Acceleration problem

[jaydub]

I've had an intermittent problem with acceleration on my GW 222 with a 250 HP Yamaha. It runs really great, but once in awhile, when I'm running for a while at at cruise speed around 4000 rpm and I back off and run at a lower RPM (around 1200 RPM's), I can't get it to accelerate beyond 3300 RPM's when I try to get back on plane. It just will not accelerate beyond about 3300 RPM's. If I stop the boat, shut off the engine and restart it, it works just fine ands accelerates normally. It doesn't happen all the time; just occasionally.

I recently had an annual service and they thought it may have been a clogged fuel pre-filter so that got changed out. But when I ran it for a while yesterday I had it happen again. It doesn't happen all the time; it's intermittent. I'm going to take it back in but it seems like it might be something electrical the way it resets after shutting it down.

Anyone ever seen this or have any suggestions on things to look at?

 

[seasick]

I've had an intermittent problem with acceleration on my GW 222 with a 250 HP Yamaha. It runs really great, but once in awhile, when I'm running for a while at at cruise speed around 4000 rpm and I back off and run at a lower RPM (around 1200 RPM's), I can't get it to accelerate beyond 3300 RPM's when I try to get back on plane. It just will not accelerate beyond about 3300 RPM's. If I stop the boat, shut off the engine and restart it, it works just fine ands accelerates normally. It doesn't happen all the time; just occasionally.

I recently had an annual service and they thought it may have been a clogged fuel pre-filter so that got changed out. But when I ran it for a while yesterday I had it happen again. It doesn't happen all the time; it's intermittent. I'm going to take it back in but it seems like it might be something electrical the way it resets after shutting it down.

Anyone ever seen this or have any suggestions on things to look at?

Electrical is possible, perhaps as something gets hot. The issue may be related not so much to revs as is is to the bumpiness of the ride. Check for loose cable connections at the motor ( especially the ground). Electrical aside, first I would suspect a fuel issue. You may have blockage or a tank vent issue. Check to see if the primer bulb is collapsing when the issue arises. If so, there is either a vent blockage, a bad fuel line, clogged pickup or bad anti-siphon valve. Bad primer bulbs are also possible but rarer. Make sure that the bulb gets firm when squeezed wit the motor off.
You might have a clogged VST screen (assuming this is a 2 stroke). Other than opening up the VST tank and inspecting, the only other reliable way to test is to measure the fuel pressure at the VST. These motors can have fuel issues when being bounced around if the VST screen is dirty/clogged.
LP pumps could be weak causing fuel starvation too. If you run with the cowling off and if the issue arises, quickly look at the motor mounter clear fuel bowl. If mostly empty, you have a fuel starvation issue. If full you have an air leak. The bowl is normally 1/2 to 3/4 full. There are other filters on that motor too that could be partially blocked.
Let us know what you find

 

[Parthery]

It's a 4 stroke (F250) according to his signature....

Given that it resets when you restart it, it sounds electrical to me....

 

[jaydub]

Yep, it's a 4 stroke. They did change the pre filter and the primer bulb since they were thinking it was fuel related too but that didn't fix it. Taking it back in next week so they can look at it and run it. The problem is, it is intermittent so it's difficult to get the problem to show up or know for sure if it's fixed. When I find out what's going on I'll let you know.

 

[seasick]

It's a 4 stroke (F250) according to his signature....

Given that it resets when you restart it, it sounds electrical to me....

Oops. Missed that F250 signature

I am curious why you suspect electrical if thew motor works after shutting off and then on?

 

[Parthery]

My experience has been that a fuel system problem will still be there after a restart. Electrical problems tend to come and go and a reboot or restart sometimes resets whatever was going on. Highly unscientific and based only on limited experience. As the expression goes, YMMV..... :grin:

 

[wspitler]

I'm betting on fuel. Any restriction, maybe intermittent, could cause reduced flow, therefore lack of acceleration. There are several places that could empty due to a restriction. Water separator filter, primary fuel filter, and the vapor separator tank that holds the high pressure pump and vst filter. After shutting down completely, fuel could refill. I'd drain the VST and change the filters, both the engine mounted and the VST filter. There have been some HP fuel pump failures as well. Just a guess.

 

[jaydub]

I took the boat in for service and they hooked up a computer to the F250 and took it out and ran it. The computer showed it was a bad cam position sensor. I understand when these go bad they can limit the acceleration. They replaced the sensor and took it out and ran it again with the computer and no problems. I ran it today for about an hour and tried to recreate the problem by slowing down, then speeding up and it ran great-no problem. So it looks like that was the problem. Glad they were able to diagnose it like that. Now time to get back to fishing!

 

[seasick]

I took the boat in for service and they hooked up a computer to the F250 and took it out and ran it. The computer showed it was a bad cam position sensor. I understand when these go bad they can limit the acceleration. They replaced the sensor and took it out and ran it again with the computer and no problems. I ran it today for about an hour and tried to recreate the problem by slowing down, then speeding up and it ran great-no problem. So it looks like that was the problem. Glad they were able to diagnose it like that. Now time to get back to fishing!

Great news. I will keep that in mind next time a similar issues comes up.

 

[Daman858]

Cam position sensors are a buga-boo in so many engines, marine or otherwise. I had the same issue in my Yamaha F200 and my Ford F350 Power Stroke diesel tow vehicle at he exact same time. Yam was on warranty, Ford was a recall...no expense but lots of head aches.