8 hp tp 9.9 hp differences

[basscat]

I sometimes fish in my friend's aluminum boat (14' Lowes, probably 10 years old or more). We fish with a total weight of fishing gear, loaded down ice cooler with 3 humans for a total number of 840 lbs. plus or minus 25 lbs.

He's running a Yamaha 8 hp 4-stroker now and offered a deal on a older (10 year) Honda 9.9 motor. Does anyone know if the near 2 hp difference will make the boat go faster? And if so, by approx. how much more?

Reason: in some of the lakes it's nicer on a slow day to try another spot that could be further away but don't want to spend half the day getting there. You all know time is precious and limited and saving the non-fishing time of no lines in the water is just that.

[fishinone]

That's an almost 25% increase in power. It could be considerable, 8 mph could become 10 mph. Actual performance would depend on prop pitch and diameter, planing surface and motor tuning. If the boat doesn't come up on plane with the current motor, your gain could be considerably more if you get it to plane.

I have a friend who has a 14' aluminum boat with Honda 9.9. It does pretty well with 3 guys. It comes up on plane but not much more, maybe 12 or 13 mph.

I think your buddies boat would do much better with the added power.

[DockRat]

That's an almost 25% increase in power. It could be considerable, 8 mph could become 10 mph. Actual performance would depend on prop pitch and diameter, planing surface and motor tuning. If the boat doesn't come up on plane with the current motor, your gain could be considerably more if you get it to plane.


:Applause: That is a great response. It is possible that a different prop could fix the problem.
A good propeller shop could help but you would need to know the prop size inches and pitch.
Wilmington Propeller is good. They do small up to big ship props.

We fish with a total weight of fishing gear, loaded down ice cooler with
3 humans for a total number of 840 lbs.

Does that weight include the motor ? Gas ? How many gallons ? 6.175 lb/US gal.
How much does the motor weigh ?
DR

http://i12.photobucket.com/albums/a209/jill_wootton/August%201/PaulAndPropellor.jpg

[Kevman]

DR brings up a good point. Without knowing what RPM your 8HP maxes out at right now with your somewhat heavy load, you don't know if it's hitting its proper torque/HP curve. They make add-on tachometers for small outboards such as this one: http://www.tinytach.com/tinytach/gasoline.php

Not affiliated, blah, blah.

If you know your 8HP's recommended redline range (which you can easily look up online if you know the year and model #) you can easily find out if your prop is giving you all the motor has got.

Another consideration is the condition of the older Honda 9.9 you are being offered. If your 8HP is essentially brand new with perfect compression, and you change to a 15-year-old 9.9 with weaker compression, weaker spark, etc., you may end up with the same HP you started with. Keep in mind that when most people say the used outboard they are selling is 10 years old they really mean 15-20 years old. The only way to be sure is to look up the model # and serial # online. Plenty of places have charts that will tell you the true age.

Another thing to keep in mind is that with engine technology getting better, outboards are using smaller blocks and less displacement to generate the same amount of horsepower. That means an old motor can have more torque than a same-HP-rated new motor. Sometimes torque is almost more important than horsepower. For example, I guarantee that a properly-tuned flathead 9.9 Johnnyrude will beat the pants off a 4-stroke 9.8 Tohatsu/Nissan in HP, torque, and ultimately boat speed due to the much larger displacement and much higher torque. The 'Rude is about 15-20 pounds lighter as well. Granted that's comparing a 2-stroke to a 4-stroke, but you still get the idea.

So to summarize, there are lots of factors at work here and you must look into all of them if you want to make the right motor choice.

Good luck and good fishin'!

Kev

[DockRat]

Other methods to increase speed.
1) Switch from beer to hard liquor.
2) Use dry ice instead of cubes.
3) Get lighter fishing partners say 125 lbers.
200 lbs + taken off with these 3 steps = increased speed and less fuel consumption.

http://i908.photobucket.com/albums/ac286/vitormiro/Meninas%20do%20fly/sexy_fly_fishing_2.jpg
DR :LOL:

[basscat]

Thanks guys!! Points well taken....great advice...

Didn't take the motor's weight nor the 5 gals. of gas.....nor the RPM factor, etc...I'll be seeing him later this weekend to discuss.

But I'll have to use DR's post slightly better, I'm going to kick out the skipper and other fishing buddy and bring the trout babe instead...done and problem solved...forget the other motor, not needed now, lol....boy, is she a looker or what??!! Could be my new screensaver when the wife's not around....