50hp, 19pitch, new tach..... works great.

[michaelj1978]

Well I finally had the dealer put on a new tach as some of you said the 19pitch prop would be too much for my 50hp evinrude (1995). <br /><br />Took it out this weekend with 10 gallons of gas, 400lbs of people and probably 200lbs of gear. Boat is an 18ft flat bottom jon with a fully finished interior.<br /><br />The old tach was reading over 7,000rpm no matter how it was adjusted on the back. The dealer hooked up the new one and wide open throttle was giving us 6,000rpm with the motor tilted up a few inches. With the motor fully down in the water pushing the front end down we were right at 5,000rpm. At 6,000 when the front end wasn't pushing, we were running around 29mph. <br /><br />I know some on here had said before that that prop wouldn't push my boat, but appearently it does, and does pretty well. <br /><br />I'm even tempted to raise the motor one hole and see if that can help get the front end of the boat out of the water more and see if that changes anything. If nothing else I can drop it back, but I'm pretty happy with how it ran compared to how it used to run with the 15pitch prop. The 15 used to get us to about 20-21mph then start to ventilate and overspin. The 19 doesn't do that unless you intentionally raise the motor up too much.

 

[ob15]

Re: 50hp, 19pitch, new tach..... works great.

That's great! Gald to see you got things figured out. I definitely need a 19" pitch prop on my 89 50.

 

[Dhadley]

Re: 50hp, 19pitch, new tach..... works great.

Well, youre headed in the right direction but youre still well over 30% slip at 6K with a 19.

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

As dhadley says, somethings not right if your getting 6000 rpm and 29 mph from a 19 pitch prop. That is way off, are you sure its a 19? If it is it must have no cup or is damaged and is horribly innefficent. As I stated before I get about 34 mph at 6000 from my 15 pitch.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

it's a 19, brand new, cupped, and no damage...<br /><br />It's a 1995 50hp and I believe the gear ratio is 2.42:1

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

according to my prop calculator at a more reasonable 15% slip you should be getting 38 mph. What are you using to measure speed? Either you are going faster than you think or your prop is slipping badly and you have some setup issues that dhadley or other expert needs to help you with.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

I'm using an Eagle 320 with GPS. It displays mph to the tenth of a mph. 29.1 has been the top speed so far. <br /><br />As for the setup, we tried lowering the motor all the way onto the transom and all that did was make the front end of the boat press against the water and we had water shooting out the sides and a hard time getting front end up. This setup left the "fin" that is on the engine about an inch below the bottom of the boat. It also made it difficult to raise the motor when at speed, because that fin hit the water and just kicked it up, spashing it all over the engine.<br /><br />The current setup keeps that fin right in line with the bottom of the boat and the water doesn't begin to kick up until the motor is tilted way up. With it at this height and the motor all the way down, I can get it to 5,000rpm at wide open throttle, (the nose is still pushing water) and then gradually tilt the motor up, which makes the nose come up and a faster speed (top speed) can be reached right around 5,900-6,000rpm. The motor sits about 1 inch above the transom.<br /><br />I'm thinking that if I raise the motor up one more notch that under wide open throttle and the motor tilted down it won't push as much water in the front, and that I would have to tilt it up less to achieve the top speed.<br /><br /><br />As far as "setup" what are you referring to? What else can I do to the boat/motor to make it run better or faster? The only thing I know of is to raise the motor up or down a notch and play with the tilt button to get the right setup. <br /><br /><br />What am I missing?

 

[Silvertip]

Re: 50hp, 19pitch, new tach..... works great.

I have the same engine but on a Alumacraft Navigator 165CS. As everyone is pointing out, something is very wrong with that setup. You are trimming way too high or as previously indicated, the prop is terribly inefficient, the tach is still set wrong or the speedometer you are using is not accurate. The RPM/prop pitch/Speed simply don't compute.

 

[ob15]

Re: 50hp, 19pitch, new tach..... works great.

You may want to take the fin off & try running with out it.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

It's the metal fin on the motor, not an accessory or anything like that. It's about5-6 inches wide.

 

[ob15]

Re: 50hp, 19pitch, new tach..... works great.

Sorry, that's the antiventiltion plate.

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

Setup refers basicly to raising the motor to its optimum height and trim levels. You are on the right track to raise the motor more. DHadley or others please correct me if Im wrong, but I think you have too much prop. Trimmed down you are only turning 5000 rpm and it seems that when you trim up high enough to get 6000 you arent getting the speed you should, which means you are probably having to trim so high to spin the prop you are ventilating the prop and losing thrust. Maybe your boat is light enough to get by like this and if you get the motor high enough you can compensate somewhat for this. Just be careful of water pressure.

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

Setup refers basicly to raising the motor to its optimum height and trim levels. You are on the right track to raise the motor more. DHadley or others please correct me if Im wrong, but I think you have too much prop. Trimmed down you are only turning 5000 rpm and it seems that when you trim up high enough to get 6000 you arent getting the speed you should, which means you are probably having to trim so high to spin the prop you are ventilating the prop and losing thrust. Maybe your boat is light enough to get by like this and if you get the motor high enough you can compensate somewhat for this. Just be careful of water pressure.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

So try to move it up another notch? This will make the antiventilation plate sit about an inch higher than the bottom of the boat when the motor is trimmed all the way down.<br /><br /><br />What do those big fins do? Would one of those possibly help?

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

I run with my av plate about 4 inches above the bottom, but this is extreme and I only do it for shallow water use, and my water pressure is marginal. An inch should be ok and should help. The hydrofoil fins are mainly to help on takeoff and should be out of the water at speed. Also, make sure you dont have too much weight in the front of your boat causing it to plow.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

Before I get it back out next weekend I'm going to raise the motor up 1 notch, approx. 1 inch.<br /><br />I'm also going to bondo all the dings on the bottom of the boat and sand smooth. I think that is causing some problems too. <br /><br />A few years ago the boat didn't set on the trailer right, between that and a few stumps we've run over the bottom near the transom has some dings and dents that are up to 2 inched deep. <br /><br />Bondo works on aluminum right? Just scratch it up, apply and sand? I've used it on metal and plastics.<br /><br />How's it hold up in water? I'll probably prime it grey anyways to match the boat.

 

[ddaigle]

Re: 50hp, 19pitch, new tach..... works great.

You may have created some serious hull problems with the trailer and stumps. I had a bad hook in my boat from the same things. A hook will really rob speed and keep the front end from coming up like it should when planing. I had to remove the flooring and hammer the really bad places out. I dont know if bondo will hold up on a boat bottom. I doubt it, but hopefully somebody else knows.

 

[michaelj1978]

Re: 50hp, 19pitch, new tach..... works great.

I was thinking either that, or having metal plates welded in between the ribs where it's dented and then sanded so they are as flush as possible.