Merc 470 Prop Choice/Query

[pcmpete]

Hi there, I am looking for a prop for my setup, boat came with no prop, so I need your help.

My info:

Iboats Boat and Motor Info

1. Year, make and model of boat
1978, Reinell T180 (Nada: http://www.nadaguides.com/default.as...R&d=1600148440)

2. Length, width and base weight of boat, look for boat decal on back of boat
17ft, 7'3", 2000lbs

2a.What is the maximum recommended HP for your boat
Max recommed is 120hp according to NAPA, but has a Merc 470 170hp

3. Number of people and gallons of gas normally on boat
Mainly just two adults, 34gal tank

4. What do you use the boat for
General cruising, rarely towing

5. Is it a Deep Vee and if so how many degrees of deadrise
No. degrees unknown

6. Year, make. manufacturer and model of motor
1978, Mercruiser 470

7. HP and gear ratio of motor IMPORTANT
170hp, 1.84 ratio

8. Manufacturer?s recommended Wide Open Throttle (WOT) range
3800-4200

9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches, use a board under the keel and stiking out to the anti ventilation plate for a referene
unknown


10. Is it a bass boat or does it have a pad bottom
NO

11. Does it have a hydrafoil, dolefin or trim tabs
No

12. Make, model, diameter, pitch and whether SS or aluminum prop
N/A

13. WOT RPM and speed from your current prop
unknown

14. Are you at sea level or a higher elevation, give us the elevation in feet
2000ft

15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
fresh rebuild

16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
N/A

17. Does the prop show any damage that you can see
N/A

18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations
N/A

19. If you are trying to attain a better cruising speed and fuel savings or trying to attain a faster speed I will want you to take your boat and run it with 1 or 2 people and give me the RPM and speed readings starting at 3,000 RPM in 500 RPM increments all the way to WOT.
Looking for average hole shot with a good top-end.


Thank you for your time.

I look forward to your reply.

Pete

 

[thompy]

Re: Merc 470 Prop Choice/Query

i think you would be pretty safe with a 19, but it would probally also pull a 21

 

[TBTOsterman]

Re: Merc 470 Prop Choice/Query

My 19p alum over reved my 470 but had a great hole shot. I ran a 21p alum when I had a light load but the hole shot was no good. I usually ran the 19p and watched the rpms. It was the best for all around. My 1981 18' Webbcraft weighed about 2800lbs and topped out at about 42mph.

I hope this gives you an idea.

 

[pcmpete]

Re: Merc 470 Prop Choice/Query

My 19p alum over reved my 470 but had a great hole shot. I ran a 21p alum when I had a light load but the hole shot was no good. I usually ran the 19p and watched the rpms. It was the best for all around. My 1981 18' Webbcraft weighed about 2800lbs and topped out at about 42mph.

I hope this gives you an idea.

I am leaning towards a 21" maybe even a 23".
The boat is only 2000lbs dry and 16ft in length, so I think the 470's 170hp should handle the extra bit of pitch.