Injectors vs carbs

R

Roy & Dixie

New member
My 1999 22 CD has a 1999 F-80 (80 hp) 4 stroke Yamaha engine. Due to only 450 hr in 14 yr before I recently purchased the vessel, the carbs were dirty, gummed up, and needed cleaning. With a lot of advice and guidence from other C-Brats, I purchased an ultrasonic cleaner and cleaned the 4 carbs. The lower unit seals were leaking water in and lube out. I took the engine into a 5 star rated shop for repairs and to have the carbs balanced. While replacing the seals, the mechanic also found that the water pump was badly damaged due to having been run dry at some point in the past. It required a new pump housing as well as a new impella and other parts. I discussed the possibility of purchasing a new F-90 fuel injected engine. The 2 engines are the same except for the injectors and electronics. The new engine could connect directly to the existing instruments, so installation costs would be low. I was advised that I could get about $2,500 for the 1999 engine (sold by dealer on consignment) and pay @ $7,600 for the new engine.

The mechanic said the main advantage of a new engine would be fuel economy; that I could expect to use up to half the fuel. That would raise mpg from about 4 mpg to close to 8 mpg, which is a big streach, I feel. Does anyone have experience with moving from carbs to injected engine, everything else constant. I plan to cruise hundreds of hr a year for the next several years. With fuel costs as they are, I am considering the new engine. Would I actually experience a big improvement in mpg with a new injected engine?
 
The short answer is yes, you will have a marginally more reliable and better mpg engine with the injectors. HOWEVER, a well tuned carb engine will still get pretty good mpg and if well maintained will be very reliable. There is no way that you will experience twice the mpg making the move. 10 percent, maybe. You can buy a lot of fuel for your carbed engine for 7200 bucks. So beware, you may be having a sales pitch thrown at you in order to sell an expensive engine. There may be others with better comparisons between their carbed and injected engines. I'm basing my conclusion on what I've read and I read a lot about boat engines.
 
I agree with potter , you are not going to double you mpg in any way. 10 to 20 % at most. If you were going from a older two stroke then yes, but your not.

You have a good low hour engine that has been neglected a little. Once you have it running you will have no problems keeping it running. I would not spend the money just yet.

after re reading your post it looks like the mechanics said half again as much? That means a 50% increase not a doubling??? Its in the way people say things sometimes. I still think that number is high.
 
This statement...
Roy & Dixie":hy24jn38 said:
I took the engine into a 5 star rated shop...
Click to expand...

...is at complete odds with this one.

Roy & Dixie":hy24jn38 said:
The mechanic said the main advantage of a new engine would be fuel economy; that I could expect to use up to half the fuel.
Click to expand...

I'll refrain from injecting (ha!) opinions about the motor swap, but I'll suggest any mechanic who makes such outlandish claims can't possibly have your best interests in mind. A claim of such an MPG increase is beyond absurd - and more importantly, puts in doubt ANYTHING this person might advise.

Personally - I'd run, not walk away from such a shop.
 
I totally agree with what has been said above, and will add the following.

When I bought a new Yamaha 90 hp 2005 EFI engine when the EFI feature first came out, I paid about $7500 and got $1800 back after my much older engine and kicker were sold on consignment. So the price seems fair.

The EFI engine is less troublesome, runs smoother, starts easier, and does get somewhat better mileage, but you'll never recoup the cost in increased gas mileage.

Stick with what you've got, it's still 100% OK and just fine!

Joe. :teeth :thup
 
When I bought my boat, it had a Yamaha F80 on it with 50 hours. The carbs were obviously gunked up (it ran well at, IIRC, higher RPM but not lower). I had all four carbs rebuilt, plus a full service done on the engine just on principle (new impeller, plugs, etc.). This was not cheap, and, like you, I considered a new Yamaha 90 EFI. I have the round digital helm gauges that give a lot of info and would transfer right over to a new Yamaha.

The shop I went to gave me the opposite advice, in that they practically laughed at me (in a nice way) when I said maybe it would be better to just trade my engine on a new one. They heavily encouraged me to at least get out and try my F80 and only if I then didn't like it to come back and trade (their feeling was that I would love the engine once I used it). They said if it were them in the same position with their own engine they would stick with the F80, and that I should have many years and many, many hours left in it.

That's not to say that a new EFI engine would not be nice and would not have advantages; but the claim of such superior fuel consumption (which I know from reading here is not true) would put me off a bit.

My feeling in the end (for my particular engine) was that if I did buy a new one it would be purely just because I felt like it (not that that's not valid; the whole boat is just for pleasure, after all), and not for any practical "need" reason.

Sunbeam
 
Roy/Dixie,

I'm dying to hear what you do, since I happen to agree with the above comments. While Journey On has a fuel injected Honda, that's not always a blessing. I understand engines with carburetors, and I fiddle with fuel injection without understanding all those electrons.

The main reason for fuel injection is environmental constraints, NOT mileage. So I hope you keep that Yamaha, get it running right and enjoy your C-Dory. My only advice is to drain the carbs if you're not going to use it for a month or so. There are probably drain screws on the carbs. That said, I've left the ethanol gas in the Honda 150 for months at a time without any problems.

The next problem is to find an outboard mechanic who has your best interests at heart. If the 5 star mechanic is trying to sell an engine, he may not put his best efforts toward tuning your present motor.

Boris
 
Roy and Dixie,

I am running a carbureted Honda 90. I'd like to have an injected engine for better performance at altitude and easier cold weather starting, but other than that... I see little reason for spending the money to repower. If my engine was shot, I would definitely go with an injected engine, and may be even something like an eTec.

Steve
 
The 4 stroke Yahama is a very good engine. At 450 hours it has at least several thousand more hours in it--unless it has some problems with bearings or pistons etc-an series of oil analysis will determine that. Since you are planing hundreds of hours a year you can take an oil sample at each oil change, and in a year determine pretty well what the future of this engine is.

But for saving much money in fuel costs--you can make that much difference by properly trimming balancing and running your boat. Doubling the fuel economy (burning half the fuel) is just not going to happen. I agree that realistically you might get 10 to 20% better if all things were equal.

There are some minor disadvantages to Carbs, but as Boris says you can work on them and fix them if necessary. The fuel injection has multiple sensors and electronics--much more to go wrong, and if it does--you are up a creek. The newer engines have larger alternators, may idle slightly better and some may start easier--but my Honda Carb seems to start on every turn of the key--sure a little choke in cold weather.

Stay with the engine you have.
 
Just my 2 cents...

If I was buying a new to me boat that I planned to cruise more than just locally, I'd trade the old motor in and buy the new one.

I think if you run the boat often, the carbs are no big deal. We have had a few ski boats over the years (with carbs) and the only issue (and often) has been related to the carbs.

I don't think it makes sense financially, but when I'm at a far away location on vacation - I want that motor to start without any hesitation so it is worth the piece of mind to me.

Good Luck.
 
Decision also might depend on how much discretionary money you have at your disposal. The peace of mind in having a warranty and less likelihood of breakdown might allow you to enjoy the trip more.

We did have a previous boat with tons of bad experiences (inboard / outboard). It was so bad that we always feared what would go wrong on the trip. At one point, if we made it out and back without a problem, it was a good day.

Since that time, we have had better, more reliable engines which has resulted in a more enjoyable boating experience.

I dont blame you for wanting the new engine. We just cannot afford it to even be an option. Your finances may differ.
 
journey on":1oa4a6q4 said:
My only advice is to drain the carbs if you're not going to use it for a month or so. There are probably drain screws on the carbs.
Click to expand...

Presuming Roy's 1999 F80 is the same as my 2002 F80, then yes, there is a screw on each carb. I drained mine after the shop finished all the work and we sea-trialed it, because I knew I would be in project mode for some time and not using the engine. The bottom carb was a tiny bit fiddly to get to (although not horrible); the others were easy.

I'm planning to try to run non-ethanol fuel as much as possible, and then use the blue Stabil when necessary/medium-term storage. Also the ring-free sounds good.

Sunbeam
 
I can't imagine spending all kinds of money to have a perfectly good engine when you already have a perfectly good engine sitting on the back of the boat.......I honestly do not think you will notice ANY difference in the economy of a F/I motor over a carbed motor if the tuning is correct. I do think there is some, but I don't know if it is even calculatable. If what you have works, keep it!
 
Keep the existing engine!

Make a list of how you can spend the thousands of dollars difference on other improvements and accessories.

Compare the benefits of the unnecessary replacement engine to the list of goodies you could have for the same money.

Then decide.

If you buy the new engine instead, could you still afford to buy all the rest of the improvements?

How will you feel after you decide in either way?

Should be an easy choice.

Joe. :teeth :thup
 
I thank everyone for all the above comments, advice, and suggestions. It would be difficult to highlight any one post, since everything said by everyone is right on target to my original question.

The mechanic and I discussed the advantage of a new fuel injected engine 2 different times, his wording was along the line of 1/4 fuel comsumption in one discussion and 1/2 the fuel in another. In all fairness to the mechanic, I brought up the subject each time, even asking price, trade, consignment of old engine, etc. His office staff spent time on-line, to get figures on top, average, and trade value of the old engine. I was doing more to talk myself into a deal than he was pushing me toward one. But for my pursuing the question, I don't think he would have ever mentioned a new engine. I have the resources to get a new engine and continue to do many of the other things I'm sure I will do with/to the CD, but I have those resources due to not spending my hard earned money on anything unnecessary. In fact, I have skimped on many things the average person considers necessary.

The boat was in the shop for a week. I knew seals were bad in the lower unit and the carbs were on the list to balanced. When the lower unit was pulled, the water pump was found to be in terrible condition. It functioned, but was on it's way toward failure. So other parts had to be ordered from Yamaha, UPS does not deliver on Sat or Sun, parts had to be drop shipped from another location, etc, etc. I visited the dealer several times during the week and was allowed to hang around and watch while much of the work was being done. I was also discussing the possibility of them selling my pontoon boat on consignment. Actually, the mechanic put up with more than he would normally do for a customer. I was trying to justify a new engine, and he ended up giving me exaggerated estimates. The reason I started this topic was that if it sounds too good to be true, it probably isn't.

I sea trialed the boat for 30 mi at all RPM's yesterday. All is good. I will be keeping my 1999 F-80, as everyone has advised. I would never be able to justify a change even if I could save 10-20% on fuel. And I agree, I would probably see little, if any difference. I live in Fla and will be using the boat every few days, plus the long ICW trips to the Keys and Chesapeake Bay. so old fuel will not be a problem. I have over 300 mi and 50 hr since purchase just getting everything tested and running right (including several overnight trips and many pleasant memories). I seem to be ready for all my cruising plans.

Again, thanks for all the excellent input.
 
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