Need. More. Speed.

[Tail_Gunner]

Re: Need. More. Speed.

Here found some old pics. The first is a volvo i/o...... i/o's run very deep so much so people rebuild there boats to get them higher...That cav plate is 1" above the keel maybe 1..1/2"

As you can see your drive is about 1-2 inches lower than that I/O and that casues drag or should... Well nothing is certain in this world but its highly likely your leaving 3-5 mph on the table... There ive chummed the water's...

https://encrypted.google.com/#hl=en....,cf.osb&fp=2cc4558067cc4a47&biw=1366&bih=620

 

[Tail_Gunner]

Re: Need. More. Speed.

Heres a better look ..i would have just edited that pic out but for some reason every time i try to edit a pic the comp freezes...sup with that admin

 

[QC]

Re: Need. More. Speed.

Typical . . . your computer freezes and it's somehow iboats' fault Heck, may be . . .

I am wondering if you are suggesting that the OP find some way to fix that?

Upside of a low X dimension (what that's called) is better prop bite and also less chance for blowout in corners and high trim positioned. The downside is what TG has referred to.

 

[Tail_Gunner]

Re: Need. More. Speed.

Typical . . . your computer freezes and it's somehow iboats' fault Heck, may be . . .

I am wondering if you are suggesting that the OP find some way to fix that?

Upside of a low X dimension (what that's called) is better prop bite and also less chance for blowout in corners and high trim positioned. The downside is what TG has referred to.

Well with all these tweet this follow that im sure opps and different browser's ...Yup iboat's fault......

Yes all he has to do is raise his motor.....That does come with some work and no garauntee's but im sure he will benefit from it...And keep raising it until it does blow out...or cavitate. Think about it 120 OB doing fourty..My little I/O does that with a 3.0 4cyl maybe a 100 at the prop.

 

[Circles47]

Re: Need. More. Speed.

OK.....................I think my motor has 5 mounting holes, and it's in the middle hole. Are you saying I should try moving the motor up one hole and see how it does? It already cavitates on a tight turn at WOT, would this make it worse? What all is involved with raising an outboard motor? Lot's of questions....................

 

[QC]

Re: Need. More. Speed.

BTW, due to the pic, I was thinking I/O. Never mind my comments about how to move up :facepalm:

It already cavitates on a tight turn at WOT, would this make it worse?

Yes, going up would typically make this worse. And, for clarity, what you are experiencing is actually ventilation.

 

[Tail_Gunner]

Re: Need. More. Speed.

Hold on a minute lets think about this for a minute...a few known's when i turn my old tub's turn hard you what happens i slow down dramactically for some reason i cant turn on a dime at 50... So i slow and turn a graceful arch or what feels like a graceful arch...maybe not so graceful. Good thing to if the boat would turn hard at 50 there goes the day wet wallet and all. Think about itdo you want your boat to be running on high plane and turn hard?

Id would suggest you lift it one notch at a time and and track the results,,,how hard is the turn...is it practical to turn that hard and fast..Or are does the prop blow out on slight turns. By raising the engien you should experience higher speed's and maybe increased hole shot and still be able to turn at respectable angles at respectable speeds...

Actually raising the engine to its most effecient height would be the right thing to do. From there...there are prop's that do well running on the surface and do not blow out..There is also something called a setback plate..with outboads you have a lot of option's to choose from and there yours to choose. But you have to first raise the motor and see if you have gain's...Just a thought...

 

[Circles47]

Re: Need. More. Speed.

Actually raising the engine to its most effecient height would be the right thing to do. From there...there are prop's that do well running on the surface and do not blow out..There is also something called a setback plate..with outboads you have a lot of option's to choose from and there yours to choose. But you have to first raise the motor and see if you have gain's...Just a thought...

I understand what you're saying here, but I'm just trying to figure out how to successfully manhandle an outboard motor nearly 6 feet tall and 400 lbs! I guess I'll have to decide if its worth it or not. I assume that the only thing holding that motor to the transom are 4 bolts?

 

[Tail_Gunner]

Re: Need. More. Speed.

Yes..go to the ourboard section and ask for ideal's...Trust me some of these guys are innovative and some plum crazy..Yes i believe its worth it...that should be a 45mph boat..and yes 4 bolt's.Hmm you have a hydrualic jack some place that would make short work of it..Time's like this makes me smile about my I/O..

 

[Circles47]

Re: Need. More. Speed.

Thought I'd do a brief update. I have a lifting ring and chain hoist on order, and have decided to raise the motor 1 hole (about 3/4") and see if it makes any top end difference. I'll let you know what I find out.

 

[steelespike]

Re: Need. More. Speed.

I've never done it but I've heard you can stabilize the trailer gently set the skeg on a block of wood;carefully remove the through bolts loosen the guide bolts and and raise or lower the tongue till the motor is at the height you need. Seems easy enough. lol

 

[Circles47]

Re: Need. More. Speed.

I've never done it but I've heard you can stabilize the trailer gently set the skeg on a block of wood;carefully remove the through bolts loosen the guide bolts and and raise or lower the tongue till the motor is at the height you need. Seems easy enough. lol

Sounds easy, doesn't it? Be my luck it would end up on the floor with me under it!

 

[Tail_Gunner]

Re: Need. More. Speed.

Thought about this for awhile. One could just build a cage of 2x2's that fit under the cav plate..little hydraulic jack and up she goes. Remeber its still balanced of the transome it just needs some vertical lift.

 

[Circles47]

Re: Need. More. Speed.

Steelespike, just re-read your last post. Were you trying to make a distinction between through bolts and guide bolts? My bolts seem to be all through bolts.....no slots or anything on the motor mount.

 

[Circles47]

Re: Need. More. Speed.

**UPDATE**
Received the lifting ring and the chain hoist I had ordered, so after work today, I raised the motor one bolt hole (about 3/4"). The lifting ring and chain hoist worked well, and I was glad it did, as I was doing it by myself! I centered the motor directly under the chain hoist hook, and lowered the tongue of the trailer as far down as possible with a hydraulic floor jack. I then hooked up the hoist to the lifting ring, and raised the hoist just enough to put tension on the motor. I was a little apprehensive when I removed the 4 bolts, but after wiggling it to loosen the silicone between the motor mount and the transom, it separated only about a 1/2 inch. I had not unhooked the steering cable or anything else, so the motor had nowhere to go. I used a razor blade scraper to remove the old silicone, cleaned it up real good, raised the motor to the next bolt hole, sealed around all 4 holes with new marine silicone, inserted the bolts, tightened everything up, released the tension on the chain hoist, and....taa daaa! All done, and less painful than I imagined.

I hope to head to the lake this weekend and try it out.

 

[Circles47]

Re: Need. More. Speed.

Ok, I THINK this is my last test! I took the boat to the lake today to try out new motor height, and left the lake with some perplexing questions. As posted before, I had raised the motor 3/4", and today it was me, my daughter, and my son testing the performance. The lake was calm, with very little wind. I detected very little difference in the boats performance from the last motor position. Holeshot was good, planing speed good, rpm's about 5100, and top speed around 40 mph. Motor had no more ventilation issues than it did before.....still have to trim down in tight turns....but always have. Normal turns do not ventilate. Propeller slip at 8%.

Now this is where it gets perplexing to me. Half way thru the test, I filled the rear live well with water to simulate my wife's weight, and in doing so, seemed to pick up 1 mph. That didn't make much sense, so I emptied the live well, dropped off my daughter at the dock, and figured that with just me and my 8 year old son, I'd pick up a couple more mph. Wrong. Top end struggled to even reach 40, and my rpm's appeared to drop closer to 5000 than the previous 5100.

I always thought that more weight resulted in more prop slip, which resulted in less mph??

Any thoughts on this?

 

[QC]

Re: Need. More. Speed.

If the weight in the stern allowed you to trim the bow higher then I can make some sense out of that.

 

[Circles47]

Re: Need. More. Speed.

If the weight in the stern allowed you to trim the bow higher then I can make some sense out of that.

I don't think trim is the issue....I could trim higher if I wanted to, high enuf to bounce the front end.

 

[QC]

Re: Need. More. Speed.

They are usually fastest right as they start to porpoise. Extra stern weight can impact this. Weight is rarely good, but there are exceptions.

 

[Circles47]

Re: Need. More. Speed.

Seems like everything about my setup has been an exception!