79 OMC 150 on an 88 Glasstream Hydrobass 17v

[Thompy_04]

Maybe wrong forum but it is prop related. I'm using a Turbo 24 pitch prop and only turning 4500 rpm with a light load, some gear very little fuel, livewell water. I don't think I'm down a cylinder and this boat is pretty light I thought it would turn the 24. 6" manual jack plate and the motor is all the way up on it. Can I raise the jackplate on the hull at all or should it be flush with the transom?

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Raising the jack plate would depend on the type of plate.pics may help.
Answer the stickys at the top of the prop forum.
Do you know your gear ratio? What is the gps speed at 4500?

 

[Thompy_04]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v


Here's a photo of the set up I've moved the engine up on the jackplate and the JP is as high as it will slide. Can I actually move the plate itself up a couple holes on the hull? I get around 25 psi at wot now as well.
Prop is a Turbo 1 14 1/2 x 24 turning 55 mph at 4500 rpms. Boat weighs around 1400 fully rigged 1.85:1 gear ratio.

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

I'm no pro on a jack plate but it looks like it would be a little precarious.
Has the transom already been modified?
Your numbers don't add up. At 4500 you really can't do 55 It would be less than 1% slip.
Typical slip is about 8 to 12%
Is the speed by gps?
I would suspect the tach and the speedometer.The gps speed would eliminate the speedometer.
If speed is accurate;using 12% slip the rpm would be about 5100.

 

[Thompy_04]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

No modded transom, jackplate came with the boat. The speed was via GPS but I do have my doubts on the tach sometimes but it works great.

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

The tach is not accurate So your motor is running at about 5100.
HP is rated at 5000.I don't know the range of the 150 but but usually would be about 4500 to 5500.
Are the motor mount holes on the motor maxed out on the jack plate?
Do you experience any ventilation(cavitation) in normal operation?

 

[Thompy_04]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

None of the above. I searched the jack plate online and it's on backwards. I measured the the pad to prop shaft and it's 5.5" under pad, I've read to start at 3.5". I'm also as high as the j/p can go and up all three holes on the motor. With that raise I'm going to gain should I be looking at a bigger pitch prop?

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Are you saying you raised the motor or you just measured the setup.
Your prop selection would depend on your results. Without an accurate tach you can't tell about your results.
If your motor proves to be at 5100 on an accurate tach you wouldn't go to a higher pitch.

 

[Thompy_04]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Haven't raised it yet on there like I bought it, I just measured prop shaft to pad. If I raise the motor up to 3.5" under pad from 5.5" I should have to go up in pitch correct? How many RPMs do you usually gain raising motors up?

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Again I'm not well acquainted with jack plates and pads. I believe results will vary and you may need more prop.
But the results will determine that.If my estimated/ guess is correct you have about 400 rpm to spare.
Assuming your slip numbers remain within range you may not need a prop change.
Keep in mind the 3 1/2" is a starting point. If you start getting ventilation there may be a prop selection that allows you to remain at that height.The severity may indicate the best solution. I don't know if the Turbo1 is the prop for that.
Hopefully a prop guru will chime in with some more educated information.
You might pm some of the more informed contributors ask them to check your thread.
By the way from my limited research 55mph is impressive.

 

[dazk14]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Your getting way ahead of yourself talking about props.

Your jack plate is installed backwards, meaning setback but no jack. With the angle of the transom and setback, you are effectively buried deep.

The jackplates smaller, inside piece mounts to the transom.

Pull it apart, mount it properly (seal hull bolts) and you'll be looking at lots of vertical height adjustment (5"#).

Keep a log book and hit the water for testing.

You have pump pressure, so start where you like - it's easily adjustable. Generally lower to begin, since it's a bit easier to dial in on the way up.

Obviously, verify your tach readings.

Spike is correct, Glasstream's "Hull speed" usually tops out at 50mph and that is off a cliff.LOL although I did think Glasstream had a nice idea with all metalflake boats in there lineup.

Post back with your results. Should be fun.

Edit - oh ya, your water supply to the muffs is a bit kinked.

 

[Thompy_04]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Check on the hose. Old photo actually. Will post replies when the weather turns and I can do some work. Silicone fine for sealing the transom bolts?

 

[steelespike]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Again not acquainted with jack plates and transom modification.If silicone seems to adhere to the transom material I would use it.

 

[dazk14]

Re: 79 OMC 150 on an 88 Glasstream Hydrobass 17v

Check on the hose. Old photo actually. Will post replies when the weather turns and I can do some work. Silicone fine for sealing the transom bolts?

Marine silicone, ok. 3m4200 better.
I forgot to mention, very nice hull on the hydrobass.