is my boat over propped??

[dhonda]

I have a 1957 crestliner viking 14' with a gale 40hp on it and i was wondering if my boat is over propped because when u drive the boat with 2 people and both fuel tanks almost empty it goes 30mph and accelerates pretty quick and gets up on plane nice and quick but once u fill both fuel tanks up the boat takes quit a while and strugles to get up on plane then once it does itl only go 28mph and takes along time to get up to that. Now add another person in the boat ontop of the tanks being full and the boat is like 26mph and barly gets on plane. I have a 10 3/8 x 13 1/2. pitch prop on it and i have a spare 10 3/8 x 12 1/2. pitch should i try that prop?

 

[phebus1]

Re: is my boat over propped??

Based on symptoms alone, yes you are over propped. Proper prop selection would be based on WOT rpm.
Does the boat have a tach?

 

[Silvertip]

Re: is my boat over propped??

You will never know until you know what the maximum rpm is with what you consider an average load. The only way you know that is to install a tachometer. All engine manufacturers specify a wide open throttle rpm range which generally falls in the 5000 - 5500 or 5500 - 6000 range with some even higher. If, with an average load, the engine cannot reach it's recommended wide open throttle rpm the engine is considered "over propped" or it simply is not making full power because of age, wear, tuning, etc.

 

[dhonda]

Re: is my boat over propped??

Based on symptoms alone, yes you are over propped. Proper prop selection would be based on WOT rpm.
Does the boat have a tach?

The boat does have a tach but i dont beleive it is accurete. The motor should be between 4000-5000rpms so 4500rpms is probly best but my tach will show it going up to 6000rpms then itl go down to 5000rpms sometimes it varies so i dnt rlly know what rpms the motor runs. From what ive read my motor isnt designed to have a tach, one man told me that i have to have a stator and a rectifier or rectifier/regulator to make todays tachs work. i was told my motor dosnt have any of that. is there any way of riging up a tach temporary to the spark plugs possibly?

 

[etracer68]

Re: is my boat over propped??

There are tachs, that go to a spark plug, called tiny tachs.

 

[steelespike]

Re: is my boat over propped??

When it was built it was intended for boats like yours.The viking weights range from 235-340 the max hp was 60.
In 61? these props were available.11 1/2",12 1/2",13 1/4",and 14". Your boat total weight with 3 adults 450,
2 tanks of gas and 2 tanks 116,motor about 130,boat about 300 = 996lbs.Asking a lot of 40 hp.
I'm guessing you have a 13.25 prop Your gear ratio is 1.75,guessing 8% slip and we know your 30 mph speed
the motor would be turning about 4500 rpm.right in the middle of its range.
Keeping in mind we need to confirm your present prop size If you go to a 12 1/2" prop assuming it adds about 300 rpm your light load speed would be just under 30 would be easier to get a load on plane and may run faster.Before a prop change try some weight balancing.
probably your tanks are in the stern if you move them up under the front deck that should help
It probably has a rear seat if the additional person sits there you could try putting them in front.
When your loaded adjust the trim in one notch. Let us know if anything helps.

 

[dhonda]

Re: is my boat over propped??

steelespike thanks! when there are 2 people in the boat we both sit in front and if my dad goes to the back of the boat to adjust the air screws or w/e he may be doing the boat wont evan get on plane if the tanks r full. That is with the motor pin 3rd. when the weather gets nicer i will take the boat out and try it with the motor 2nd pin in and see if that helps if its not enough ill try the 12.5" prop.

 

[steelespike]

Re: is my boat over propped??

Don't forget we are assuming a 13 1/4" prop.You need to confirm that.
Maybe you could put the standby tank up under the bow or behind the front seat.Its almost like a 100lb change when you remove 50lbs from the back and add it to the front.
Does your boat have a steering wheel ,windshield ,floor etc?By the way I have a 57 Bucaneer 18ft utility with a 65 Merc 500 tiller.
It was the neighbors boat ,I rode in it when it was new.Its in wonderful unrestored condition.
Have you been to the retro Crestliner site?

 

[dhonda]

Re: is my boat over propped??

Don't forget we are assuming a 13 1/4" prop.You need to confirm that.
Maybe you could put the standby tank up under the bow or behind the front seat.Its almost like a 100lb change when you remove 50lbs from the back and add it to the front.
Does your boat have a steering wheel ,windshield ,floor etc?By the way I have a 57 Bucaneer 18ft utility with a 65 Merc 500 tiller.
It was the neighbors boat ,I rode in it when it was new.Its in wonderful unrestored condition.
Have you been to the retro Crestliner site?

I checked my prop and it is infact a 13 1/4" also my boat does have a steering wheel and a windshield in the front, my neighbor gave me the boat and he is a wood worker so he covered the top and interior with wood so the boat looks like a chris craft when its in the water. 57 Bucaneer 18ft are very nice boats too! i have not been to the crestliner site but i will check it out. I will also try to move the extra fuel tank to the front of the boat or at leats behind the front seat and see if that helps