prop for merc 650

[jaymasta]

hey guys I have a 75 merc 650 on a 14ft f/g boat, 65hp, and from what I understand from the person I bought the boat off of it still has the original prop on the boat, right now I get about 30mph@5000rpm with 2 people in the boat and 6gals of gas, Iam not sure what the WOT is supposed to be I think it is from 5200-5600 but Iam not sure my local dealer wasn't sure either becuase the engine is so old, the only number on my prop is
48 61818A1 13P, Iam assuming its a 13" pitch prop but iam not sure what the other numbers mean if anything, the prop has some very small minor dings(1mm), and the paint is coming off on the back of the propeller and it looks as if there is some corosion going on the back of it as well, and Iam pretty convinced that a new one will make a differance, so any suggestions or recomendations would be helpfull, Iam thinking maybe a 12inch pitch or somthing to bring my rpms up a bit, if the engine can handle it, anyways thanks for your help in advance guys.
Jason

 

[jimmbo]

Re: prop for merc 650

4800 - 5300 is the rpm spec in the sales brouchure

 

[Crownie2]

Re: prop for merc 650

The new propellers might be a little different than your old one - it would be nice if you could try both 12" and a 13" - but I am with you - I am leaning toward the 12".

Also watch the diameter - it may be different.

Bob

 

[cougar1985]

Re: prop for merc 650

i had basically the same boat as you with a 1964 65 hp merc and i ran a 15p prop with very good results.the 64 was a large gear case model so maybe theres a diff.(2.1 ratio)

 

[jaymasta]

Re: prop for merc 650

i had basically the same boat as you with a 1964 65 hp merc and i ran a 15p prop with very good results.the 64 was a large gear case model so maybe theres a diff.(2.1 ratio)

Iam not sure what my gearcase is but wound't a 15p be way to much for mine giving that mine struggles a bit with 2 ppl in the boat and towing a tube, how does the diameter of it effect the pitch, would going to a smaller diamete but more pitch make a diferance? I don't know what diameter my prop is but it looks to be between 9-11" or so although I could be off a few inches its hard to tell, what speeds were you hitting with your 15p prop?

 

[kenmyfam]

Re: prop for merc 650

Dropping the pitch will increase the RPM about 200 rpm per inch of drop. 5300 rpm is the max WOT on that engine from my recollections. Same diameter and 1 inch less pitch should bring you up nearer the max RPM for your motor.

 

[cougar1985]

Re: prop for merc 650

yes by looking at 2 different props that i have ,1 from my old 65 and 1 from a newer 60 mariner and a 70,s merc i would say that 15p would be too much for your application.my old merc prop is much larger than your prop.im with kenmyfam on this one and would say 12p for you.

 

[cougar1985]

Re: prop for merc 650

seen your pics of your boat ,13 p prop should be the best all around i would think.your prop on there looks the same as mine,with the 15 p i would guess i was going low to mid 30,s.with newer props you will get better performance. on the rig i got now i bought the mich wheel vortex prop with the xhs hub system.i have 2 props now one for heavy loads and 1 for regular use. the beauty of the vortex is that you only need to buy 1 hub for all the props so you save on cost.

 

[jaymasta]

Re: prop for merc 650

Interesting,
well I would like to get a 12P for when Iam towing people, I don't really care to much about top speed as long as Iam around 30mph. I know the 12p will definatly make a diference as well as Iam going to put on the smart tabs, what kind or what are some things I should look for in a new prop or any recomendations, Iam going to stick with a aluminum just becuase of cost... but as far as other features or quality any tips or adivce, or certain prop recomendations?

 

[jaymasta]

Re: prop for merc 650

Interesting,
well I would like to get a 12P for when Iam towing people, I don't really care to much about top speed as long as Iam around 30mph. I know the 12p will definatly make a diference as well as Iam going to put on the smart tabs, what kind or what are some things I should look for in a new prop or any recomendations, Iam going to stick with a aluminum just becuase of cost... but as far as other features or quality any tips or adivce, or certain prop recomendations?

 

[Crownie2]

Re: prop for merc 650

Well there is the Michigan Vortex.

You could buy one hub and then the two different pitched props could be interchanged on the same hub.

Merc may have the same setup with their Flow Torque II hub system.

Bob

 

[hibbert6]

Re: prop for merc 650

I have the exact same engine and saw this incredible prop at West Marine right after I'd ordered mine. (Rats.) It is a composite prop that allows you to adjust the pitch with a twist of the hub, up or down one number. So you could buy the 13 pitch, but be able to run it as a 12,13 or 14 pitch. Cost was $150 complete with hub.

I bought a Piranah composite prop and am very happy with it, but I'd love to have the adjustability!

I have the "wing" fins bolted onto my engine (can't remember what they're called) and my boat planes well. This combo has been great for tubing.

You don't pull tubers at 30mph do you?!!?

Dave