prop pitch problems on a frankenstien

[droptheline]

I got an 89 3.0 with an alpha 1 outdrive geared for a 470, its got a 17" pitch prop and makes that noise (past 3/4 throttle) like when you try take off in your car in 3rd gear, (clinck clinck clinck) unfortunatley i dont have an tachometer, but sounds like the motor has at least 1,000 rpm's left in it a wot, any ideas on what prop/pitch might help me out? thanks a million

 

[ziggy]

Re: prop pitch problems on a frankenstien

your not gonna be able to do any proper prop testing for best results because you don't have a tach. you will have no facts to base any opinion on.. + you may have the improper gear ratio in the drive since it's not the 3.0 drive.. i don't know the difference in ratios or if there is one. but you need to find out to see if it can even be propped proper. if gear ratio is too far off, you'll never get it right with prop pitch changes..

i don't understand your description of the prop making noise... unless perhaps it's piercing the surface or cavitateing real bad maybe... if it's cavitating that bad, your prop will look like it's being ate up. which if it's cavitation, it is being ate up..

 

[droptheline]

Re: prop pitch problems on a frankenstien

the prop doesn't make noise the engine does, ever hit fifth gear thinking it was third, clink clink clink goes the engine, thats what im getting past 3/4 throttle cause its geared slightly off , i have a 17 pitch so im thinking 15 pitch, i find it hard to believe that no one has ever had a 1 to 1.89 (470) gear ratio outdrive on a 3.0 as they are very close and was hoping someone knew exactly what pitch i needed before i waste a hundred bucks and be 1 pitch off you know. thanks for all replies.

 

[ziggy]

Re: prop pitch problems on a frankenstien

i find it hard to believe that no one has ever had a 1 to 1.89 (470) gear ratio outdrive on a 3.0 as they are very close

yes, they are. but i had to go find a somewhere to find that out. http://www.seilermarine.com/info/mercruiser-drive-ratio-chart.htm
so the gear ratio perhaps can be overcome by prop pitch.. still. in selecting a proper prop. your basically wanting to achieve the top of your wot rpm spec. and since every boat is different. the prop selection will be different, based on wot rpms. which we can't know w/o a tach reading.

the prop doesn't make noise the engine does, ever hit fifth gear thinking it was third, clink clink clink goes the engine, thats what im getting past 3/4 throttle cause its geared slightly off , i have a 17 pitch so im thinking 15 pitch,

you could be overpropped. but how would you know w/o a tach reading to know what your wot rpm really is. ya need a tach. i think..

i know thats not what you want to hear. but it's the best info i can offer.. hopefully someone else will let you in on what they think too..

 

[hwsiii]

Re: prop pitch problems on a frankenstien

Drop, you gave me the gear ratio, now I need to know the horsepower and if the motor has good compression and EXACTLY what manufacturer and model of prop you are running. With this information I can at least check to see if you are anywhere near decent guidelines. BUT you need a TACH, You ever heard the old axiom about a penny and a dollar, WELL saving the money on a tach could cost you the motor in the boat, especially if it is clanking. If you REALLY just can't afford a tach let me know and we will try to figure something out, I know times are hard right now for a lot of people and it is not their fault.

H

 

[droptheline]

Re: prop pitch problems on a frankenstien

Its a 3.0 130 hp, good clean running motor, steady oil pressure, i guess ill get a tach and check back with what number im running at wot, i have a 15" dia 17 pitch aluminum prop, dont know the make, quicksilver probably? will get a tach and post asap, thanks for the replies!

 

[droptheline]

Re: prop pitch problems on a frankenstien

Its a 3.0 130 hp, good clean running motor, steady oil pressure, i guess ill get a tach and check back with what number im running at wot, i have a 15" dia 17 pitch aluminum prop, dont know the make, quicksilver probably? will get a tach and post asap, thanks for the replies!

 

[180shabah]

Re: prop pitch problems on a frankenstien

I think your prop pitch is secondary, your just not going to create the same load as a car in 5th at 15mph, on a boat, the prop will slip (to a certain point). Think power braking with an automatic in a car.

When was the last time a full tune up was done? Do you have a water seperating fuel filter?

 

[droptheline]

Re: prop pitch problems on a frankenstien

Last year for the tune up, and yes got a water seperator, you think it could be as simple as that, the boat runs great other than the jingling sound past 3/4 throttle, its the exact sound you get when you run a motor in to high a gear. gonna get a tach and go from there. will post with my rpm's. since the outdrive is geared for 170 hp and im only running 135 im guessing over reving is not my problem but we'll see.