Yamaha f9.9 fuel consumption

seanfoster

seanfoster

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I found a thread relating to these outboards, but couldn't find the info I was after.

I have a Yamaha F9.9 (AE) outboard, (1990 model, white, electric start) which came with my present boat. I haven't done anything with it yet and I'm about to give it a complete overhaul.

Does anyone who has a similar engine know what fuel consumption I am likely to get from it?
It will be sitting on the back of a Dufour 1800 (25ft 1800kg disp yacht) so I was wondering litres per hour at say half, 3/4 and full revs?

Also from what I've found out it will charge a battery at 6 amps at full revs, would anyone agree with this?

Also any general tips or experiences would help!
 
No idea of the fuel consumption except that it should be a lot less than a 2 stroke! I would have thought that for a yacht the high thrust version might have been a better choice though.

The rated electrical output is 6amps but that will be its maximum. You may get that initially into a well discharged battery but it will almost certainly fall as the battery charges. I think it is a regulated output although I don't know for sure without looking into it more deeply.
 
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seanfoster said:
Unfortunately I didn't have a choice as it came with the boat, apparently it has a high thrust prop?!
Click to expand...

Thats good. It means that it should have a lower pitch than the standard prop which is more suitable for fast moving craft. It may also have a larger diameter and or area.
 
email Yamaha Uk, they are very helpful. They will put you intouch with your nearest dealer who can supply almost all the info you might need, manuals, and parts.

The modern high thrusts have a different gearing (I believe) not just the pitch of the prop.

Yamaha are very good engines, I have the modern high thrust 8hp four stroke Yamaha, very pleased with it.

Why do you need to overhaul it? if they are serviced annually and looked after they should not need over hauling, have you used it yet?

In my experience, the basic mechanics of these engines is very very good, elecs. can go wrong, and the biggest problem is water in fuel or oil.

Im very pleased with mine.
 
The modern high thrusts have a different gearing (I believe) not just the pitch of the prop
Click to expand...
Yes i am sure that's right. I had the figures on the screen earlier but this one is a 1990 they may or may not have offered the different gearing then.
 
Dan the man said:
email Yamaha Uk, they are very helpful. They will put you intouch with your nearest dealer who can supply almost all the info you might need, manuals, and parts.

The modern high thrusts have a different gearing (I believe) not just the pitch of the prop.

Yamaha are very good engines, I have the modern high thrust 8hp four stroke Yamaha, very pleased with it.

Why do you need to overhaul it? if they are serviced annually and looked after they should not need over hauling, have you used it yet?

In my experience, the basic mechanics of these engines is very very good, elecs. can go wrong, and the biggest problem is water in fuel or oil.

Im very pleased with mine.
Click to expand...

Basically it's been sitting for over 5 years in a shed, so just want to give it a good going over,
 
I have the high thrust version of a "white" Yamaha 9.9hp on my sadler 25 and have measured fuel consumption over two 25 mile trips at 2.5 litres per hour cruising at 5 knots
Have 40 litre tank which gives plenty of range
 
Yes it is
Serial number will be be F9.9AM (manual start) or F9.9AEM / F9.9AE (electric start) then a shaft length code (S, M, L) then 3 numbers then 6 numbers
High thrust reduction gear is 13:38, where as normal gearing is 13:27. Not much difference so a high thrust prop should put you very close to a full high thrust performance
I can very quickly accelerate to near hull speed but cruise at about 5 knots at about 1/2 throttle
 
I may be wrong but, from what I recall, all the early (white) F9.9AEL engines were sold as low geared, high thrust engines. We had one for years and I have recently sold it after it sitting in our garage for about 8 years. I had to clean the carb to get it to run properly.
If yours runs OK I would do nothing more than change the oil and filters. They are super engines and just keep going.
 
alahol2 said:
I may be wrong but, from what I recall, all the early (white) F9.9AEL engines were sold as low geared, high thrust engines. We had one for years and I have recently sold it after it sitting in our garage for about 8 years. I had to clean the carb to get it to run properly.
If yours runs OK I would do nothing more than change the oil and filters. They are super engines and just keep going.
Click to expand...

Thanks for that, having not seen it running I hope so!

PS had a good look through your website, really nice to read I'll be taking up some of your recommendations as I'll be keeping my boat in Portsmouth this year.
 
Yamaha may have changed their paint schemes since the late 80's, but when I was powering my 4000# 26 foot sloop for a decade with their 25" leg Hi Thrust 10 hp, it was white. Prop was a big three-blade, 11.75" diameter.

Unlike all the other gray color engines destined for little fishing skiffs, my series of engine - "Hi Thrust" - had a different final gear ratio (near 3 to 1 as I dimly recall) and drove our sloop at 6 kts for hours at a time on windless days.
Thrifty, too -- 1/2 gallon (us) per hour.
One of the best OB auxiliaries I have ever owned -- much better than the Honda 10 it replaced, and the Honda was a good engine.

Having the shifting lever out on the end of the tiller handle was very nice on a sailboat, btw.
 
The F9.9AE, is a high thrust model
I have workshop manual which gives gearing details
6G8 L 402963 the rest of serial number

Would sanction the bit about keeping fuel and carb clean, I will have to do mine this winter

Also check cam belt, should not be more than 10mm slack when pushed in at mid span between pulley's. Bit of a s.....d to get off as likely that bolts on alternator corroded into block, just take it very slowly with plenty of penetrating oil or see earlier thread on using lemon juice? to dissolve the corrosion.
 
Consumption

My later Yammy 4 stroke 9.9 does about 22 naughtycal miles per gallon at 5.5 knots in calm conditions pushing a 9.2 metre trimeringue.

Charging similar. It starts charging even at tickover and has never failed to provide sufficient amps for the requirements of the boat. Voltage goes up to 14.4 volts pretty quickly in normal use, which suggests that the charging circuit is providing all the amps the batteries can take.
 
9.9 Yamaha 4st

I had one of these a few years ago, on a 3.5 ton yacht. I seem to remember it used about 1.5 litres per hour at any cruise speed up to about 4.5kts. Top speed I could get in flat water and no wind, no crew, was about 6kts, certainly no more. Think at 5 kts and to flat out it used maybe 2 or even 3 litres an hour.
 
Yamaha 9.9

I would recommend owners keep the fuel tanks clean and filter replaced often. The jets are very small in the carb. For yacht use, suggest flush out with fresh water when you can to avoid lower case corrosion, and unscrew, clean and grease the battery cable connections every now and then. I found increasing corrosion in my conenctions which made it more difficult to start the engine. Be prepared for the ingnition electronics pack to fail, it is not uncommon.
 
Hi Seanfoster,

I`m using a 9,9AEL with my sailing boat 27ft, 2.6t since years.
Consumption is 1,3ltrs @ 4.5Knts, 2ltrs @ 5.3Knts and 3ltrs at max. RPM, which is ~ 4200RPM, giving the boat a speed of 6.5knts.

I have a complete service manual describing the "white line" of those types.
My own ist a grey one (the follower), basically identicaly, but with a different carb chocke and gear.
It was spoken that those grey ones are not consuming as much as the previous white ones, but I don`t know for sure.

The "coding" of types is absolutely confuse, it was right for the white ones but in some cases wrong for the grey ones. (Thrust or not..)

If you have any need for some copies from the manual, give me a ping via PM, I will scan in and send via email.

have fun,
Niels
 
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