Jump to content
  • GUESTS

    If you want access to members only forums on HSO, you will gain access only when you Sign-in or Sign-Up .

    This box will disappear once you are signed in as a member. ?

Increasing boat speed


jparrucci

Recommended Posts

I have an early 90's forester 14.5 footer that is pretty deep and wide. I have a 2007 mercury 2 stroke 25 horse on the boat now. How with me alone hits about 22 mph in calm conditions. When a have the dog, livewell, gas and another person I can barely get 18 mph. I am on lake vermilion and put in lots of miles. Outside of buying a new motor, is there any other options? I have adjusted the tilt a few times, but I then have issues with keeping the motor in the water. It does not have power tilt. I am less concerned about the hole shot and more concerned about top end speed, although I do not want to over rev the motor. Do they make performance parts? A new prop? Power tilt? Or am I looking at a bigger motor? Current motor is not oil injected and I am sick of mixing oil and gas, so there is at least another plus for a new motor. Boat is rated for a 40, although the newer 40 four strokes are probably too heavy. A 30 four stroke that is oil injected and has power trim would be awesome, but they are hard to find, especially used.

Link to comment
Share on other sites

FWIW - you probably already have, but getting rid of weight will help, and so will moving more of what weight you do have as far to the rear of the boat as you can, without porpoising, etc.

We have a 16' boat with a 50hp (old ratings) and no power trim. What we found helped with that boat was adding a hyrdofoil. This allowed us to raise the trim setting pin one extra hole, but it kept the boat from porpoising at that level when we had less weight in the boat. It maybe slowed us down in overall top speed under perfect conditions, but it made it better for the varied amounts of people/weight we would add to the boat. Just more consistent overall, and totally less "bumpy". Poor mans trim tabs wink

On the repowering front, in that sized boat, if you want speed/performance but still get better fuel economy, I think I would go with a 40 e-tec. Not quiet the quiet of a 4 stroke but much better than many/most 2 strokes in that range, and very good on fuel, while having the most punch you will find in a 40, IMHO.

I personally would NOT put a 4 stroke on your rig if you wanted any sort of performance. And I am saying this as I am buying a 60 4 stroke, but that is going on a pontoon smile

Good luck!

btw - you won't find a 4 stroke that is oil-injected wink

Link to comment
Share on other sites

I would assume you could get a prop with a larger pitch size. But they may also harm your hole shot if you are lacking now.

A decrease in your prop pitch that you are using now would give you a better hole shot.

If you do not have a tach, then that is a risky move trying to gain speed by going over the recommended rpm's for your motor.

A higher hp motor may be the ticket for you to increase the top end speed.

Link to comment
Share on other sites

Could add hydrofoils to your cavitation plate. I used a 25hp on a Lund 16 Rebel and noticed a little better performance after putting them on. Even so, if I put three people in the boat, it struggled to plane up.

Link to comment
Share on other sites

Go with Harvey's advice. Buy a second prop with larger pitch. When you've got dog/gear/passengers throw on the larger pitch prop. When it's just you then use the current prop or be very cognitive of not over-revving the engine. Swapping props takes all of a minute or two and probably a needle nose pliers.

Power trim won't do you any good since you need to keep the motor trimmed all the way out regardless. Power trim would only help you get on plane faster (trimmed down) and then you would trim all the way out anyway.

I also wouldn't put a 4-stroke on there. Your problem is speed and weight is your big killer. Hanging a heavier 4-stroke on the back doesn't help even if you increase hp. Stick with 2-strokes and find ways to decrease the weight in your boat:

-Do you need to have a battery?

-Drop a few pounds yourself

-Toss the dog overboard

-Too many electronics?

-Keep your livewell filled with only enough water to keep something fresh...you don't need those fish to live all that long!

Link to comment
Share on other sites

I have 1 prop I use when I have 1 or 2 in the boat but if I have 3 and alot of gear, then I go down one pitch in the prop size and that really helps getting up on plane and not much for loss in top end.

Propr can really change how the boat performs as long as one is not going way over the recommended rpm's for the motor.

Link to comment
Share on other sites

Couple things to be sure of first.

Is the shaft length and transom the same? Is the engine already operating in the recomended rpm range? Is the weight distributed evenly in the boat?

If yes, then, In all reality, youre going to gain little by increasing pitch. If you do that and add the people/weight to the boat, you may very well have difficulty getting on plane and may only gain a mile or 2 in speed. Right now, you are a little over half of the maximum hp for that boat and from the sounds of it, you may be somewhat close to the max weight for the boat.

Link to comment
Share on other sites

Could add hydrofoils to your cavitation plate. I used a 25hp on a Lund 16 Rebel and noticed a little better performance after putting them on. Even so, if I put three people in the boat, it struggled to plane up.
No, a hydrofoil will take away from top speed. The hydrofoil adds more drag.

Only use a hydrofoil to help the boat get up plane faster. Even then it does not always work.

Link to comment
Share on other sites

Regarding pitch...

Is your motor lugging? If so, less pitch.

Is it over revving? Is so, more pitch.

Is it just right? Leave pitch alone, make other adjustments.

Regarding trim (you called it tilt, trim is the correct term. Tilt is when you move the motor up out of the water) Trim the motor up until it starts to porpoise, then back down a touch.

Keep in mind that;

-load weight

-load position

-wind

all affect where the trim needs to be for max performance. Try to adjust the trim so you can always be safe.

If you have done all that, the next step is more power.

I am not aware of any performance parts for outboards. If you are a gearhead, there are internal motor tweaks that you can do.

I think you should get a 40 hp, with power tilt and trim.

Link to comment
Share on other sites

Quote:
No, a hydrofoil will take away from top speed. The hydrofoil adds more drag.

It may add some drag but it also adds lift allowing you to trim out your motor a bit more. I do know that my rebel gained about 2mph on top end after I installed the hydrofoils and trimmed the motor up. I have them on my existing motor. This one has power trim and maybe I'll play with it this summer to see what happens. Could be a fun experiment.

Link to comment
Share on other sites

How with me alone hits about 22 mph in calm conditions. When a have the dog, livewell, gas and another person I can barely get 18 mph.

Just to put that in some perspective... Lets say you've got 18 miles worth of travel and lets forget about acceleration time just to make it easier.

If your boat is going 18mph it will take 1 hour.

If your boat is going 22mph it will take 49 minutes.

If your boat is going 25mph it will take 43 minutes.

if your boat is going 30mph it will take 36 minutes.

Personally, I would just live with it or get a bigger motor.

Squeezing out an extra couple of miles an hour would be great, but what is the cost/benefit.

Link to comment
Share on other sites

I understand your point Bobby, but cost/benefit analysis of a fisherman is not a good way to look at things. We are the ones that spend $20,000 on a boat, $30,000 on a truck to pull the boat, a few thousand dollars on rods and tackle... all when we could go the local fish market and pick up a few pounds of fish for a few dollars. Perspective? Pshhhh

Link to comment
Share on other sites

Thanks for all the replies. The motor is a long shaft and mounted as deep into the water as it goes. A couple of extra mps doesn't seem like much but vermilion is a big lake and it is not uncommon for me to run 40 miles in a day. My brother has a bigger boat and will break the waves out in front of me on windy days, bit he has a hard time doing that at the speed I am going. A hydofoil might be an option. Another level of trim makes a huge difference in my speed, but if I can keep the motor in the water better it might be an option. I will upgrade to a larger motor at some point. But it is not a financial move I am willing to take right now.

Link to comment
Share on other sites

Just to put that in some perspective... Lets say you've got 18 miles worth of travel and lets forget about acceleration time just to make it easier.

If your boat is going 18mph it will take 1 hour.

If your boat is going 22mph it will take 49 minutes.

If your boat is going 25mph it will take 43 minutes.

if your boat is going 30mph it will take 36 minutes.

Personally, I would just live with it or get a bigger motor.

Squeezing out an extra couple of miles an hour would be great, but what is the cost/benefit.

Higher speed means more fun too cool
Link to comment
Share on other sites

Thanks for all the replies. The motor is a long shaft and mounted as deep into the water as it goes. A couple of extra mps doesn't seem like much but vermilion is a big lake and it is not uncommon for me to run 40 miles in a day. My brother has a bigger boat and will break the waves out in front of me on windy days, bit he has a hard time doing that at the speed I am going. A hydofoil might be an option. Another level of trim makes a huge difference in my speed, but if I can keep the motor in the water better it might be an option. I will upgrade to a larger motor at some point. But it is not a financial move I am willing to take right now.
Since this is a low HP application, I might be wrong (already have been once in this thread), but raising the motor may free up some speed. To be clear, not the trim, but raising the mounting of the motor. Too high and it will cavitate, but too low adds drag with no benefit.
Link to comment
Share on other sites

Thanks for all the replies. The motor is a long shaft and mounted as deep into the water as it goes. A couple of extra mps doesn't seem like much but vermilion is a big lake and it is not uncommon for me to run 40 miles in a day. My brother has a bigger boat and will break the waves out in front of me on windy days, bit he has a hard time doing that at the speed I am going. A hydofoil might be an option. Another level of trim makes a huge difference in my speed, but if I can keep the motor in the water better it might be an option. I will upgrade to a larger motor at some point. But it is not a financial move I am willing to take right now.

Perhaps your prop and unit is buried too deep, causing drag, losing speed. Let's say its true, I can't imagine being more then a few mph. I say a hydrofoil and jackplate will put with gaining extra mph but can you justify the cost for extra mph. That boat and hp has reached its limits and full potential, live with it.

Link to comment
Share on other sites

I was in the exact same spot, JP, with similar performance #s on my 14 ft boat with a 25hp 4 stroke. After hydrofoil and losing 2" of pitch, I GAINED top-end to the tune of about 2 mph and had a much easier time planing.

Then I finally went for the 40hp etec. Now I can load the boat full up and I don't lose any speed, with very little loss of hole shot. Basically, at max HP and 2 stroke, I gained 4 mph with just me and 8 mph fully loaded.

A big lesson here- horsepower is for acceleration, not top speed.

Link to comment
Share on other sites

I was in the exact same spot, JP, with similar performance #s on my 14 ft boat with a 25hp 4 stroke. After hydrofoil and losing 2" of pitch, I GAINED top-end to the tune of about 2 mph and had a much easier time planing.

Then I finally went for the 40hp etec. Now I can load the boat full up and I don't lose any speed, with very little loss of hole shot. Basically, at max HP and 2 stroke, I gained 4 mph with just me and 8 mph fully loaded.

A big lesson here- horsepower is for acceleration, not top speed.

Sounds like you could use more pitch.
Link to comment
Share on other sites

Two of you got increased top speed with the hydrofoil? Hmmmmmm. Was this low HP applications for both of you?

Yes it was. Very similar situation to the OP where I was under-powered. As I posted earlier, I had a 25hp on a 16 Lund Rebel rated for 45hp. With just me in the boat it worked fine but add another full-size adult and I struggled to plane out. Added the hydrofoils and I could get up on plane with two additional passengers plus with the added lift it gave me, I was able to trim it out one more notch and my top end speed gained a small amount, like Harvey, about 2mph give or take.

The boat I have now is rated for 90hp and that's what I use on it. I have hydrofoils on it because they were with the boat when I bought it used. I’ve always been under the impression that hydrofoils can help when you are under-powered but don’t really do much when you are sufficiently powered. I might try experimenting with it this summer to see what it does. I will not be surprised if I actually gain top end speed when I remove them.

Link to comment
Share on other sites

Join the conversation

You can post now ↓↓↓ or ask your question and then register. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Privacy Policy. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.