RPM hesitates around 3500

[wakehead]

I'm a new owner of an Epic SX in Denver and have recently encountered a problem.  When the boat is heavily loaded, it has trouble reving the engine above 2500 RPM.  If relatively lightly loaded, the RPM won't go above 3500.  Once 3500 RPM is established, the RPM will back off to about 3000 before reving up to 3500 again.  Despite the throttle's position, the RPM will continue to fluctuate.  There are no "knocking" noises, however the tranmission seems noisy and hot to the touch.  I think the problem lies with the transmission, but would like to know if anyone has had similar problems and solutions.  The transmission is hard to fix and expensive.  Shall I look into the spark plugs and/or fuel pump before the transmission?

[wakehead]

Just update. I changed spark plugs, and found that they are covered with oil, and can see pool of oil in the spark plug holes. Apparently, oil is leaking thru ,and I think short-circuiting the current, igniting at the different places of the spark plugs at higher rpm. I am going to take it to Lexus mechanic, and have him look at it.

[Rambling Wreck]

I haven't chimed in as you are way above me when it comes to diagnosing a problem such as the one you describe. There is also a thread from another member that describes oil on the plugs as a problem. Apparently this is a vexing issue to even the pros here or they are all out on the lake for the past few days. Keep us informed of what you find out. It sounds scary but hopefully turns out to be something easily remedied like most of the issues with these boats.

[toyotafreak]

One of our members discovered that overfilling the engine oil even a little caused oily buildup and fouling in a couple of the cyclinders.

[PSullivan3]

I just started reading this thread are you using synthetic oil?Because sometimes synthetic has a tendency to bleed through the gaskets ,in the past when this has happened in cars (nice ones )I would change out the oil and substitute 5-20 or whatever the engine called for along with STP blue bottle (12oz) make sure it is warn before you put it in ,and it cleared after driving it.Now I don't work on foreign engines,but I think this is universal.

[wakehead]

Update.  A Toyota mechanic changed the rubber gaskets surrounding the spark plug entrance, fixing the oil leak problem.  I have changed the fuel filter, placed high octane gas, but the engine still sputters around 3500 rpm.

Today, I removed the prop and ran the boat in water and found that the engine will not rev up past 4000 rpm.  The engine starts vibrating and sometimes the engine stalls.  There are no boat dealers in Denver that will look at my boat.  I need help.  Does anybody have any ideas?  Thanks.

[masonlk]

fuel...filter & fuel replaced. follow Capt Rick's instructions for testing pump.
air.....not likely unless something is blocking intake.
spark.plugs replaced. coils? check all wires under dash. these boats have done some weird things
 ? ? ? ?when wires are loose at the ignition or somewhere else.

does it run smooth(normal) at idle to 3500?
vibration-motor mounts all tight? just engine or whole boat?
turned off battery switch and re-set computer? sorry,had to ask.
most of this, if not all, is probably redundant but maybe it'll help you think of something.
the 3500 thing is strange...my best guess is computer at this point.

[Ktown]

I just changed my plugs and found a similar situation (oil in the plug cylinder).  I only have 2 or 3 plugs with any oil in the plug cylinder. however, I took a picture of the worst one.  Can't see how this would effect too much as it is obviously a very small amount of oil.  After cleaning it out the best I could, I plan on keeping an eye on mine and seeing if it leaks any more.  If so, I will try to change the gasket.  Anyway, here is the picture for those of us who are visual learners!

[westtx]

K-Town, our Toyota dealer in San Angelo owns an Epic and his techs are used to working on it. Give me a call at 713-417-2904 if you want, and I'll give him a call and see if he can take a look at it.

[wakehead]

I just rechecked spark plug holes again, and found 5 of the holes were filled with oil like Ktown's Epic. Apparently whatever Toyota mechanic repaired-replacing spark-plug gaskets-did not work. This is likely be the problem of high rpm sputter, i think, as much oil is causing abnormal ignition at high rpm. Hey, K-town, how is your boat running at high rpm? I am having the same Toyota mechanic taking another look. will let you know.

[lesman01]

I thought there was only a crush washer on the plug? Is there another gasket?

[Ktown]

Wakehead,

Excellent at low and high RPM, although my WOT is only 4600 RPM. ?I have no known problems with mine. ?I wouldn't have found it if I hadn't changed the plugs! ?I only have one plug like the one you saw in the picture, but 2 others with just a hint of oil. ?How deep is the oil in your plug cylinder? ?Which cylinders are leaking? ?Mine is the last one on the starboard side (vdrive) closest to the oil dipstick. ?It's obvious that the oil is leaking from around the top of the plug cylinder on mine, and I would assume it is the  head gasket (very slow leak or spot that leaks at specific conditions). ?These gaskets can be very painful. ?If they aren't put on just right, they can leak. ?Perhaps your mechanic can shed some light on what he finds? ?Has anyone done this job themselves? ?I plan on monitoring mine for the next few weeks to see if it gets worse or stays the same. ?With the amount of oil I found, I don't know that it is effecting the plug at all? ?I'm definitely not a mechanic, but unless it was enough oil to make it up to where the plug cover connects, it shouldn't cause the plug any problems? ?Anyone else have an opinion?

Westtx,

Thanks, I will give you a call if I decide to take it to a mechanic. ?I am trying to get my hands dirty as much as possible, but if I start having noticable problems I will give you a ring to save the day. ?Again, thanks for all the help. ?

[wakehead]

Toyota mechanic told me that spark plugs should be relatively dry whereas mine were covered with oil along with holes filled with oil- about the same amount as KTown's. He said too much oil in  spark plugs will mess up ignition as RPM rises. He replaced all 8 of ring gaskets( i am not sure what there are actually called) at the top of spark plug holes, but that did not fix the problem. We will see what he says again. This may be the reason why your wot may be stuck at 4600. My problem is I can not rev beyond 4000rpm. But again I have 5 spark plugs (2+3) covered with oil instead of 1.

[Capt Rick]

Do a compression check When you run the boat disconnect the hose PCV going to air filter. If you have a bad cylinder there will be alot of bypass smoke gas. Publish the compression.

[Ktown]

Makes sense, which is why I changed plugs.  I wanted to ensure I was getting all 8 cylinders of power.  Did your plugs fill up after one run?  Seems strange, where did the oil go previously (assuming you ran it multiple times with the leak)?  It would eventually fill the plug cylinder entirely!  Do you think your leak is that sever?  Looking forward to hearing what your mechanic finds/thinks is causing the leaking!