can any one help me to understand

[Tail_Gunner]

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

well guys i took the boat out today i am really happy with the performance at idle i know-this i was not able to hit pass 38 MPH probably am doing something wrong o how to get to plain o how to get the boat to get more speed i also was testing with the shop meter and the reading i was getting was 480 X 10 = 4800 WOT @ 38 MPH gps i do feel my engine is allot more smooth i don't feel the drag on idle and it have good power do you guys think i can improve the MPH can i do better o that's it BTW my tachometer on the boat was @ WOT 6800 RPMs i am looking for a replacement any subjection's thanks

Nothing has changed you went from a 17 to 21 same speed as to rpm who really know's. That hull is not going to drag that much..weigh the boat at a truck scale...get a second reading on a different gps..have somone look at the drive coupler...Something is totally amiss.

 

[mannydvk11]

Re: can any one help me to understand

well guys i took the boat out today i am really happy with the performance at idle i know-this i was not able to hit pass 38 MPH probably am doing something wrong o how to get to plain o how to get the boat to get more speed i also was testing with the shop meter and the reading i was getting was 480 X 10 = 4800 WOT @ 38 MPH gps i do feel my engine is allot more smooth i don't feel the drag on idle and it have good power do you guys think i can improve the MPH can i do better o that's it BTW my tachometer on the boat was @ WOT 6800 RPMs i am looking for a replacement any subjection's thanks

Nothing has changed you went from a 17 to 21 same speed as to rpm who really know's. That hull is not going to drag that much..weigh the boat at a truck scale...get a second reading on a different gps..have somone look at the drive coupler...Something is totally amiss.

Can I be doing something wrong when I put the boat at wot , what I do hit the throle to ill get to wot and ones is on plaine ill let it get speed

Something Ells I have a teleflex tachometer do u guys recommend any brand model in particular

 

[jestor68]

Re: can any one help me to understand

My previous post was based upon the assumed gear ratio, which we now know was incorrect.

Based upon the actual gear ratio, the perfect aluminum prop for your boat is the Solas Amita 15-3/10 x 21 pitch. The larger diameter is what is needed for your gear ratio and weight. The increase of about an inch of diameter will pull your rpm down about 200 and provide the thrust needed to efficiently move your boat. That prop will get you to about 40 mph at 4600 rpm, as well as better out of the hole acceleration and cruise performance.

Going one better in SS would be one of the Solas Rubex L3 props of 15 X 21 or 15-3/4 X 21. Since these props would provide even better performance compared to the Amita; you would need to decide whether the triple price tag is worth it.

My recommendation for instruments is Faria.

 

[Tail_Gunner]

Re: can any one help me to understand

Can I be doing something wrong when I put the boat at wot , what I do hit the throle to ill get to wot and ones is on plaine ill let it get speed

Something Ells I have a teleflex tachometer do u guys recommend any brand model in particular

You do trim the outdrive out as you go to wot...to the point of slipping then trim back for a solid hook up.

 

[bruceb58]

Re: can any one help me to understand

You do trim the outdrive out as you go to wot...to the point of slipping then trim back for a solid hook up.

You are better off watching the speed than doing it that way but it depends on the boat.

I have a fuel flow meter on my boat. If I am going to be going the same speed over a long distance, I trim to max MPG as the flow meter is incorporated into the GPS.

 

[Tail_Gunner]

Re: can any one help me to understand

You are better off watching the speed than doing it that way but it depends on the boat.

I have a fuel flow meter on my boat. If I am going to be going the same speed over a long distance, I trim to max MPG as the flow meter is incorporated into the GPS.

Same here something is drastically wrong here. and very basic. Dunno why this is going on so long. it is impossible to acheive the same speed from a 17-21 unless the hull..drive are wacked....for the lack of a better word.

1. Not trimming the drive
2. Water laden hull
3. Coupler slipping
4. Timing issue
5. Hub's slipping

 

[bruceb58]

Re: can any one help me to understand

Only thing that he could do is to put the smaller prop on and compare the speeds/RPM with the shop tach he has now. If he had spinning couplers or hubs, he wouldn't be going 38MPH without smoke or other issues.

 

[trendsetter240]

Re: can any one help me to understand

Same here something is drastically wrong here. and very basic. Dunno why this is going on so long. it is impossible to acheive the same speed from a 17-21 unless the hull..drive are wacked....for the lack of a better word.

1. Not trimming the drive
2. Water laden hull
3. Coupler slipping
4. Timing issue
5. Hub's slipping

Maybe 260hp just isn't enough to push that boat faster than 38-39 mph no matter what prop is on it? If the numbers are accurate now then he's no longer hitting the rev limiter though the prop is slipping 28%.

 

[mannydvk11]

Re: can any one help me to understand

You do trim the outdrive out as you go to wot...to the point of slipping then trim back for a solid hook up.

put the out drive down before i start WOT and i live it like that

 

[Tail_Gunner]

Re: can any one help me to understand

Well now were getting somewhere... the root cause of your problem's. but congratulation's you have just found a new boat. The next time you go out leave it in the down postion...once you get on plane start trimming the outdrive away form the boat add gas trim more add gas trim more...Soon you will get the hang of it..then when at wot trim it out until your tachs jumps and your speed goes down then back it in until your speed and rpm are at there best...take notes of what you are doing...you should get another 5-10 mph...Think of it as a self inflected wack... And welcome to boating..just stay away from the launch area's laughing at other people's mistake's...You know youve gone a bit to deep if you do that..:facepalm:


http://www.boattest.com/Resources/view_news.aspx?NewsID=4054

 

[mannydvk11]

Re: can any one help me to understand

Only thing that he could do is to put the smaller prop on and compare the speeds/RPM with the shop tach he has now. If he had spinning couplers or hubs, he wouldn't be going 38MPH without smoke or other issues.

i order a new tach to see if it makes a differences i will try to see if i take it out any time this week

 

[mannydvk11]

Re: can any one help me to understand

Maybe 260hp just isn't enough to push that boat faster than 38-39 mph no matter what prop is on it? If the numbers are accurate now then he's no longer hitting the rev limiter though the prop is slipping 28%.

i never hit the rev limiter the tach was giving me the wrong info and i din't know until i starter testing because my concern it was to hi RPM then we found all the different problems

 

[mannydvk11]

Re: can any one help me to understand

Well now where getting somewhere... the root cause of your problem's. but congratulation's you have just found a new boat. The next time you go out leave it in the down postion...once you get on plane start trimming the outdrive away form the boat add gas trim more add gas trim more...Soon you will get the hang of it..then when at wot trim it out until your tachs jumps and your speed goes down then back it in until your speed and rpm are at there best...take notes of what you are doing...you should get another 5-10 mph...Think of it as a self inflected wack... And welcome to boating..just stay away from the launch area's laughing at other people's mistake's...You know youve gone a bit to deep if you do that..:facepalm:


How to Trim Your Outboard or Sterndrive | BoatTEST.com

i never done that lol that is something new for my next test :laugh:

 

[Tail_Gunner]

Re: can any one help me to understand

i never hit the rev limiter the tach was giving me the wrong info and i din't know until i starter testing because my concern it was to hi RPM then we found all the different problems

Read that link...the boat is fine you will be amazed when you learn to trim out that drive...hope for 50 mph..

 

[trendsetter240]

Re: can any one help me to understand

i never done that lol that is something new for my next test :laugh:

It's going to make a big difference. Get a new tach installed before you test so you can easily monitor the RPMs.

Good Luck.

 

[mannydvk11]

Re: can any one help me to understand

really good link i will try all that and see how it go

 

[mannydvk11]

Re: can any one help me to understand

well guys i took the boat out today for a test i install a new tachometer and compare with the shop tachometer @4900 i get 39.5 MPH the is going on a flat water WOT and trimming up and down to get the most out of it i try at least 5 times and got the same 39.5 MPH and i was using the boat gps+navionics app on the iPhone

 

[bruceb58]

Re: can any one help me to understand

@4900 i get 39.5 MPH

repeat after me..."4900 RPM is too high. I should never go over 4400 RPM"

 

[mannydvk11]

Re: can any one help me to understand

i know bruceb58 but i have to test in order to see where am suppose to be now i will need the magic number for the prop should i go with a 15 X 23 p or a diffident number

 

[trendsetter240]

Re: can any one help me to understand

i know bruceb58 but i have to test in order to see where am suppose to be now i will need the magic number for the prop should i go with a 15 X 23 p or a diffident number

Hey mannydvk11, no 23p is not the right prop for your boat. Your current prop is slipping and not performing as it should. You should be reaching 48 mph with a 21p prop.

You should look for a prop that will grip better and provide more thrust. The 14x 21p solas amita 4 blade is still the prop I would recommend for you.

Another poster suggested the Solas Amita 15-3/10 x 21 which would also be a good choice.