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Yamaha 8 High thrust question

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dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 02/07/2004 : 09:41:52

When evaluating alternator output, keep in mind that the advertised amperage is attained at either wide open throttle or some other higher rpm, which on a displacement boats like ours, is never attained due to hull speed limitations.

Edited by - dlucier on 02/07/2004 09:42:56

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/07/2004 : 11:00:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by dlucier
 When evaluating alternator output, keep in mind that the advertised amperage is attained at either wide open throttle or some other higher rpm, which on a displacement boats like ours, is never attained due to hull speed limitations.

<hr height="1" noshade id="quote"></blockquote id="quote">
The new Honda is rated at 12 amps at 3000 RPM (around cruising speed) and 6 amps at 1000 RPM. Yamaha is rated at 6 amps max (no RPMs stated).

Come to think of it, this might be why Arlyn found the gas mileage to be a little worse on his new Honda.

Edited by - Dave Bristle on 02/07/2004 11:03:03

Scott L
1st Mate

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52 Posts

Response Posted - 02/07/2004 : 11:46:02

Gary - Anyone,
When you had the older Yamaha 9.9, do you remember ABOUT how many hours you could cruise on 5 gallons of gas? Ball park? 4-6, 6-8, 8-10, 24-48???

Edited by - on

dlucier
Master Marine Consultant

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Virgin Islands (United Kingdom)
7583 Posts

Response Posted - 02/07/2004 : 11:55:14

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave Bristle
 The new Honda is rated at 12 amps at 3000 RPM (around cruising speed) and 6 amps at 1000 RPM. Yamaha is rated at 6 amps max (no RPMs stated)...<hr height="1" noshade id="quote"></blockquote id="quote">

True, no RPMs are stated for the amp output on the Yamaha, but according to the [url="http://www.yamaha-motor.com/products/subcatspecs.asp?lid=5&lc=otb&cid=19&scid=4&but=16&year=2004&cat=Four+Stroke+Series&scat=High+Thrust"]Yamaha[/url] website, the alternator output is 6 amps at wide open throttle (WOT) and the RPM range is 5,000 to 6,000.

Edited by - on

RichardG
Admiral

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USA
990 Posts

Response Posted - 02/07/2004 : 13:33:51

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Do our wants have a high cost? Perhaps more than we would care to honestly admit<hr height="1" noshade id="quote"></blockquote id="quote">

VERY well put.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 02/07/2004 : 14:09:39

I agree, and have thought that the increased alternator output would burn calories.

I went from 2.25 hours per gallon on the Honda 8 Classic at a cruising speed of 5.5 knots to 1.6 hours per gallon on the 2001 HT 8 hp.

For those who measure in how much per hour...the figures are, .44 gal per hour on the 8 Classic to .62 That means I took a near 50% hit in fuel economy.

However, the alternator should not burn calories if its not under a load, and I know that there are times when the batteries were topped up and the fuel consumption didn't change a lot...from the 1.6 hrs per gal.

I think the big difference is that the Clasic 8 was a true 8 hp displacment... and fuel consumpiton is not a real big issue for other than the cruiser who may be covering long distances and that doesn't normally come into play on a coastal cruiser which needs to watch a 24 hr weather window.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/07/2004 : 14:41:06

MPG and HPG don't mean much to me--I burn 5-15 gallons a season. But crossing Long Island Sound is not quite the same as crossing Lake Huron!

Edited by - on

lcharlot
Master Marine Consultant

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Antigua and Barbuda
1301 Posts

Response Posted - 02/08/2004 : 02:18:22

I stopped at the local outboard shop today to compare the Honda and Yamaha offerings. Here are the key features and differences:

1. The Honda and Yamaha both have large diameter propellers, but the Yamaha has 30% lower gearing, which should give the prop more "bite" and less cavitation than the Honda, at the slow speeds of a sailboat.

2. New for 2004, the Yamaha T8 has a recoil starter in addition to the electric starter. HOWEVER, this is NOT the case for the Yamaha 9.9; it still comes with electric start only. The Honda 8 has both electric and recoil starters.

3. The Yamaha 8 has an exceptionally long tiller handle, looks to be 6 to 8 inches longer than other 8 hp 4-stroke outboards from Honda, Nissan, Tohatsu, and Mercury.

4. The Yamaha 8 has the gearshift on the tiller, another feature I have not seen on comparable motors.

5. The Yamaha 6hp and 8hp use the same engine, with the difference being the 6 has a more restrictive carburetor. The Yamaha 9.9 and 15 are the same engine, again with the 9.9 having a carburetor restriction. The service manager at the shop told me that this is why the 9.9 didn't get a recoil starter, whereas the 8 can use the same recoil starter assembly as the 6.

6. The Yamaha 8 is available only with a 6 amp alternator, the 9.9 has a 10 amp. I suspect that the smaller amp output was justified by the motor having a recoil starter; even if the battery is too low to crank the starter, you can just pull start it. As has been pointed out by Dave Bristle and others, the problem with the small 5 and 6 amp alternators is that you can only get that at max rpm, a condition that we almost never use on Catalina 25's since they reach hull speed at about 1/2 throttle. At half throttle, the alternator is probably delivering no more than 2 or 3 amps to the battery (practically useless).

7. Price: The Honda 8 and Yamaha 8 are priced almost identically, at least at this shop: $2317 for the Yamaha, and $2295 for the Honda.

8. Weight: Both motors weigh in at slightly over 100 pounds (102 for the Yamaha and 110 for the Honda if I recall correctly).

9. Powerhead cover: The Yamaha 8 engine cover doesn't seem to be significantly larger than the cover on the old Honda 7.5 I have on the boat now, so I expect that clearance for tilting the motor is probably okay.

Conclusion: Now that the Yamaha is finally available with a standard recoil starter to back up the electric starter, I believe it has a clear advantage over the Honda as an auxiliary for Catalina 25's or 250's. The extra-long tiller with handle mount gearshift, and the 3:1 gearing make it ideal. The only disappointment is the lack of a real alternator, 12 or 13 amps. The Honda and Yamaha weigh about the same, are priced within a few dollars of each other, both are available in a 25" shaft, and both get about the same fuel economy.
I will probably pick one up as soon as I sell my old boat, at which point the new boat will be moving to dry storage at Folsom Lake. Swapping the motors will be a lot easier and safer with the boat on the hard than trying to do it with the boat in the water where it is now.

Edited by - on

Arlyn Stewart
Master Marine Consultant

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USA
2980 Posts

Response Posted - 02/08/2004 : 08:07:36

Larry,

Great comparison. Question. Was the Yamaha six available in XLS?

Edited by - on

Doug
Captain

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USA
457 Posts

Response Posted - 02/08/2004 : 10:41:38

The Yamaha T8 comes in a 25"XLS shaft.
The story I got when shopping around was that the Yamaha 9.9 is essentially the same engine they've been making for years. The Honda is also an old design that's been updated and modifed over the years. The Yamaha T8 is a new motor built from scratch.
A couple of other little things Larry forgot to mention:

Fresh water flush on the outside of the engine.

Can change the oil without pulling the motor off.

Optional power tilt

Yamaha financing promotion through February: 0% interest for a year.

Motor just looks better than the Honda. To me the Honda just looks so darn big.

Edited by - on

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