Yamaha HPDI 200 Problem Please Help!

Hi all,

I recently purchased a Yamaha HPDI 200 for my 19’ center console. The motor has 100+ compression and is within 10% range in all cylinders. After purchase I installed new spark plugs, new racor filter, and new fuel filter (the one before the LP pumps). It ran great for a few trips and then began developing the following problems:

1. On a choppy day and with a lot of weight, it began to surge at higher RPMS and the rpm’s would fluctuate slightly. I then took the boat out with less weight and it still had the same issue but not quite as bad. I did a lot of research and reading from this point forward.

2. Before taking it out again I purchased the YDS software. With the ignition on and engine off, all of the readings looked to be within range. I had a replacement VST filter and gasket so I changed those and then took the boat out for a test. All of the numbers and data on the YDS still looked to be normal. However, the engine would not get above 1700-1800 rpm. If I left the throttle all the way down it would eventually start to climb slowly and get on plane. I was hesitant to put it above 3200rpm.

3. I then did a throttle synchronization and TPS adjustment and checked the spark plugs. The motor now wouldn’t hold idle. It would die out after 5-10 seconds. I changed the low pressure pumps, high pressure pump mystery filters, and 3 fuel injector filters. I also cleaned the oxygen sensor. Now the motor would idle fine but still would not get above 1700-1800rpm.

I plan on changing the medium pressure filter (the metal canister) and remaining 3 fuel injector filters but I’m not optimistic these will solve the problem. The VST and High pressure pump psi’s are within the range of the manual. All 6 cylinders are firing according to YDS. Shift position switch is working as it should according to YDS. What are the chances that plugging in the YDS shorted or messed up something with the ECU? That seems to be when the 1700rpm problem started. Oil tank and sensor seems to be working appropriately. No alarms or codes on YDS.

When I initially plugged the YDS in, I noticed that the engine hours was only 68. The guy I bought the motor from had a pair (the other one had low compression which is why he was selling them). He was very helpful and I’m sure he would give me whatever parts I needed from the other motor. I find it odd that an 18 year old motor has 68 hours so the ECU might have been replaced at some point, I’m not sure. But it was running fine for the first week or two I had it and would get on plane with no problem or symptoms.

I have read of a somewhat similar problem caused by the exhaust tuner, however it seems to be few and far between. I have not checked it because I keep the boat in the water and do not have a trailer at the moment. Is there a way to get a better idea if it may be the culprit before I go hunting down a trailer?

I have not checked the voltage output of the fuel pressure sensor because my fuel sensor readings seem to be okay and I do not have a test harness. Is there another way to test the fuel pressure sensor? I have checked the fuel pressure regulator and that was within spec.

Any help would be greatly appreciated!!

Check the shift switch

Years ago I had a similar problem with a Mariner. I thought that my fuel tank was clean so I discounted it and checked everything else.. Turned out there was a bit of water in the tank. Cleaning the tank and new fuel fixed the problem.
Good luck.

I don’t know if you will even read this but I am giving it a try. Have you figured out your problem? I a m having the same problem. My first Yamaha and my last!!!!

Hi Terry, Sorry to hear about your problems. Real frustrating. Yamaha's are good reliable motors and probably have the world's larget market share.
I had a problem with a 15hp Mariner that turned out to be water in the gas. Wasted a lot of time and money on that.
My other issue was with a 20hp Yamaha that is effected by excess fuel vapour pressure in the VST. I didn't find any one issue was the cause. I changed the solenoid valve on the VST and keep my gas fresh and cool.
Your initial problem almost sounds like water moving around in your fuel tank. My motor ran fine until hit plane. The water would move to the pickup and the motor would lose RPM but not die. Just ran like crap. If I was real slow on the throttle I could get a bit of speed but soon as the water moved to the pickup the rev.'s would drop. I pissed around with plugs, carb. etc. Turned out to be a little blob of water.
I'm sure it's something simple. It's just finding it.
Good Luck.
Roblin

What is strange about it it was running fine. Scooting across the water at 4800 rpm the just like pulling the throttle back down to 1800 . It would start and run fine but only 1800 rpm. But then it got to where it won’t idle. If I try to throttle it up in neutral it dies but if I hurry up and put it in gear and throttle it up it will run but not very well. Wats strange it runs better with number one spark wire unplugged don’t run at all on 3&4 . Has good spark on both.

Sounds similar to my experience with the water. I have a portable tank that I had emptied in the fall for storage. I the spring I filled the empty tank with fresh gas and headed out. At low speed the bow was high so the fuel pickup was also high. When I throttled up and went up on plane the bow dropped down and the tank leveled out. There was a little ball of water in the tank and when the tank was level it would work it's way to the fuel pickup. That was enough to drop the rpm to an idle. The bow would rise and the water would move away from the pickup. After a bit the motor would run fine again. Of course when I gave it throttle, the whole problem would repeat.
Thinking back, the motor would occasionally die. If it died, it would be hard to start. If I backed off full throttle soon enough, the RMP's would drop and eventually the water would clear, but the motor wouldn't rev until it did.
The other thing I found was, depending which spark plug wire I pulled, the motor didn't seem to notice. I ran a 9.9 Johnson that had a wire off and it seemed to run smooth, just not lots of power.
On the Mariner, I did a carb. kit, fuel pump, spark plugs, fuel hose, fuel connectors, switch box and fuel. Drove me nuts.
Turns out it was a little blob of water. About a table spoon size when I found it. Got rid of the water and the motor ran like a champ.
If you have an inboard fuel tank, and don't have a means of trapping water, there may be a blob of water moving around in your tank.
These motor are built to take lots of abuse in remote places and keep running. I'd guess, that the chances of something seriously wrong on a motor with 68 hrs are pretty low.
I know that the vapour pressure problem I had on the Yamaha kept eluding the mechanic at the dealership. There was nothing to find. The dealer told my to try high test gas. The motor is suppose to run on regular and the price of high test is prohibitive. In hind sight, switching to high test may have fixed the problem.
I bought my first boat and motor when I was young. The fellow that owned the marina was and old "sea dog", kind of guy. My plan was to go down every pay and give him money until the the outfit was paid for and I'd pick it up. He said to take the boat and motor and use it while I was paying for it. No paperwork, just a hand shake.
Before I did, he got serious and looked me in the eye. He said, " son, I want you to know. A boat is just a hole in the water to throw your money into".
He was right. I wanted it, I did it, and I've been feeding that hole ever since.
Good luck

I will try the remote fuel tank. The one thing I don’t understand is why it will run some what in gear with some throttle but not at all with throttle only. I know the last thing I do to it will fix it . LOL

I tried the remote fuel tank. Still don’t run. I have tried a different injector drive module and a different ECU I have checked wires .