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I have a 95 Yamaha wave venture 700 that i bought a couple

weeks ago. When I...
I have a 95 Yamaha wave venture 700 that i bought a couple weeks ago. When I got it and put it in the water i noticed that it wasent running right. It would bog down if you gave nailed it, but if you rolled into the throttle it would go. I also noticed that it seemed to have poor acceleration and top end power. It seemed to be hitting the rev limiter on the top end but I could tell it wasn't topping out where it should. Also when i accelerated it seemed to slip as it tried to gain speed. I knew it was a partial carb problem so I cleaned them and droped it back in the water. It ran alot better with almost no bogging what so ever, however it was still slipping on acceleration and hitting the rev limiter on the top end without ever topping out, then after having it in the water for a few hours it began to run like crap again. It would bog down on acceleration and would not go over 25 mph. Also it would not gain rpm's over half throttle, power was the same from half to full throtte
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Answered in 11 minutes by:
7/27/2009
RSRBOB
RSRBOB, Technician
Category: Boat
Satisfied Customers: 1,078
Experience: Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M
Verified
HiCustomer
There are a few things I am going to have you look at.
First, I would like you to start with a compression test. You should have 155 psi on both cylinders. When you check it, make sure you leave the other spark plug installed. Having it out will lower the readings.
As long as the compression is good, the bog you are describing sounds like a lean hesitation. If you hit the throttle hard and nothing happens, like the engine just goes flat for a moment, then you need to turn the low speed screws out 1/4 and try it again. You don't want to go out any more than needed to remove the hesitation. If you get them out too far, it will tend to load up in extended idle zones. I try to let it idle in a straight line for thirty seconds, then whack the throttle wide open. The engine should respond instantly, without a hesitation or blubber.
If it blubbers, it is too rich and you will need to go in on the low speed screws 1/4 turn. If you pick up a lean hesitation when you go in 1/4, back them out 1/8. The fuel mixture screws are very sensitive so 1/8 of a turn can make a difference.
The part you described that sounds like the engine is revving up but the ski is not accelerating sounds like a worn jet pump impeller. If the ski had been operated in waters less than 2 feet deep, it was pulling sand off the bottom and running it through the jet pump. This wears the aluminum impeller. You will have to replace the impeller to resolve this issue. Skat Trak, among others, make stainless steel replacement impellers that offer increased durability and some improvements in performance. If you plan on keeping the ski for a few years, I think it would be worth investing in the stainless prop.
The part about it loosing top speed after it has been run a few hours doesn't sound good either. If you are not getting any warning lights or signs, then the compression test again would be an immediate necessity to diagnose that problem. This could be a sign that the engine is having internal problems.
If you have any more questions, feel free to ask.
Thanks
RSRBOB
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Customer reply replied 8 years ago

I checked the compression in both cylinders the other day, one was at 150 and the other at 145.

 

I also wanted to mention that out of the water the ski runs like a dream, no bogging or hesitation what so ever, it idles perfect. Could it still be a carb issue if it runs so good out of the water?

 

Also I am not sure if this is any help but the last time i had it on the water after cleaning the carbs for a second time, it seemed to have a miss when cruising at higher speeds (while at the highest speed it would go anyway, which was about 25 mph because it was not running right) any ideas on what this could have been?

Thank you for the additional information.
If the compression test was post 25 mph max speed, ok. If you tested the compression before you took it out and rode it and it only ran 25 mph, then you need to test it again.
Some more questions, is it smoking? That engine does not have a variable ratio oil pump so it should be smoking rather noticably. Especially during extended idle periods.
The bogging or hesitation could definitely be carburetion. In fact, if the engine is mechanically sound, I am almost positive it is a carburetion issue.
The lean hesitation is something I call the baaaa WAAAAAAAAAA's. That would be when you hit it wide open from a standing start and nothing happens, or a worse case scenario where you hit it and it stalls. That would be lean and shows a need to open the low speed screws 1/2 turn and re-test.
If it is trying to accelerate but blubbers, like it is stumbling over itself as it builds revs, that is a rich condition and you should turn the low speed screws in 1/2 turn and re-test.
The other symptom you eluded to was the slipping, that is almost assuredly the prop being worn beyond service limits. What nails that down for me is the statement that you made saying you could ease it up without slipping, but could not hit it hard without slipping.
When you are cleaning the carbs, are you inspecting the check valves for the fuel pump? If so, what are you looking for? How is the internal fuel filter looking? How about the high speed air cut valve? Also, did you stick a finger into the intake to check to make sure all the reed petals were there?
The high speed miss is concerning as well. It could be a carb issue, too lean too. Exactly where did you set your high and low speed mixture screws when you put the carbs back together?
It sounds like we have a lot going on here, and we may need to address it one problem at a time.
Let me know!
Thanks
RSRBOB
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Customer reply replied 8 years ago

The compression test was done after the 25 mph top speed, which is good.

 

And it is smoking which is also good.

 

I adjusted the high and low speed screws to the service manual specs, it was 5/8 for #1 and 1 1/8 for #2 on the high speed, and 5/8 on #1 for the low speed. The #1 and #2 in the service manual refers to each carb right? I figured #1 front carb and #2 back carb?

 

I am not sure what you are refering to when you say check valve for the fuel pump...is that the float? The internal fuel filters seem clean, and no i didnt check the reed, but i will now.

 

Also as far as the high speed miss. What screw would i adjust to correct this, or would this fall into the low speed adjustment that i have to try out?

 

I would really like to try this out tommarow and see how it goes, so if it is ok with you i would like to wait to accept and see if i have any other questions i come up with after my adjustments. If this is cool by you, i would surly throw you a bounus for all the help youve been. Let me know if this is fine and thank you very much for all the assistance.

Again, thank you for the additional information.
Frankly, I find the compression readings disconcerting. Although not horrible, it could still be indicative of a problem. There is no good reason for a deviation of 5 lbs.

You are correct about the carbs being 1 and 2 front to rear. You didn't specify the setting for the low speed on #2 however.

The high speed setting is ok, but I have found that leaning out the rear hi speed can clean up top end RPM's a bit. It is not a necessity. I believe Yamaha is using the additional rich mixture to aid in cooling the rear cylinder.

The high speed miss is probably not a fuel screw adjustment. If you wanted to experiment, I would lean out the rear high speed screw to about 7/8. It is definitely NOT going to be affected by the low speed fuel screw adjustments.

The fuel pump portion of the carb is on the opposite side of the carb as the float arm and needle valve. The check valves are the round mylar pieces in the center aluminum block. What you are looking for is to make sure they are flat and sealing all the way around. When the engine hydrolocks, it forces water backwards through the carbs and creases the check valves for the fuel pumps. This reduces the efficiency of them since they are not sealing @ 100% due to the creases in them. If you find any creases, you will need to replace them. It does require a close look, but upon close inspection, the creases are plain to the naked eye, no need for magnification.

The high speed air cut valve was a bit of a test for you. I was trying to determine how closely you looked the internals over. It is the oblong shaped (or rounded rectangular) mylar on the inside of the half moon shaped aluminum covering the high and low speed jets. It too can crease and allow air back into the high speed circuit causing it to lean out.

Definitely check the reed valves out when you have the carbs and intake off. You should be able to feel each petal with your finger.

Make sure you have NGK spark plugs that are not fouled. A fouled spark plug cannot be cleaned to save money or cut corners. Once a plug fouls, it will never be the same. It may last for a little while after cleaning, but will foul again very soon.

Check to make sure both vacuum lines for the fuel pumps do not have any cracks or holes in them that would reduce the engine pulses to the fuel pumps.

Also, check the rear main seal on the crank (in front of the couple for the intermediate shaft) to make sure they have not blown out and are rattling around on the coupler shaft.

If you don't find anything else, you may still have a carb problem. You could also have a compression problem as well. If you cannot find anything wrong in all of the areas previously touched upon, you may have to pull the head off to inspect the cylinder bores and pistons for damage.

You never directly said you were not getting any warning lights or sounds, so I am assuming you are not. Therefore it cannot be going into the return to port overheat mode.

As far as paying, pay when you feel I have helped you, and pay what you think the advice and direction are worth.
Thank you,
RSRBOB
RSRBOB
RSRBOB, Technician
Category: Boat
Satisfied Customers: 1,078
Experience: Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M
Verified
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RSRBOB
RSRBOB
RSRBOB, Technician
Category: Boat
Satisfied Customers: 1,078
1,078 Satisfied Customers
Experience: Former Yamaha Factory Service Rep, Dlr Line Tech, Serv Mgr, G/M

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