Squirt with 25HP, Lots of bouncing, Trim Tabs?

Report the performance of your boat, supply as much information as possible (weight, HP, prop, speed, etc.).
Subject: Make the Glen-L design name the subject. If the design already has a posting, add your information to that post.

Moderator: Bill Edmundson

User avatar
BayouBengal
Posts: 1013
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BayouBengal » Sun May 30, 2010 9:51 am

Having a desire to get to a little faster cruising speed, I've given up on matching a vintage motor to my 11 foot Squirt for the time being. I bought a 1991 Evinrude 25 HP with SS Prop 10" x 15 Pitch, slightly cupped (standard prop for this motor is 10" x 13 Pitch). Brought the boat out yesterday with the new motor. We went out first thing in the morning and their was only a very mild chop on the lake. The boat went 25 mph with two adults, approximate combined weight of 375 pounds. I don't know the speed with me alone, but it was considerably faster. I also think the boat would have went much faster if I could have ever gotten it trimmed out.

The boat is a totally different ride now. Previously, I had a vintage 1956 Johnson 15HP on the boat and my complaint was a top speed of only 19mph with two adults, but the boat rode very smoothly and handled chop extremely well. Now the boat seems to bounce all over the water even at slower planing speeds, and it's especially bouncey when only one person is in it. Also, the motor only has manual trim and is trimmed all the way down. Trimmed any less than all the way down, the bouncing problem is much worse.

By the way, the difference in motor weight is 117 pounds for the newer 25hp, the vintage Johnson weight was 85 pounds. Additionally, my 6 gallon fuel tank is mounted in front and was about half full during the run yesterday. Previously while running the vintage 15 hp I had my battery mounted up front to help get on plane, but I moved it to a location just behind the seat when I changed out to the 25HP. Also, because the 25hp has a charging circuit on it, I went with a much smaller battery. My previous full size battery weighted in at 47 pounds, the new battery weights only 22 pounds, so this somewhat offsets the additional weight of the motor. The boat seems to sit very well in the water and doesn't draft much at all.

Best I can tell, the transom is flat and trailing edge is crisp, I don't think I have a rocker. I've heard that props can actually cause porpoising, although I don't understand how this can happen. I initially wanted to avoid trim tabs because of the aesthetics, but I've already thrown in the towel on the aesthetically more attractive vintage motor, so, if you all think trim tabs will do the trick, please suggest which kind I should get.

Any input and suggestions regarding the bounce would be appreciated.

User avatar
galamb
Posts: 811
Joined: Sat Jan 17, 2009 1:37 am
Location: Inverary, Ontario - Cuddy Sport (modified)
Contact:

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby galamb » Mon May 31, 2010 9:29 am

You could try a fin on the cavitation plate (doel-fin is a brand name you could check out).

A fin (or hydrofoil) does make it tougher to steer and puts some significant stress on the cav plate (bad enough that it actually broke the case on some Suzuki models), but it does really help keep the nose down.

If you want to go with tabs you can check out "smart-tabs" - they are relatively inexpensive (as far as trim tabs go) and are self adjusting...
Graham

Yes, Plywood is "real" wood :)

A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

User avatar
ttownshaw
Posts: 2337
Joined: Thu Mar 01, 2007 7:33 am
Location: Owasso, Oklahoma
Contact:

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby ttownshaw » Mon May 31, 2010 11:53 am

A lot of builders have determined that more trim "in" will help. Several have added wedges to their motors to get this additional trim. This is what I'd suspect since trimming out only worsens the problem. Might be worth a try before going the trim tab route.
Bill

I told my wife we needed a three-car garage for my projects...she told me to ask her for permission next time before I buy a house.
http://www.unitybuild.net

User avatar
galamb
Posts: 811
Joined: Sat Jan 17, 2009 1:37 am
Location: Inverary, Ontario - Cuddy Sport (modified)
Contact:

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby galamb » Mon May 31, 2010 4:54 pm

Yes, Bill's comments got me thinking again (that's dangerous sometimes).

When rigging higher horsepower boats - bass boats in particular, that really have too many horses for the size of the boat, we mount them a couple inches higher than "normal".

In most outboard rigging it is recommended that the cavitation plate be mounted "in line" with the lower edge of the transom.

However, on (fast) hulls, for lack of a better term, we will mount so that the cav plate is 2" to 3" higher than the bottom of the transom (we raise the whole motor which is thru-bolted to the transom, or better yet, mounted on an adjustable jack plate so further "tweaking" can be done).

Merc publishes charts for mounting heights of motors in excess of 150 horses which takes some of the guess work away from that application - but no reason to believe it would not have the same effect on a smaller motor in specific situations.

You must be careful that you don't mount so high that the prop, or worse, the water intakes, break the surface, but the effect of the higher mount is less steering torque, more top end speed (due to reduced drag) and less porpoising (not sure I spelled that one correct).

So, something you may want to fiddle with.

Jury rig something up to raise the motor say 1" to start and give it try....
Graham

Yes, Plywood is "real" wood :)

A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

Scott
Posts: 308
Joined: Sun Sep 17, 2006 3:21 pm
Location: Canada, Southern Ontario
Contact:

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby Scott » Fri Jun 04, 2010 5:35 am

Your going to have lots of headaches and spend a lot more money than you intend to. I went through the same with my 4 stroke. Shims, trimming, weight positioning, tabs, props, hydrofoils...etc.

With more weight in the front your going to create momentum if the porpoising keeps up which it'll make it worse. Like others said on here trim tabs will just create drag and a sad face. They do help but they are more for planning.

Hydrofoils did help a bit, but it reduce speed too. Plus it'll increase drag more than you think. Think of the degree angle the motor will be in when you trim up, then add the surface area of the hydrofoil and drag you will be making with it.

I'm not trying to discourage you, just giving you a heads up.
Thun.der.bolt
ˈTHəndərˌbōlt

A flash of lightning with a simultaneous crash of thunder.

An ignition system of early Mercury outboards that not only is a nightmare to diagnose but also improves a marine mechanics competency.

User avatar
BayouBengal
Posts: 1013
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BayouBengal » Sun Jun 13, 2010 4:15 pm

Your going to have lots of headaches and spend a lot more money than you intend to. I went through the same with my 4 stroke. Shims, trimming, weight positioning, tabs, props, hydrofoils...etc.

Looks like you're probably right. I put the smart tabs on and it slowed me down considerably, 20 mph with two adults, 23 with me only. I loosened the tabs as much as possible, but it doesn't seem to matter. I'm going to try to go to the propeller which is standard for the motor (a 10 x 13). Right now I'm running a 10x15 on advice that the boat is too light and might over rev with the 10x13, but with the smart tabs the motor seems to really labor and I can't believe how much gas it's burning. If the smaller pitch prop doesn't do it, I'm going to call Nauticus and see if they'll exchange my tabs for the next size down.

If neither of these ideas work, I could go to a 30 hp which is actually the same weight as my 25, but I probably won't. I'll probably just settle for a little slower boat than I'd like to have.

BTW, while the drag on speed with the smart tabs is disheartening, I must say I really like the feel of the boat with them; it planes all of the time regardless of how slow you're going.

Oyster
Posts: 4408
Joined: Sun Jul 02, 2006 7:10 pm
Location: North Carolina

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby Oyster » Sun Jun 13, 2010 5:24 pm

Foils mounted to the motors yells ugly IMO. Depending on your bracket width at the yoke, there are wedges made out of alum to increase your trim angle, bolted in place between your motor and transom. Its also really easy to add a plywood wedge to the transom which is done on many boats with a bit more work in the experiemental stage. If you look to the left side of the photo, you will find a piece of 3/4' plywood planed down to nothing at the bottom.

These are the transom wedges. For 30 bucks or so..
Most outboard motor shops or good outboard motor dealers sell them. Worth a try. We have been adding several degrees to many of the new runabout transoms because of the increased hp these days thats being added even though the older ones were heavier. The hp increase and the four stroke ones seems to be a bit heavier with the four strokes less out of the hole guts. Normally after getting on plane we back the engines off too so that the boat handles nicely.

http://www.iboats.com/Transom-Wedge/dm/ ... w_id.40151
Image
Attachments
011.jpg

User avatar
BayouBengal
Posts: 1013
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BayouBengal » Sun Jun 13, 2010 8:41 pm

Foils mounted to the motors yells ugly IMO.
Agreed. And I wasn't crazy about putting the Smart Tabs on either, but now I'm kind of hooked on the smooth level always on plane ride that I get with them.

I'm not sure where I'll end up with this; but with due respect to Mr. Witt, if I were to build another Squirt, I'd slant the transom to around 15 to 16 degrees instead of the 12 called for in the plans. With that being said, I'll also say the boat performed fine with the lighter vintage Johnson 15 hp I had on it. It didn't run very fast and it took a while to get on plane with two adults, but there was no porpoising and no need to add any after market stabilizers. However, even the 15 hp was trimmed all the way in; so, once again maybe more angle in the transom would be helpful. Sounds like from your post this problem isn't limited to the Squirt design.

Oyster
Posts: 4408
Joined: Sun Jul 02, 2006 7:10 pm
Location: North Carolina

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby Oyster » Mon Jun 14, 2010 4:15 am

BayouBengal wrote:
Foils mounted to the motors yells ugly IMO.
Agreed. And I wasn't crazy about putting the Smart Tabs on either, but now I'm kind of hooked on the smooth level always on plane ride that I get with them.

I'm not sure where I'll end up with this; but with due respect to Mr. Witt, if I were to build another Squirt, I'd slant the transom to around 15 to 16 degrees instead of the 12 called for in the plans. With that being said, I'll also say the boat performed fine with the lighter vintage Johnson 15 hp I had on it. It didn't run very fast and it took a while to get on plane with two adults, but there was no porpoising and no need to add any after market stabilizers. However, even the 15 hp was trimmed all the way in; so, once again maybe more angle in the transom would be helpful. Sounds like from your post this problem isn't limited to the Squirt design.


my morning ramble.....
I don't get too excited about any power boat porpoising. There are hundreds of boats that have plowed the waters with the same issue being sold in the production setting market. The advantage of the boats that we build for ourselves is that we can actually tweak them or refine them for a better word without it showing to the average man on the street.

One of the reasons for the wedges being sold and the foils added to the market was that the production boats built in a mould continues to be recreated over and over while its very hard to change when deailing with a third party stamping the boats out.

But after saying that, most pointed bow boats rarely use 16 degrees transom and I personally would never suggest that extreme modifications for anyone. ON the garvey type hulls, yes start with a more angle. With the new woods such as the mahogany types woods, the wood alone weighs less.

If you add that we are using multiple engines and going faster these days as a rule with the total boat across all parts of it weighing less, in small boats maximum hull speeds can come into play causing some of these issues. We seem to address the transom issues even building them with more weight to accomadate for adding heavier engines or decorative woods and rarely consider the affects of the overall shifts in weight too. In small boats, there are some adverse issues and folks reading posts dealing with porpoising because of the out of trim thats caused rarely understands some of the "devil in the details" too. [I am only speaking in general terms from observing this across lots of forums]

We find a sweet spot and enjoy the boats while building another. :lol: In almost all cases when built properly, the boats will take more abuse than our bodies. Just because we have more throttle on the throttles, does not mean that we must use it.

As a example, my last build of a dory style hull I used a new state of the art E-Tec engine far suppassing the recommended power and performance because of the plus of having the guts when loaded. But when two people are in the boat, the throttle only sees 3,200 out of the 5,500 that the engine can turn when properly wheeled. I placed a warning label on the steering wheel cover using a small engraved plate. :wink:

Oyster
Posts: 4408
Joined: Sun Jul 02, 2006 7:10 pm
Location: North Carolina

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby Oyster » Mon Jun 14, 2010 4:58 am

One thing I will add seperately is that while I like the look and coolness of vintage engines to some of these builds, for me personally I boat in remote areas, self supporting and need to be able to depend on its readiness and readily access to parts because of my frequent use of any and all hulls. There are also areas of the country and even the world that has updated the guidelines that clearly defines the type of engines that can be used in certain regions such as lakes and rivers. So there are concrete reasons not to also use the older engines just from the standpoint of the EPA guildlines. Many of the new engines certainly will weigh differently and produce different hp and performance. This forces people to address their particular builds differently.

Most of the time in the build stage these types of issues are not thought about. When these and some other issues come to light is when you experience the boat in the water. So yes the launch phase of a boat is just another step in the process of building and making a boat usuable and optimum.

User avatar
BayouBengal
Posts: 1013
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BayouBengal » Mon Jun 14, 2010 6:07 am

So yes the launch phase of a boat is just another step in the process of building and making a boat usuable and optimum.
Right. I have people ask when I'm going to build another boat. Hell, I still haven't finished this one.

User avatar
BulldogBoater
Posts: 498
Joined: Wed Jan 16, 2008 9:16 pm
Location: Wilson, North Carolina
Contact:

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BulldogBoater » Mon Jun 14, 2010 6:50 am

Alan Blackwell built a 10' Outboard Squirt and had it in the water at the last Gathering. I did not discuss this topic will him but I did notice he had angled aluminum shims on his transom to increase the angle of the outboard. I am sure he would have only added the shims if he found a need for them. You might want to PM him. He built the boat several years ago and am sure he has tweaked to near perfection.

KB
"I'm not trying to get it perfect. I'm trying to get it finished!"
www.tubbytug.com

User avatar
BayouBengal
Posts: 1013
Joined: Tue Jul 31, 2007 7:29 am
Location: Baton Rouge, Louisiana

Re: Squirt with 25HP, Lots of bouncing, Trim Tabs?

Postby BayouBengal » Mon Jun 14, 2010 8:36 am

Bulldog, we actually had the pleasure of meeting up with Alan and his wife, Sherri, a couple of weeks ago. We met and launched together in Covington, LA and cruised the Tchefuncte River to Madisonville (about a 20 mile round trip). We looked at it as kind of a trial run to decide if we wanted to make the Chatanooga trip at the Gathering. I ran out of gas with about a mile to go to get back to the launch and Alan had to tow me in. I'd started with 4 gallons and was somewhat surprised at the amount of fuel consumption. Alan also started with 4 gallons and had probably a 1/2 gallon left. So if we're going to make the Chattanooga trip, we're going to need to probably need to find some gas on the way.

I seen and discussed his dampeners with him, they're smaller than mine, his are about 7 inches side to side and 4 to 5 inches fore to aft. Mine are about 7 inches side to side and about 7 inches fore to aft. His are also fixed in place while mine are mounted to a gas shock. Alan's boat didn't plane as quickly as mine and he appeared to be a little bumpier, but he was also much faster. In a nutshell, he's pretty much where I want to be, top speed of 25 mph with two adults, comfortable cruising speed of around 20 mph with less fuel consumption than I'm presently experiencing. I'll settle for a little bumpier ride to get there; I just need to find the right compromise between speed and ride.

Alan and I had wanted to share rides, but it began to rain heavily when we reached the launch and so we didn't get an opportunity to experience each others boats. By the way, I really look forward to meeting you and seeing your Squirt at the Gathering. Thanks for your input.


Return to “Speed and Performance”

Who is online

Users browsing this forum: No registered users and 2 guests