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Author Topic:   Propeller upgrade or Trim Tabs
Georgetech posted 12-22-2004 09:31 AM ET (US)   Profile for Georgetech   Send Email to Georgetech  
Hi Everyone
I am debating which of these two items will be more beneficial to improve the ride quality in the confused rough choppy waters of Raritan Bay and Sandy Hook channel. I'm running the standard aluminum propeller 12 3/4 x 21 on my Mercury two cycle saltwater classic with good results but could be improve.
a)Upgrade to a stainless steel "High Five" in 12 3/4 x 20.
b)Install Lenco Trim Tabs.
Any opinions?
highspeed_jd posted 12-22-2004 10:40 AM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
What kind of boat do you have? Trim tabs would give you a smooter ride. With the tabs you can adjust them to raise the bow and hande rough water better. The prop wouldn't make any difference at all.
kingfish posted 12-22-2004 10:51 AM ET (US)     Profile for kingfish  Send Email to kingfish     
As per highspeed_jd, we need to know what boat and motor you have to help out.

I must respectfully disagree with Highspeed_jd about what trim tabs will do for a boat though - they will allow you to raise the stern, thus lowering the bow. They will not raise the bow. Most cupped propellors will allow you to trim your motor up (out) further without blowout, which in turn will usually result in more bow lift. The idea of a smoother ride from trim tabs is to lower the bow into the chop to "cut" the waves.

highspeed_jd posted 12-22-2004 11:11 AM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
But if you put the bow down, then the boat will cut into the waves and make your boat get crazy. I am talking about 2 or 3' chop out in the Gulf. Kingfish is correct if your in about a 1' chop in a 18 or 19' boat. It just amtters what kind of boat you have and the conditions that you are using it in. I usually run offshore in sometimes 5' swells.
highspeed_jd posted 12-22-2004 11:13 AM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
I can't type today. It must be the blue norther blowin' in!!! Calling for snow Friday!!! It hasn't snowed down here since '89.
Georgetech posted 12-22-2004 11:56 AM ET (US)     Profile for Georgetech  Send Email to Georgetech     
Hi, Guys
I apologize, the boat is a 2003 170 Montauk.
highspeed_jd posted 12-22-2004 12:02 PM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
Then you should probably follow Kingfish's advice. He is one of the more knowledgable of the members that post here.
kingfish posted 12-22-2004 03:21 PM ET (US)     Profile for kingfish  Send Email to kingfish     

Flattery will get you everywhere and I appreciate it; however there are some folks here who might take issue with whether I am one of the more knowledgable types around here or not ;-)...

Having said that, I still stand by my statement that trim tabs can't raise the bow of a boat; doesn't matter what size. My personal experience is with an Outrage 22 and a Parker 2520. Doesn't matter whether you're in 1' chop or 5' chop, if you lower your tabs so they come in contact with the water flowing under the stern, they will act to raise your stern to the degree they are lowered. When the stern goes up, the bow goes down.


There are a lot of folks who will tell you that tabs are overkill on a Montauk, and even on an Outrage 18; I don't necessarily disagree with them. I would strongly recommend you start out by investing less than $50.00 on a hydrofoil like a DoelFin that installs on the anti-ventilation plate of your motor. If your motor is installed on your transom for maximum performance, the A.V. plate will be above the water at high planing speeds, and so therefore will the hydrofoil. At sub- and moderate planing speeds, the hydrofoil will act like tabs in that it will help lift the stern and lower the bow, providing a smoother ride in chop and allowing you to maintain plane at lower speeds.


SteviLad posted 12-22-2004 03:35 PM ET (US)     Profile for SteviLad  Send Email to SteviLad     
Do you think that a hydrofoil, like the doel-fin, would be worthwhile on a 19 ft Nantucket with a 150 Optimax, before going to the expense & effort of installing trim tabs?
highspeed_jd posted 12-22-2004 03:36 PM ET (US)     Profile for highspeed_jd  Send Email to highspeed_jd     
You are right. I didn't mean that it actually raises your bow but it does let it come up if you pull the tabs all the way up.
kingfish posted 12-22-2004 03:50 PM ET (US)     Profile for kingfish  Send Email to kingfish     

Yes I do, *if* your motor is installed such that your A.V. plate is above the flow of water below your stern at planing speeds. For my money, if a motor is not installed in that fashion, it should be raised until it is, anyway.


boxers posted 12-23-2004 04:29 PM ET (US)     Profile for boxers  Send Email to boxers     
I tend to agree with the idea of trying a doelfin first, just as Kingfish suggests. We have experimented with three boats 13ft 18ft and 20ft. On the lighter hulls the doelfin works wonders BUT once the hull gets to be much over 1500-2000lbs the ability to lift the stern is minimal so and all your gaining is parasite drag. A Montauk being fairly light would likely benefit from the doelfin modification. If the issue is port/starbord listing then tabs are the only way to go.

Our 13ft is amazing you can adjust the bow height very precisely (with the doelfin) for the perfect ride with 1-6 people on the boat. Not all boats require stern lift but these heavier four strokes tend to overload the transom. As does our 200lb Honda BF40 on a 13ft GLS hull.

Merry Christmas,


Georgetech posted 12-24-2004 03:29 PM ET (US)     Profile for Georgetech  Send Email to Georgetech     
Thanks everyone for the input, but I do not want to drill holes in my new engine. I think the high five stainless steel propeller due to thrust increase will help the 170 to stay on plane at lower rpm's resulting on smoother ride. The trim tabs achieve the same result but adding friction and friction = gas at the pump.
fishinchips posted 12-24-2004 08:16 PM ET (US)     Profile for fishinchips  Send Email to fishinchips     
hydrofoils do work.
The benefits are:
1. Get on plane faster
2. Able to plane at a lower rpm
3. Smoother riding, your bow cuts the water better because you are planning.

I have installed a Cobra Edge Pro on a 2003 - 170 montauk with a 90 hp 4 stroke.

1. Need to drill holes in to the cavatation plate.
*but the fin is mounted under the cavatation instead of above it and also its one peice design.

newport jack posted 12-25-2004 07:33 AM ET (US)     Profile for newport jack    
Going with the prop is not a bad idea, try it see how she runs. I have had doel fins on two boats and am putting a pair on my 20' Revenge, I like them a lot,the boats "pop" up on plane really quick. I would much rather drill four holes in my motor then drilling all the holes in the transom of the Montauk. Going with the stainless prop sounds like a good idea, always can remove it and no holes!.................Jack
davej14 posted 12-25-2004 10:14 PM ET (US)     Profile for davej14  Send Email to davej14     
If you don't want to drill your cavitation plate, the "turbolift" fin clamps to it without drilling. It is more costly, but it is stainless steel and quite durable.

Dave J.

SteviLad posted 12-26-2004 11:59 PM ET (US)     Profile for SteviLad  Send Email to SteviLad     
Have not been able to find "Turbolift Fin".
Tried several searches...any idea who carries them?
Are they as effective as the Doel Fin?
Georgetech posted 12-27-2004 07:03 PM ET (US)     Profile for Georgetech  Send Email to Georgetech     
check the the people at Thehulltruth forum semm to like them very much. I like the propeller guard design at
WT posted 12-27-2004 08:41 PM ET (US)     Profile for WT  Send Email to WT     

Call Boston Whaler customer service. I was told by a person that answered the phone that if he were to buy a hydrofoil, he would get the Turbolift from Grand Isle Marine.

Here's a link:

If I get one, I will also get the Turbolift.


mikeyairtime posted 12-28-2004 12:49 PM ET (US)     Profile for mikeyairtime    
I'd opt for an aluminum or composit tab in the marine environment. I don't think I'd want a big piece of steel, stainless or not, bolted to my aluminum outboard.
kingfish posted 12-28-2004 03:06 PM ET (US)     Profile for kingfish  Send Email to kingfish     

It's your boat, and certainly formulate your decisions regarding what you want to do with it in ways that please nobody but you.

I will offer though that the holes that are required for a DoelFin in your AV plate are a real non-issue and are easily repaired if you find you don't like what the hydrofoil does for you, or if you decide later on you want to graduate to tabs. I really don't think changing out props is going to get you to where you want to be; but, especially if you can get a loaner to try out, give it a go and find out for yourself.

Georgetech posted 12-28-2004 07:25 PM ET (US)     Profile for Georgetech  Send Email to Georgetech     
Thank you Kingfish for the advise.
I want you to know that in the past week I have read every single post here and in other forums regarding propellers,trim tabs,hydrofoils and propeller guards that act as hydrofoils. My conclusion is simple:
a) No engine manufacturer installs hydrofoils or designs their AV plates wider to accomplish stern lift.
b) The boat manufacturers includes recommend and install trim tabs no hydrofoils.
c) Trim Tabs give you sternlift plus side to side adjustment which results in better handling of the vessel throught rapid changing sea conditions.(no hydrofoil will do that).
d) Going from aluminum to stainless is an upgrade in material for durability and performance nothing else.
e) Will consider a propeller guard to protect animals,people and my investment.
Sorry for the long post.
kamie posted 12-28-2004 08:13 PM ET (US)     Profile for kamie  Send Email to kamie     

I would disagree with d. Try going to a SS prop first. You will notice a big change in how she handles and responds. You will probably still go with the tabs but going from Alum to SS prop on my 18 made a huge difference in how the boat handled.

kingfish posted 12-29-2004 09:39 AM ET (US)     Profile for kingfish  Send Email to kingfish     

Regarding a:
Outboard manufacturers *can't know* what boat their motor will be installed on nor can they know what the specific conditions the boat/motor combo will be used in nor the specific performance desires of the eventual owner, so they'd be foolish to limit the performance possibilities of their motor by widening the AV plate or adding hydrofoils at the factory.

Regarding b:
Some boat manufacturers sometimes add trim tabs at the factory; sometimes the decision is made by the boat manufacturer and sometimes the decision is an elective one made by the dealer or the buyer. Adding aftermarket accessories *to the motor* (like hydrofoils) at the boat factory would be foolish for the same reasons stated above. This by definition would fall into the purview of the dealer or the buyer.

Regarding c:
No argument; but a propellor change won't do those things either.

Regarding d:
DoelFins are plastic.

Regarding e:
Whatevere floats your boat.

I am a solid proponent of trim tabs, and a specific fan of Lenco electric tabs; I have them on an Outrage 22 and on a Parker SCMV 2520, and consider them a critical component to the performance of both boats. I am not arguing against tabs, just stating a possible progression of performance adjustments at very low cost to a boat the size of which very few people choose to put tabs on. Tabs may be the perfect thing for you.

kingfish posted 12-29-2004 09:42 AM ET (US)     Profile for kingfish  Send Email to kingfish     

Comparing propellor change outs to the addition of trim tabs is comparing apples to oranges - two different things done for two different sets of reasons.

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