1980 40hp mercury outboard

[dakotamike]

thanks for all the help so far......I am currently a 13p prop fully loaded I am running 4800 rpm at wot......research says I need to be between 5000 and 5500 rpms.....any advice on what pitch I should be running would be greatly appreciated

 

[Sea Rider]

What's the max wot rev while lightly (solo) boating ? For fully loaded escenario will need to go at least for 2 pitch in reduction, this is not rocke science, probably will over rev a bit at wot, just watch tach. Bear in mind that if boating alone or medium loaded as propped for fullyl loaded wot revs will shoot up, watch tach with both eyes....Is that a family oriented combo ?

Happy Boating

 

[fishin98]

A 15p would give you the RPM your looking for...probably more but you would not be pleased.....I would stick with the 13p as it gives you good all around performance...what kind of RPM do you get lightly loaded??? If your running MAX loaded all the time a 11p is the ticket. I ran 2cyl and 4 cyl mid range HP Mercs for many years and found the 13p to be the best comprise.

 

[dakotamike]

the oat is 1981 basstracker iiii fully loaded is two average guys and gear

 

[steelespike]

How is your hole shot and top gps speed with a light load?
At 40 hp your underpowered; boat is rated for 60 hp.The 40 was standard to keep the price down.
I figure your all up weight is about 1200 lbs with 2 adults aboard.Your wot rpm range is 4500 - 5500
Your barely within rpm range I think a 11" will give you a stronger performance with wot around
5200. May cost a title top end. An 11" Merc Spitfire 4 blade may retain top speed yet add
hole shot,and ability to stay on plane at reduced throttle.

 

[dakotamike]

I will probably never be light loaded or solo my gps speed is 26-27 mph at wot.....holeshot seems fairly good (doesn't seem to bog or anything) but I am new as I have only ever had a jon boat with electric motor lol thanks again

 

[steelespike]

I think you should wait until you have more experience with your boat and various conditions.
Interesting I did a rough estimate of your speed based on 4800 and 13" prop. came up with 26 mph.
I think that indicates the prop calculator works pretty good and your setup seems to be good.

 

[dakotamike]

I have had the boat on the Missouri river about a dozen times and numbers are fairly consistent +/- 1 or 2 mph in conditions from white caps to glass rpms constant