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My mechanic gave up! Need HELP!

S

SScape

New member
Hi guys. I have a 2005 Yamaha Model F200 V6 It is HPDI version and is mounted on a 24’ Sailfish WAC. This engine has less than 600 hours on it.
My problem is that the engine runs absolutely fine until I get to around 3500rpm and then it races. I will post a video here to show you. My mechanic seems to have given up on me now having made me change propellers to brand new 3 different times, plus I put a brand new lower unit on it just last year. Guess what, the problem remains and I am looking at another summer stuck under 3500rpm. Can you guys take a look and offer advice on a course of action other than a hand grenade under the cowling, because trust me, I am there.. Turns out I cannot post the video, it’s too large.
The issue is that when I reach approximately 3500 rpm the motor races on it’s own and accelerates to full rpm WITHOUT propeller acceleration. It is like the motor disengages and races until I move the shifter back. Then, I can accelerate normally again until I reach 3500 rpm again.
 
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How long have you owned this boat?----Salt water ?----What is the water temperature ?------Is the motor a long shaft or extra long ?-----Post the transom height measurements here.-----To me it sounds like motor is mounted too high.----This issue should be so easy to solve.
 
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An F200 won't be an HPDI model. F is a four stroke. All HPDIs were two strokes. Z or VZ prefix.

How high is the unknown model mounted? Any transducers or thru hull fittings located forward of the lower unit?
 
Thanks Guys - you are right. --to be exact this is a 2005 Yamaha Z200TXRD Here is the serial number- 6G6X1020793 It is definitely a 2 stroke HPDI. My mechanic has gone through the motor extensively.
I have owned this boat going on 4 years. Prior to that it was used by another guy for occasional use during our fairly short season on Cape Cod. When I bought it, it had less than 500 hours on it. This has nothing to do with where the engine is mounted. It is not the prop either. I have uploaded a video to youtube to show you and here it is:

The main point you have to understand is that when I move the shift lever up past 3000 rpm, the engine starts to accelerate on it's own, first slowly and then it gets past 4000 rpm and then it races as if I jammed the shift lever to full throttle, but there is no more forward momentum. Again, I am not touching the throttle at all. Last year we installed a brand new lower unit and trim & tilt assembly. At this point I wish I didn't because I could have saved that for a new motor instead but when I have a Yamaha with less than 600 hours on it, I assume that it is worth saving.
I grew up on boats, I know a lot yes, but I am not a mechanic and this is way beyond my ability to solve. I feel like this is a sensor or switch or something like that effecting fuel injection. I am very frustrated and clueless and done grasping at straws. Any help you can give me is very much appreciated,
 
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Some want to argue.----Propeller is losing grip I say.--------Motor mounted too high I think.------Find a competent shop to sort this out in minutes !
 
SScape said:
Thanks Guys - you are right. --to be exact this is a 2005 Yamaha Z200TXRD Here is the serial number- 6G6X1020793 It is definitely a 2 stroke HPDI. My mechanic has gone through the motor extensively.
I have owned this boat going on 4 years. Prior to that it was used by another guy for occasional use during our fairly short season on Cape Cod. When I bought it, it had less than 500 hours on it. This has nothing to do with where the engine is mounted. It is not the prop either. I have uploaded a video to youtube to show you and here it is:

The main point you have to understand is that when I move the shift lever up past 3000 rpm, the engine starts to accelerate on it's own, first slowly and then it gets past 4000 rpm and then it races as if I jammed the shift lever to full throttle, but there is no more forward momentum. Again, I am not touching the throttle at all. Last year we installed a brand new lower unit and trim & tilt assembly. At this point I wish I didn't because I could have saved that for a new motor instead but when I have a Yamaha with less than 600 hours on it, I assume that it is worth saving.
I grew up on boats, I know a lot yes, but I am not a mechanic and this is way beyond my ability to solve. I feel like this is a sensor or switch or something like that effecting fuel injection. I am very frustrated and clueless and done grasping at straws. Any help you can give me is very much appreciated,
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What is the prop diameter & pitch? Have you checked the prop to see if the hub is still firmly attached? I asked the same question about a friends' boat with a different hull (his is one of the old Regal Cat deck boats) and the problem was easy to cause by shifting weight forward. They were using a slightly dinged stainless prop, but repaced it with Aluminum- the motor seemed too high, but I was told it hasn't been removed/reinstalled.
 
The engine was doing this before the new lower unit was installed? What did the driveshaft spline look like on the old lower unit? What doesn't make sense is that despite the engine RPM increase you say that forward motion doesn't increase (speed stays the same, correct?) You have validated that the engine is not ventilating or a spun hub, and tried a different propeller with the same result? It seems to be happening when the boat is about to break plane. Have you recently installed a new depth finder transducer that could be setting up a slip stream in front or near the propeller area? Does this engine use electronic throttle controls or use a TPS to manage the throttle body?
 
fitz73222 said:
The engine was doing this before the new lower unit was installed? What did the driveshaft spline look like on the old lower unit? What doesn't make sense is that despite the engine RPM increase you say that forward motion doesn't increase (speed stays the same, correct?) You have validated that the engine is not ventilating or a spun hub, and tried a different propeller with the same result? It seems to be happening when the boat is about to break plane. Have you recently installed a new depth finder transducer that could be setting up a slip stream in front or near the propeller area? Does this engine use electronic throttle controls or use a TPS to manage the throttle body?
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Yes it was doing the same thing at the exact same point in rpm/acceleration every single time.. There was nothing wrong with the other lower unit. I replaced it for no reason in an effort to fix this problem. "despite the engine RPM increase you say that forward motion doesn't increase (speed stays the same, correct?)" Yes, it stops pushing the prop..it is as if I threw it in neutral and revved the motor. I have tried 3 brand new props. 2 aluminum and one stainless that came with the boat that I had re-hubbed. I did not install anything new through the hull or otherwise. I am lost on your last question. Sorry and thank you.
 
racerone said:
Some want to argue.----Propeller is losing grip I say.--------Motor mounted too high I think.------Find a competent shop to sort this out in minutes !
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Nope 3 perfectly good props tried and the boat was used for years with the engine as it is mounted.
 
Were you ever in this boat when it ran normally without this issue? Can you take a side view picture of the engine height relative to the bottom of the boat and the typical trim angle you run normally and post it.
 
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SScape said:
The main point you have to understand is that when I move the shift lever up past 3000 rpm, the engine starts to accelerate on it's own, first slowly and then it gets past 4000 rpm and then it races as if I jammed the shift lever to full throttle, but there is no more forward momentum. Again, I am not touching the throttle at all.
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Is there a separate lever for both the shift function and the throttle function? Sounds like that is the situation.

The only time the motor is to be shifted into and out of gear is at idle RPM.
 
boscoe said:
Is there a separate lever for both the shift function and the throttle function? Sounds like that is the situation.

The only time the motor is to be shifted into and out of gear is at idle RPM.
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Boscoe, I think its just a matter of description, it has the standard single lever remote control in the video. The engine isn't going into neutral it's just going back to idle in gear. I'm just trying to determine if this is a mechanical issue or an ECU engine controls issue. Strange for sure. Can't wait to drill down to root cause.
 
Had a fellow call me many years ago.-----A 1973 model 135 HP Evinrude doing the exact same thing.-----I asked him to measure the transom.----No response on that.----He insisted I take his lower unit apart.----Found nothing wrong.----He reluctantly measured his transom.----I told him to cut it down by 1-1/2"-----No more issues.-----He then bought a rebuilt motor from me with total confidence.
 
The boat ran normally when I bought it and for the years that 2 previous owners used it. I am the one owner that this issue came up on. It is not transom height or props. I appreciate you even thinking about a solution for me. FYI here is what seems like the best response (to me anyway) from another forum so far: The runaway of the engine can be fuel or electronic. In the first case, for whatever reason ( and there are several) more fuel than needed is injected into the motor. This can be a sticky injector , a computer issue or a problem with high pressure fuel delivery. The speedup could also be a problem with the throttle position sensor but that seems less likely to me. Monitoring the high pressure fuel pressure may shed some light on the problem. I am not sure if that motor has overspeed (revs) protection but it looks like it does based on the way it throttles down.
 
Good luck with the issue !----These lower units can not --" slowly jump out of gear "-----Your engine speed / rpm is going up as load on the prop is reduced.
 
I just looked at the photo in post #1 and it shows 0MPH @ 3000RPM- does this have digital control of throttle, shifting and gauges, like the Mercury DTS? If the systems are similar/same, the point needs to be made that in the Mercury DTS, the tach is the 'brains' of the operation and that can cause all kinds of problems.

At the end of my first week working at a boat dealer, a big pontoon boat was there and the shop manager was working on it- he would shift into forward, reverse or neutral but there was no way to know how it would react.
 
jimn said:
I just looked at the photo in post #1 and it shows 0MPH @ 3000RPM- does this have digital control of throttle, shifting and gauges, like the Mercury DTS? If the systems are similar/same, the point needs to be made that in the Mercury DTS, the tach is the 'brains' of the operation and that can cause all kinds of problems.

At the end of my first week working at a boat dealer, a big pontoon boat was there and the shop manager was working on it- he would shift into forward, reverse or neutral but there was no way to know how it would react.
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The gauges are crap. The only one I changed so far is the fuel gauge because I was working on a fuel issue as a possible problem in this and ruled it out. MPH isn't connected.
 
Being that it's a 2 stroke I'm wondering if a vacuum leak might be metering in extra air causing it to race. I had this on a 2 stroke snowblower engine, worth throttle shaft on the carb caused it to rev wide open. New carb fixed the problem.
 
What happens when you move the throttle control handle past that point while the engine is acting in this behavior?

Do you have an engine service manual to help try and guide you a bit more?… looks like you ought to have manual part number LIT-18616-02-82.

Here would be your part’s catalog for the engine model to browse through if needed as it may help spread ideas too of an open mind…,
www.crowleymarine.com

Yamaha Motors Outboard 2005 200hp Z200TXRD [Z200TXRD] - Parts Lookup | Crowley Marine

View parts diagrams and shop online for Z200TXRD : Yamaha Motors Outboard 2005 200hp Z200TXRD. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.
www.crowleymarine.com www.crowleymarine.com
 
Fun Times said:
What happens when you move the throttle control handle past that point while the engine is acting in this behavior?

Do you have an engine service manual to help try and guide you a bit more?… looks like you ought to have manual part number LIT-18616-02-82.

Here would be your part’s catalog for the engine model to browse through if needed as it may help spread ideas too of an open mind…,
www.crowleymarine.com

Yamaha Motors Outboard 2005 200hp Z200TXRD [Z200TXRD] - Parts Lookup | Crowley Marine

View parts diagrams and shop online for Z200TXRD : Yamaha Motors Outboard 2005 200hp Z200TXRD. Offering discount prices on OEM parts for over 50 years. FAST $4.95 shipping available.
www.crowleymarine.com www.crowleymarine.com
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I have to say that I never moved it past because I was afraid the engine was being damaged, and it sounds like it is going to explode. It's knee jerk to pull it back I am sure you understand too. I also think that would have done nothing because the engine isn't listening to the control input once this point is reached. That's the other weird part of this issue, the forward momentum stops. It is as is I am racing the motor in neutral. Thank you for the manual. I know my mechanic doesn't have one and I may as well buy one at this stage. Very helpful, the manual has been ordered, thank you.
 
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If possible it would be interesting to hook up a vacuum gauge to a source of manifold vacuum to see what it does under different throttle settings
 
Here's my solution: I am repowering with a brand new Mercury 200XL. Thanks for your considered advice guys. Admin thank you. You can close the thread.
 
Definitely on odd issue. Not likely, but maybe the spline at the top of the lower unit would slip in the crankshaft end?
Either way, best of luck with the new engine.
 
R_P said:
Definitely on odd issue. Not likely, but maybe the spline at the top of the lower unit would slip in the crankshaft end?
Either way, best of luck with the new engine.
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Thank you. I put a brand new lower unit in last year in an effort to solve it that way but no. There was nothing wrong with the one that was in there. Now I am thinking about taking that new one back out and selling it before my engine is wholesaled off for next to nothing. Not sure if I can recover much from that or the new tilt/trim assembly I put on at the same time. Virtually new and I wish I didn't spend it now of course. Ugh- boats. We are all nuts!
 
SScape said:
Thank you. I put a brand new lower unit in last year in an effort to solve it that way but no. There was nothing wrong with the one that was in there. Now I am thinking about taking that new one back out and selling it before my engine is wholesaled off for next to nothing. Not sure if I can recover much from that or the new tilt/trim assembly I put on at the same time. Virtually new and I wish I didn't spend it now of course. Ugh- boats. We are all nuts!
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Before you replace things, make something turn. The whole drive can be made to turn by putting a wrench on the flywheel nut and holding the propshaft with the tool and another wrench. If it doesn't turn while shifted into gear with a lot of torque, there's nothing wrong with that part of it, mechanically.

If the new lower has little use, you should be able to get a decent price for it, rather than losing your shirt.

Do you hear any strange sounds when it loses drive, like grinding or clanking?

Contact Merc technical support and find a well-trained and certified servicer- before leaving it with anyone, ask A LOT of questions about rtaining for the service techs. The dealership SHOULD display the diplomas for anyone who works there and passed the training courses and hands-on training. If you see more names than mechanics, ask who has left- many dealers display all of the diplomas whether someone works there, or not.

Ask the dealers if any of the mechanics has worked for a manufacturer- some have and they move around the country after they leave.
 
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