A question about "Porposing"

[Manduchi]

I need a little help please. I have a '79 Ranger 1850VS with a 150 HP Evinrude XP.<br /><br /> I have a huge problem with bow rise when I take off.<br /><br /> At a measly 8 MPH I cant see over the front of my boat. When I dump the throttle it takes a full 8 seconds for it to come back down and get on plane.<br /><br /> Any where between 15-40 MPH this thing is porposing so bad I have to put the foot feed for the trolling motor in a locker or it will fly around and hit some one.<br /><br /> I CANT GET A SMOOTH RIDE OUT OF THIS THING, unless Im going wide open throttle. Even then it porposes pretty hard 3 or 4 time before it smooths out.<br /><br /> It does this with 2 people in the boat or 4 people. I have even shifted weight, doesnt really help?<br /><br /><br /> Is this normal for a bass boat??? Is there any thing I can do to stop this.<br /><br /> This boat is completely useless to me if its going to ride like this.<br /><br /> Even on glass smooth water it does it?<br /><br /> I have trim, but it seems to be broke. It goes back to the down position under power.

 

[KCook]

Re: A question about "Porposing"

Fix that trim

 

[Texasmark]

Re: A question about "Porposing"

Manduchi, when you say it goes to the down position under power what do you mean? When you have an engine with tilt/trim the trim is like 20 degrees and the tilt is like 4 under and another 20 out. So, starting with the engine tilted up as far as it will go and coming down, you have 20 tilt, 20 trim, 4 tilt sort of thing.<br /><br />If you put too much power on the engine when in the tilt position, the pressure relief valve in the trim unit opens and the engine is pushed down to the max out trim position if you are above it, or to the max tucked in position if you are under it. The max tucked in position is where the lower unit jams against something in the motor mount.....like maybe a tilt bar if you have one.<br /><br />Is the lower unit parallel to the transom when you say it is in the down position under power?<br />---------------------<br />K Cook.....Hear you on that but I'm puzzled. If he is porposing that is indigitive of trimmed out too far. Also the time to get on plane being that long is the same thing......but he said he is tucked fully in? <br /><br />Confusing.<br /><br />Mark

 

[Manduchi]

Re: A question about "Porposing"

It goes all the way down, not just to trim.<br /><br /><br /> Its tucked all the way in...........<br /><br />I wondered if maybe it didnt have a power problem, But it goes 46-47 Mph on a dinged up 19 pitch prop????<br /><br /> I moved weight up front, it did help cut the plane time down. But it had no effect at all on the porpusing.<br /><br /> I have thought about getting a foil/stabalizing fin??? How much do you think it would help ??

 

[KCook]

Re: A question about "Porposing"

Point is, trim is essential to any high performance OB boat. Most certainly a bass boat. Maybe the trim is the issue or maybe it's something else. But you cannot be sure until the trim is 100% healthy.<br /><br />Kelly

 

[Silvertip]

Re: A question about "Porposing"

Forget the hydrofoil. First fix your trim. Then visit Nauticus.com to read about Smart Tabs. They are simply the best thing for boats since the outboard itself. You'll stay on plane at slower speeds and bow rise during hole shot will be greatly reduced. They will virtually eliminate porpoising and they are not terribly expensive compared to other marine stuff that adds far less to your enjoyment.

 

[fishingdan]

Re: A question about "Porposing"

A hydrofoil will typically cost you a good chunk of top end speed and often hide the problem. These devices will get you on plane faster. They add planing surface to the back of the boat and it gives the back of the boat more lift. The downside is that they typically add drag (unless you raise the engine). The thing I really don't like about them on a faster boat is that they can cause some nasty handling problems if you pull back the throttle (from high speed) to quickly. <br /><br />Porpoising can be caused by several things. It sounds like you have tried the quick and easy ones. <br /><br />1)Check mechanical stuff:<br /><br />- Make sure that the engine is correctly mounted. The anti-ventilation plate on the engine should be at the level of the hull bottom or above it. <br />- Check that the prop hub is not starting to slipping. <br />- Check to make sure the transom is solid<br /><br />2)Trim the engine all of the way down or in (depends how you look at it) when accelerating from a stop. <br /><br />3) Move weight around. Sometimes too much weight in the back of the boat can cause this. Other times, there is too much weight in the center of the boat. Try balancing weight (forward and back) by keeping it out of the center of the boat. A designer recently explained porpoising as a "pendulum". Too much weight at the center will cause some instability as the center of gravity moves back and forth with the movement of the boat. <br /><br />4) Check the hull bottom and make sure the last 4-6 feet (closest to the transom) of the hull bottom is straight. It should be perfectly straight. Start at the keel and work your weight out. Keep the straight edge parallel to the keel.

 

[Reel Poor]

Re: A question about "Porposing"

On the transom, at the base of the engine mount there is a row of holes. There may also be a pin installed in one set of these holes (penetrating from one side to the other). Note in the pic there is no pin visible. Make sure if there is a pin there, that it is installed in the lowest hole possible (nearest the transom). If not it will not let the engine trim all the way down which may cause porposing. <br /><br />

 

[Manduchi]

Re: A question about "Porposing"

I checked, there is a pin and it is in the lowest hole.<br /><br /><br /> I dont think the prop is slipping, The engine doesnt seem to surge at all??<br /><br /> I plan on getting a new prop so I can find out for sure then.<br /><br /> We tried shifting weight, the damn thing still bounced even with me sitting on the forward casting deck. I came about 2 feet off of the floor and fell onto the deck as the boat was bouncing back up. " This is some what painful"<br /><br /> I guess I will fix the trim and see if that helps. Then the prop.<br /><br /> But if that doesnt fix it I dont know what to do unless any body has any other suggestions.

 

[bryantjb3]

Re: A question about "Porposing"

I thought Reel Poor had it nailed. Is it possible that when you are applying throttle that your trim is not staying down? This would seem to have to be the case with that engine. Have you checked your trim cylinder fluid?

 

[Reel Poor]

Re: A question about "Porposing"

With the boat on the trailer and the motor all the way down does it touch the pin previously mentioned?

 

[Manduchi]

Re: A question about "Porposing"

I cant put it all the way down, It will hit the pavement.<br /><br /><br /> Wont even come close to getting all the way down before that happens.

 

[Reel Poor]

Re: A question about "Porposing"

Maybe by letting the tounge of the trailer down to the ground will allow enough room to trim all the way down.<br /><br />Are their any shims between the transom and the engine bracket? If so, how are they installed? Wide ends vs thin ends. Wide end or thin end up?

 

[WillyBWright]

Re: A question about "Porposing"

Rangers are designed for speed. With Bass Boaters, there are just two speeds. Slow-No-Wake and Full. The hydrodynamics of that hull were designed for top speed. Designs are better now, but 1979 was pretty much the dawn of Bass Boat time. Forrest Wood was mostly interested in speed and getting to the fishing hole first. The hull is designed to hold the bow down with speed. The porpoising won't go away unless the boat is running at 3/4 throtte or more. If you must run slower, look into trim tabs.

 

[LubeDude]

Re: A question about "Porposing"

Originally posted by WillyBWright:<br /> Rangers are designed for speed. With Bass Boaters, there are just two speeds. Slow-No-Wake and Full. The hydrodynamics of that hull were designed for top speed.

Poppycock!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! <br /><br />There is something wrong, and I say that the engine isnt going all the way down. You can even pull the pin and let it down even farther. I dont have a pin in mine.

 

[Texasmark]

Re: A question about "Porposing"

Been watching the ball batted back and forth. <br /><br />I just can't imagine a porposing, especially extreme porposing, situation with the engine tucked all the way in, and to boot, a load on the front seat. Hole shot should be superb and the bow would plow which would not let you experience your full mph potential, but porpose?<br /><br />And to add confusion, 47 mph on a 18.5 Ranger with a 150 @ 19" sounds right on (checks with the prop calculator also).<br /><br />Then, after going over this several times I just realized the year ('79) and the comment about Forrest and speed. I know that when you are trimmed out and going too slow you will porpose....increasing speed or tucking in is the only way out. You are tucked all the way in. So as Willy said, soulds like your problem is "pedal to the metal".<br /><br />So, why don't you fire off an email to the folks in Flippin, Arkansas, and ask them what you can do to stop it. Surely the guys at the factory figured out how to combat it years ago.<br /><br />Mark

 

[brownies]

Re: A question about "Porposing"

I had a 77 Ranger that would do the same. Had to remove the pin and trim the motor ALL the way in/down in order to get it to take off. <br /> After the boat was up on plane, I could trim the motor out/up, but, just a quick "bump" or two of the button before it would start porpoising.<br /> There was very little trim adjustment available on that boat.<br /> The best improvement I made to it was to install a hydrofoil. It was cheap, made the boat plane at slower speeds, kept the bow down on launch, and, set the stern down slower when stopping. No noticable speed difference, but, that's been many years ago and no GPS.<br /> Some people hate hydrofoils, but, I've liked them on every boat I've had...and I liked the price and durability.

 

[POINTER94]

Re: A question about "Porposing"

Not really my area but wouldn't a jack plate moving the engine further back solve this problem? Depending on the model used you can further adjust the depth the prop is in the water vertically not just on the end of the tilt "circle".<br /><br />Smart tabs or trim tabs would also serve to reduce this effect.

 

[cart7]

Re: A question about "Porposing"

I used to own one of those 1850's for a couple years, they were pigs. Then again, a lot of so-called high performance bassboats back then were pigs, or at least, very weight and trim sensitive.<br /><br />First things first, fix the trim. No point in spending money on "fixes" until you get one of the basics taken care of first. Then get back to us.<br /><br />BTW, it's not uncommon for a high performance boat to squat stern low on the takeoff, to the point where you can't see over the bow. That's a result of a heavy engine, batteries, fuel and two anglers towards the rear of the boat and nothing towards the front.

 

[Manduchi]

Re: A question about "Porposing"

Okay,<br /><br /><br /> I pulled the pin out and I installed a fin.<br /><br /> An "SE 300" It was the bigest one I could find.<br /><br /> If it warms up I will give it a try this week end.<br /><br /> I checked my trim fluid, It has plenty.<br /><br /> Im thinking it might be a valve leaking???<br /><br /> If the pin and foil dont help, I guess I will have to put it in the shop.