2000-2001 Yamaha 70 - Unprecedented Problems

[TomRay]

I bought an old Yamaha 70 for my 15' Boston Whaler.

It starts up fine, but that's about the end of things it does fine.

When accellerating, just as the boat gets on plane, there is a sudden (like a switch was thrown) loss of power. If I keep advancing the throttle, it will go on and plane, but if I leave the throttle at a setting that was about to result in planing, it will fall back off.

When I open the throttle, it barely achieves rated RPM (according to one mechanic) and the boat goes 26 knots. It should be quite a bit faster than that, and the prop is a 15 pitch, which seems low to me.

When decelerating, just as the boat is about to fall off plane, there is a sudden surge of power. If I stop pulling the throttle back, the boat will get back on plane.

It has been to three mechanics, none of whom have ever seen this before. The carbs have been apart repeatedly. The CDI box was replaced.

This engine has been broken down and rebuilt. One mechanic was unimpressed that the wrong sealant had been used. The oil injection was removed by the previous owner. I put it back, but did not reconnect the cut wires.

I have a lot more money into this engine than it's worth at this point, and am ready to sell it for parts value and try again.

My goal here is to sell this boat. My wife wants a bigger one. I don't want to try to sell the hull or sell the boat with an engine that is not working right. Well, I wouldn't mind, but people don't want to buy bare hulls or broken boats.

Before I sell this one for parts and go searching for a replacement, has anyone ever heard of this before? Any ideas?

 

[99yam40]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

What kind of mechanics have you been taking it to?
My guess is not good Yamaha ones.

Sounds like it is dropping cylinders or timing is changing or there is a fuel/air mix problem.

spark voltages and timing are easy to look at at the different RPMs with proper test equipment, fuel mix is not easy.

replacing CDI does not say if voltage into and out of CDI is staying in spec or the timing is staying in spec.
And you have the coils and plug wires/caps and plugs that can be a problem

If wiring for oil system was not hooked back up as it should be there is a very good possibility things will not work properly

Have you looked at fuel pump to make sure it is not leaking fuel into crankcase?

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I don't know how to check the fuel pump. The mechanics seem to think the fuel system is OK and it's a timing problem. The changes in power are very sudden, so that seems plausible to me.

I've taken it to the kind I have available locally, but am running out. Do you know of a Yamaha mechanic in SW Florida who might be able to fix it?

What kinds of problems might the oil system wires cause? I thought they were for a warning buzzer.

 

[99yam40]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

if low oil level is detected or an overheat it will limit RPM to about 2 K along with setting off the buzzer, I believe it retards timing to do this on your motor as it does on my 40.

Timing light would show if timing is being changed

You can unbolt pump from block leaving hoses hooked up, pump primer bulb and see if there is fuel coming out of the pulse port.
may need a new gasket to put back on if damaged

http://www.yamahaoutboards.com/dealer-locator

find one with a master tech if you can

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I doubt it the boat plane at all if limited to 2k RPM.

One mechanic did use a timing light on it and said something about "base timing" mode. It was his idea to buy a new $638 CDI box, which changed nothing except my bank balance.

It seems that the dealership up in Port Charlotte has a master tech, but from what I've seen around there, they are focused on expensive new boats and four strokes. It doesn't seem like a place to take my cheap, old boat.

 

[99yam40]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

You need to find some one that knows Yamahas to work on it.
If you do not know how to test things and give info on what you are getting during the tests
the people on here are not going to be able to help much.

On my motor there is an idle and WOT timing spec, and at start up the timing advances some until warmed up this is all controlled by the CDI electronically, there is linkage to adjust some but have no idea on yours. So not sure what you are calling base timing on a motor that new

 

[Silvertip]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

There is also a process on outboards called "Link & Sync" (Yamaha may call it some other term). Engine ignition timing on outboards is synchronized with throttle opening. On two strokes this is especially important just because of the way these engines operate. Timing is used to control idle smoothness just as much as carburetion. Transition from idle to mid-range and high speed is also a function of throttle and timing. Just from your description it sounds like this may be a big part of the problem. Multiple carburetors on a two stroke must also be synchronized. Since you didn't say who "rebuilt" this engine, I'm going to guess the original owner did it and didn't know what he was doing when it came to proper setup. It is very common for a two stroke engine to rev up a bit when the throttle is chopped. That problem is always due to improper carburetion and is called "rpm hang". But for that to happen, lots of things need to be really buggered up in the fuel/ignition synchronization.

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

No one seems to like my idea of selling this engine for parts value.

Is that really so unreasonable? Remember, I have no emotional attachment to this motor at all. I want a working 70 hp on the back of my boat so it will sell. That's all.

With all the parts and repair bills, I'm into this engine for about what the boat would be worth if it had a working engine. The plan to use this engine to sell the boat is already a dramatic failure.

I can't escape the feeling that I could sink even more money into this thing and still wind up in the same place.

I figure I could get 500 bucks or so for this one, spend maybe 2k on a different one, and maybe get lucky enough to have it run long enough to sell the boat.

Is that a crazy plan?

 

[Silvertip]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

No one seems to like my idea of selling this engine for parts value.

Is that really so unreasonable? Remember, I have no emotional attachment to this motor at all. I want a working 70 hp on the back of my boat so it will sell. That's all.

With all the parts and repair bills, I'm into this engine for about what the boat would be worth if it had a working engine. The plan to use this engine to sell the boat is already a dramatic failure.

I can't escape the feeling that I could sink even more money into this thing and still wind up in the same place.

I figure I could get 500 bucks or so for this one, spend maybe 2k on a different one, and maybe get lucky enough to have it run long enough to sell the boat.

Is that a crazy plan?

Buying a boat or engine does not involve "luck". It involves due diligence. You are approaching this situation out of frustration rather than reasoning. You already have an engine that runs (sort of). So you succeed in selling this boat and/or motor (very likely for a financial loss) and buy another only to have jumped from the frying pan into the fire so to speak. There are no rules that say what you buy next will be any better than what you currently have, and may indeed be significantly worse. I take it you did not hear the current motor run or get an on-water test so let that be a lesson learned. Insist on it always. So the question arises, why risk throwing more money out the window. This engine can be fixed. The three mechanics are not mechanics if they can't figure this out. If you are incapable of doing any diagnostic work on this engine then I guess you are forced to do what you feel you need to do. But this is exactly the type of thing that gets people financially over their head when it comes to boating and can even cause family issues.

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I did hear the engine run before buying it, but only on land. Testing it first on water was not possible, or I would have done that.

It idles fine on land to this day. Looks very free of corrosion too. I figured it if looked clean and started up, it should work, or at least could be fixed. But that was a few thousand dollars and several fixing attempts ago.

The replacement boat will get a new engine with a warranty, so I'm not that worried about jumping from frying pan to fire.

I'm just concerned that by the time I get a mechanic who can fix this (assuming one can be found) to replace the cut oil tank wires and do whatever is needed to synchronize the timing, I'll have a repair bill larger than the projected $1,500 cost to just replace this engine with a running used engine. Old Yamaha 70s are pretty common around here. For example:

Yamaha 70 2 stroke TLRU 1997

 

[clanton]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

Check with Flagship Marine in Ponta Gorda. Ask for Hadley, if you can find him, he may direct you to someone that can fix it. I`m in Immokalee, a little far from, but I will do a basic check of all systems just for fun, may even have a manual. I would be concerned about the crankcase sealant and carbs.

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I thought Flagship did mostly sterndrive (car) engines?

Immokalee is only about an hour from me. I've already spent plenty of hours and a couple more won't hurt me a bit. I'd be happy to bring the boat down. I'm self-employed, so any time is a good time. My boss is very understanding about important boat-related emergencies. My cell is nine 41 then 62 eight and fifty one - seventy 7 at the end.

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I visited clanton yesterday and we think he may have found the problem, or at least a problem, with my engine:

The hoses around the oil tank and oil pump were interfering with the throttle linkage movement.

Could it really be that simple? I'm going to test run it in the creek in a little while and find out.

 

[99yam40]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

I do not think linkage interference would do what you posted at the beginning of this thread, but lets hope for the the best

 

[TomRay]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

Nope! We could see that the linkage interference was preventing the throttle plates from opening fully and fixing it did add a bit to the top speed of the boat, which got up to almost 29 knots yesterday. It should go faster.

It still has the same surging/bogging problems in the middle of the power range.

 

[99yam40]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

Was he able to get some spark voltage readings while running motor with and without the problem
or did you put it in the water to show him what it was doing?

 

[mrmamiller]

Re: 2000-2001 Yamaha 70 - Unprecedented Problems

Never had any work done by these folks, but if you don't mind a half hour drive, look up A-1 marine in Matlacha. Had friends take Yami outboards there for work and no complaints. A-1 is right next door to Miceli's Italian Restaurant. Stop in for a bite and a beer while you're there and it will make the trip worthwhile.