can any one help me to understand

[trendsetter240]

Re: can any one help me to understand

hello i have a 1996 larson hantom with a 5.7 mercruser I/O with and alpha one on it i have a 15 X 19p aluminum prop 3 blades today it was really nice day,lnice and flat so i tested the speed of the boat @ WOT my gps gave me 38.9 MPH @ 6000 RPM i had a full tank of gas and it was just me and my girl in the boat i was not able to hit more then 38.9 my Q? is now what type and what size prop will be good over all for my boat also i know-this when i am going at slow speed in the inter coastal i travel at 3000 rpm and the boat feels like is dragging

Do you know the gear ratio of your Alpha One drive? If it's the 2.0:1 Alpha and your GPS is showing nautical miles per hour then everything makes sense and you need a higher pitched prop.

 

[mannydvk11]

Re: can any one help me to understand

I would turn that selector back and forth a couple times, like Tailgunner said, just in case the switch is not making a good connection.

Out of curiosity, what RPM does the tach say your engine is idling at?

i will try that and the tach show 800 to 900 on idling

 

[mannydvk11]

Re: can any one help me to understand

Do you know the gear ratio of your Alpha One drive? If it's the 2.0:1 Alpha and your GPS is showing nautical miles per hour then everything makes sense and you need a higher pitched prop.

i was using the iPhone with the navionics app and my garming gps

this is the settings on the phone

 

[H20Rat]

Re: can any one help me to understand

i will try that and the tach show 800 to 900 on idling

idle rpm should be at 650... Your tach is reading high. Even if the switch shows the correct position, you may have a defective one.

 

[mannydvk11]

Re: can any one help me to understand

idle rpm should be at 650... Your tach is reading high. Even if the switch shows the correct position, you may have a defective one.

i will confirm tomorrow how much is it for sure

 

[bruceb58]

Re: can any one help me to understand

Do you know the gear ratio of your Alpha One drive? If it's the 2.0:1 Alpha and your GPS is showing nautical miles per hour then everything makes sense and you need a higher pitched prop.

I sure would hope not. Unless someone put on the wrong ratio drive.

 

[trendsetter240]

Re: can any one help me to understand

I sure would hope not. Unless someone put on the wrong ratio drive.

Nope. And the numbers don't make any sense with the information provided.

 

[mannydvk11]

Re: can any one help me to understand

Do you know the gear ratio of your Alpha One drive? If it's the 2.0:1 Alpha and your GPS is showing nautical miles per hour then everything makes sense and you need a higher pitched prop.

Where can I check my ratio

 

[steelespike]

Re: can any one help me to understand

The ratio is sometimes stamped on the outdrive. A 2.00 ratio usually appears on a 3.0 I don't think your boat is heavy enough to require that low of a ratio or for that matter if its available on a that size motor.

 

[mannydvk11]

Re: can any one help me to understand

The ratio is sometimes stamped on the outdrive. A 2.00 ratio usually appears on a 3.0 I don't think your boat is heavy enough to require that low of a ratio or for that matter if its available on a that size motor.

I will check on that today to

 

[bruceb58]

Re: can any one help me to understand

The ratio is sometimes stamped on the outdrive. A 2.00 ratio usually appears on a 3.0 I don't think your boat is heavy enough to require that low of a ratio or for that matter if its available on a that size motor.

That drive ratio is used for 4 cylinder engines. Extremely unlikely that is the issue.

 

[mannydvk11]

Re: can any one help me to understand

That drive ratio is used for 4 cylinder engines. Extremely unlikely that is the issue.

What will be a normal speed for my size boat my biges consern is I feel like the boat is to slow when am cruising at sl

 

[mannydvk11]

Re: can any one help me to understand

That drive ratio is used for 4 cylinder engines. Extremely unlikely that is the issue.

What will be a normal speed for my size boat my biges consern is I feel like the boat is to slow when am cruising at idle speed

 

[bruceb58]

Re: can any one help me to understand

What will be a normal speed for my size boat my biges consern is I feel like the boat is to slow when am cruising at idle speed

Why are you concerned with the speed of the boat at idle?

 

[mannydvk11]

Re: can any one help me to understand

Why are you concerned with the speed of the boat at idle?

Because I feel the boat like is dragging like if is force

 

[bruceb58]

Re: can any one help me to understand

So what is the history of this boat? How long have you owned it? Are you using the boat at sea level, salt water or fresh? Is the boat moored or on a trailer. Bottom paint?

Is the prop in perfect condition?

first thing though is to get a known good shop tach and see what your RPMs truly are. Then you can go from there.

 

[mannydvk11]

Re: can any one help me to understand

So what is the history of this boat? How long have you owned it? Are you using the boat at sea level, salt water or fresh? Is the boat moored or on a trailer. Bottom paint?

Is the prop in perfect condition?

first thing though is to get a known good shop tach and see what your RPMs truly are. Then you can go from there.

Well I own the boat for almost a year now my friend was the first owner and he was not using it so he sold it to me the paint is in perfect condition no bottom paint it's sitting on a float on trailer I use in salt water other then the upholstery everything Ells is god ill post some pics later the prop looks dissent but I will like to change it for another one with better performance

 

[bruceb58]

Re: can any one help me to understand

Can you post a picture of the prop?

How fast did the boat go when your friend had it?

 

[mannydvk11]

Re: can any one help me to understand

I will have pics of the prop tonight but this is some of my boat

 

[steelespike]

Re: can any one help me to understand

Why are you concerned with the speed of the boat at idle?

I think he may be confusing the term idle with cruising speed.
early on he said it seems to be dragging at 3000 also that wot produces 6,000 rpm.
If the tach is off that much 3000 is probably actually less than that so the boat would seem to be dragging.
We need to get the tach working or at least confirmed.