Permatrim. It will lift the stern, eliminate the porposing and eliminate the need to run WOT with any tabs except what little you need for leveling the boat. If you are running at cruise speeds and not WOT, and you are using more tabs to drop the nose down into a head sea chop for ride, that is one thing, but as a normal thing, no way. At WOT you should only be using engine trim, as much as possible which is just shy of your prop cavitating, and tabs just to level. If you put this Permatrim on, that is how you will be able to run. After that, if you still need to tweek the prop then I would go that route. I personally don't think a lifting prop will accomplish all of it on its own. A combination would be my thoughts. There are many here on this site who have documented this. Continue to do some more homework and maybe others here will confirm this also. Good luck.

What will a Permatrim do for my low WOT rpms, I know it will lift stern. I have the 225 4.2 4stroke Yamaha says 6000rpm at wot, I need to increase rpm.

WAJSKI":2105cre0 said:

..........raised the motor as high as it will go. I am at 54=5500rpm wot motor trim 1/2 up tabs 1/2 down, I have the black 17t prop just had it redone.

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Before my 2006 2320/f250 I owned the 2004 Parker 23 center console DV/bracket/f225 which is very similar to your setup. In 2004 the 23DVCC came with the same prop you have which is the 15x17t black prop. Not exactly a high performing prop. The hull ran much better with either a yami SWS 15 1/4x17 or the Merc Mirage 15 1/4x17. Assuming a healthy f225 you should be right at or very close to 6k rpm.

To properly test for max rpm it is important to run the boat with a light to moderate load.......1/2 tank of fuel, 2 guys no gear is reasonable. At full throttle tabs must be up all the way. While traveling in a straight line gradually bump up the engine trim. The rpms will continue to increase as well as speed until the prop hints that it wants to blow out which is indicated by an increase in rpms but not corresponding speed. At this point you can bump down the engine trim a hair and read the rpm. This is your max rpm with the tested prop. The purpose of this test is to decrease hull wetted surface area/friction with the water to allow the engine to achieve max rpm. The prop is nothing more than a final output gear in the scheme of things. Hitting close to 6k rpms just lets you know you have the right "gear" attached to the prop shaft. After testing and choosing the right prop it's no longer important to hit 6k unless you're testing a different prop or have modified the cup, pitch or some other aspect of the current prop.

WAJSKI":2105cre0 said:

What will a Permatrim do for my low WOT rpms, I know it will lift stern. I have the 225 4.2 4stroke Yamaha says 6000rpm at wot, I need to increase rpm.

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The permatrim lifts the rear of boat changing the running attitude of the hull making it more efficient in the water. Whereas you were using some tab in your WOT prop test which is a huge drag on rpms, you will not need any tab to effect efficient running attitude at all. To answer your question directly, the permatrim by itself is negligible in helping low rpms other than the gain you will get from NOT using tabs which rob rpms. And while the permatrim in theory adds drag to the lower unit, the efficiency afforded to a more level running hull negates the drag factor. IMO the hull is also more responsive from a handling standpoint with the permatrim. And believe it or not adding that additional hull planning surface that far aft changes the pitch axis of the hull slightly which makes the hull ride longer (more like a 24/25 rather than a 23) which certainly has its advantages in certain seastates.

Getting a boat perfect is always a challenge. Good luck.

Thanks Shawnee and Jim, I am going to order permatrim then prop

Thanks for answering that Grouper Jim. I have nothing to add as he has covered it. By the way, Grouper Jims post and results on this topic, along with his help on mine are why I did the mod. You will be happy with it. Let us know how it works out.

I agree with the permatrim. I have one too. Get it from Andy at sim Yamaha.

X4 on the permatrim its the best upgrade I've done to my parker.



My RPMs actually went up
I gained a couple of mph
I can keep the boat on plane @ 16mph in rough seas
Gets up on plane alot sooner
Boat rides alot better in rough seas
I don't have to use the trim tabs to adjust the bow


All that for less than $200 bucks delivered to your doorstep.

WAJSKI":3ddx1bdn said:

I have a 2320 with 225yahm 4s I raised the motor as high as it will go.

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I forgot to comment on this. My recommendation is to start low. With Parker that usually means the engine came from the factory all the way down in the bottom hole. Do your mods, test for desired function, then raise the engine one hole, retest. Keep raising the engine one hole at a time until you experience a negative in handling or the prop starts to ventilate in a following sea. The permatrim will actually allow you to run one hole higher than without.

To save you some research. My 2006 2320 f250 w/18" tabs preferred the bottom hole which is where it was from Parker. I carried most of my weight in the boat forward do to the PH design. Raising the engine one hole on the 2320 would result in some prop ventilation in certain following seas. For me and how I ran my boat my best handling was down in the bottom hole.

With the 2004 23DV f225 the highest position for optimum handling was one hole up from the bottom.

Wajski since you are already all the way up, start there and if needed work your way down. I am going to venture a guess that one up from the bottom will put that permatrim where it needs to be for best lift/handling benefits. It's important to remember that the antiventilation plate on the lower unit is also a control surface. It's the only control surface on the boat that allows you to lift the bow (via motor trim). Keep in mind that taking the A/V plate out of play or reducing its effectiveness by moving the motor too high does change handling characteristics. One issue would be porpoising which you have mentioned.

As a disclaimer I also wanted to add that the above recommendations apply only to the Parker 23DV hull (with a bracket). I have had people on this and other forums tell me that 25 dv bracketed hulls responded in a similar fashion to the permatrim but I don't have the first hand experience with the 25 hull, just anecdotal. And I also realize that high performance boats trying minimize drag and maximize top end want to run the A/V right at the surface of the water but in my experiences that is not where the 2320 with a bracket handles best.

As always.....YMMV

It's important to remember that the antiventilation plate on the lower unit is also a control surface. It's the only control surface on the boat that allows you to lift the bow. Keep in mind that taking the A/V plate out of play or reducing its effectiveness by moving the motor too high does change handling characteristics. One issue would be porpoising which you have mentioned.[/quote]

Jim, since adding the 12x18's a few weeks ago and now having some running time with them, I'm noticing a little porpoising at high RMP speed has returned. I was running with 3/4 plus fuel load. When I did the Permatrim, I raised the motor all the way up and it was doing great. I suspect that with the bigger tabs and added lift, its got my AV too high? Do you think dropping the motor back down will correct this?

shawnee83":3ud88116 said:

Jim, since adding the 12x18's a few weeks ago and now having some running time with them, I'm noticing a little porpoising at high RMP speed has returned. I was running with 3/4 plus fuel load. When I did the Permatrim, I raised the motor all the way up and it was doing great. I suspect that with the bigger tabs and added lift, its got my AV too high? Do you think dropping the motor back down will correct this?

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That's why I start low then raise a hole..........it makes it easier to tweak performance. It's quite possible especially if a touch of tab from those 18s doesn't resolve the issue.

shawnee83":3l5k7l8h said:

It's important to remember that the antiventilation plate on the lower unit is also a control surface. It's the only control surface on the boat that allows you to lift the bow. Keep in mind that taking the A/V plate out of play or reducing its effectiveness by moving the motor too high does change handling characteristics. One issue would be porpoising which you have mentioned.

Click to expand...

Jim, since adding the 12x18's a few weeks ago and now having some running time with them, I'm noticing a little porpoising at high RMP speed has returned. I was running with 3/4 plus fuel load. When I did the Permatrim, I raised the motor all the way up and it was doing great. I suspect that with the bigger tabs and added lift, its got my AV too high? Do you think dropping the motor back down will correct this?[/quote]
Good answer. Everyone is raising there motor on parker boats. Yes, you go faster and get better gas mpg. You give up something to get something. Raising the motor makes the ass end drag. I raised my motor 3 times. Now I'm back to all the way down. What I did is buy biger tabs. 12x24. I am so happy the way my 2320 rides. The lift is great!! When you raise the motor the bow goes up and the ass goes down. Now you have to use the trim tabs, that is ok. That's what tabs do but!!!! What happens is you start to get a pounding in the bow and that makes for a hard ride. Maybe it's all about speed? For me, I got a parker to have a nice ride. That's my 2 cents.

Not about speed for me Marty. I just want the boat to ride and perform at its best. I would choose ride over a little speed any day. The order in which I did my mods was not optimal in hindsight. If I were to advise at this point, I would recommend doing the tabs first then maybe the Permatrim then maybe a prop then maybe raise the motor?? That said, on mine, the Permatrim has still made the biggest difference overall on my 2120. I think I may end up dropping my motor back down 1 more hole (maybe more??)eventually though?? I only experienced a little proposing return 1 time while doing a brief WOT session in a strong head current returning to the docks. Last month I ran out to the stream (about 27 to 30 miles) in some decent swell of 3's & 4's and provided plenty of opportunity for blow out or cav issues and all was fine both into the swell and returning on the stern. My F225 is very heavy for the 2120 so I do think it's possible all the way up is correct, or very close to correct?? I'm going to run it the rest of the season this way and continue to evaluate it though. Yours and Jim's comments definitely noted on the mounting height. If I change it I'll have my mechanic do it in the fall when I have him put a new water pump on etc during PM's. I'll update any changes on this hot topic.