New kicker

Fishslayer · 02-24-2004, 07:40 PM

I'm looking to get a new kicker motor for my 23 ft fiberform. I have a t-8 yami that is a great motor but just not enough balls for a back up if out at westport or something. Any advise. I see the yami doesn't make a 15hp which would seem perfect? Thank in advance.

hrspowr · 02-24-2004, 08:26 PM

How do you like your Fiberform? I am looking at one right now. What year and style do you have? What do you like/dislike?

corrirod · 02-24-2004, 10:20 PM

That size of boat I'd get the biggest HP that you can. 15, 20, 25, whatever you can afford. I have a 20' Trophy with a 15hp on back and it isn't near enough to push that boat more than about 1-2 mph.

Maverick Maxcat · 02-25-2004, 05:03 AM

I ran a 24' Searay for years with a Yamaha 9.9 hi-thrust kicker, it worked great. The key is to get the prop below the boat's bottom so it's running in clean water. If it's too high the water will be turbulent behind the transom and you'll lose thrust forward, not to mention reverse. You don't have to go overboard on the horsepower. once your boat reaches it's displacement "hull speed" it takes major horsepower increases for small speed gains until you hit planing speed. You can find your "hull speed" easily with your main motor, probably 5-8 knots. If your T-8 will make this speed just keep it, even a 25 won't give you much more. If you need more motor I've got a T-25 Yamaha for sale in the ifish classifieds.
MM

Pitch Pocket · 02-25-2004, 07:58 AM

I can make 4 knots with my 9.9 yamaha high thrust on a 24' SeaSport. Kinda wish it would do 7-9 knots for tuna trolling. Would a 15hp give you that kind of speed?

SlabQuest · 02-25-2004, 08:12 AM

That's a good question, Pitch. I see that Yamaha makes a 25hp high-thrust that might do it. They also make a 50hp & 60hp for that matter. I think they phased out the 9.9 for the 8 (same thrust).

I would say that you would definately want to stay with the high-thrust design however. "Standard" OB's are designed to push little boats fast. H-T motors are designed to push big boats slow.

SlabQuest · 02-25-2004, 08:22 AM

Close approximation of hull (displacement) speed equals the square root of the boat's waterline length (in feet) times 1.34

25' waterline = 6.7 knots.

There was also some deal about when your bow wave reaches a certain spot, you're at hull speed, but I forget...

edsr · 02-25-2004, 08:26 AM

Would re-proping make a difference? Generally the factory sets up for a "typical boat" and this is not a "typical" applicaton. How big a prop can you get for that motor? That said you just might need more motor to get the job done. On my 23' dory the 8hp Honda will get about 6mph but it has been retro-fitted with a bigger prop, which could possibly be even bigger. You really don't want your trolling motor a full throttle all day.
edsr

SlabQuest · 02-25-2004, 08:40 AM

esdr,

H-T is done with a big low pitch prop (like a tug boat) and a lower gear ratio for a slower, stronger push.

Man, I'm hung-up on this hull speed deal this morning. I found this in my Power Squadron training book:

The vessel reaches maximum hull speed when the quarter wave reaches the aftermost point of the wetted surface. It has nothing to do with the bow wave.

Pitch Pocket · 02-25-2004, 09:06 AM

Yamaha still makes the T9.9 and the T8

Yamaha High Thrust Outboards

They have 2 props for the T9.9

Props for the T9.9

One has a speed rating for 3-7 knots (standard on the 8hp) and the other for 7-13 knots (standard for the 9.9).

They are selling a Dual Thrust plastic prop that is rated at 10-16 with 11 pitch and another rated at 12-18 knots with a 12-1/4 pitch. If a 7-13 gives me 4knots would a 12-18 give me 6?

Not sure of the cost, but there would be no decay in a plastic prop due to the dissimilar metal thing. They'd probably be a throwaway if you hit something though.

SlabQuest · 02-25-2004, 09:59 AM

Yes, but,

Where's the 9.9 on this page?

I think they're being phased out.

Pitch Pocket · 02-25-2004, 10:44 AM

Geez Slabquest, I don't know. :whazzup: They show the 9.9 on the introduction and standards/options page, but not on the specifications page you list. Heads will roll!

Did someone actually say they were phasing it out?

whalerpaul · 02-25-2004, 12:54 PM

which wave is the 'quarter wave'?

The vessel reaches maximum hull speed when the quarter wave reaches the aftermost point of the wetted surface. It has nothing to do with the bow wave.

thanks,
paul

Boatdog · 02-25-2004, 01:07 PM

Here's a definition of a quarter wave I found. I had the same question.

"As the bow wave increases in height, the distance between its crest and that of the wave following it, the quarter wave, increases until it approaches the waterline length of the boat itself."

Tyeebuster · 02-25-2004, 11:05 PM

I was told they Yamaha is going to discontinue the 9.9 High Thrust motor. However, I was also told that the 9.9 is still availible it Canada. I do know that there is a 9.9 High Thrust with power tilt that is currently availible in Canada. I have never seen this motor in the US. The only one that I have seen was on a @(' Coastal Craft at the Seattle Boats Afloat last month. Hope this helps.

SlabQuest · 02-25-2004, 11:15 PM

The rumor I heard was that they could offer the T8 w/ power tilt for about the same $$ as the T9.9 and that they had the T8 souped-up to deliver the same thrust as the T9.9.

But I also heard that the T8 actually has the powerhead of the 6.5 motor. The way I use my kicker, I feel better with the bigger powerhead of the T9.9.