low rps 92 50 hp jet

[tweekster]

i have a 92 50hp ejrq, with the three light warning system, you know the green, yellow, and red lights on the motor, and the buzzer system in the control box. Just went out today and the oil was low, which triggerd the red light, but no buzzer, and according to the manual it drops the RPMs to 2000 RPMs. The boat is very slow (17' Polar Craft ) and tac in dash will only go to 2000 rpms, both before the red light, and during, basically no change. Added oil, light goes to green, still runs at 2000 rpms. When i came home and looked in the book it gave me a test for the buzzer, it is out, no buzz when 12 volt is added, my question is something keeping this motor from reving because the buzzer is not functioning or what could be wrong. Boat travels at 15 mph at 2000 rpm, and has since i bought it 2 days ago. this thing has to go faster than that

[tweekster]

Anyone? Really puzzled!

[tweekster]

Today I did some more work on motor, replaced warning buzzer and cleaned and checked oil injection tank on motor( only tank) pulled filter, looked great, and checked warning lights and buzzer for the low oil system, all test worked and lights and buzzer cam on as it should. Cleaned fuel filter, was clean nothing in there, and replaced spark plugs. Went to the river and tried it..... Rpms went up to 2500 and GPS speed for the boat was at 18 mph is something still wrong or is this all the faster this motor will push this boat? Book says max rpm for this motor is around 5000 rpm, I'm half that

[99yam40]

Sounds like you need to do a compression test on motor to start out with, then check spark with spark tester ,
Timing light will also show if good spark at upper RPMs and see if timing is advancing to spec.
Then it is on the fuel problems if all the other stuff checks out ok

Check to make sure tach is set properly and giving proper read out.

I believe a 50 jet is like a 35hp propped motor, might be a little light on that sized boat but sounds like motor is not running properly if tach is reading correctly

[tweekster]

Thank you for the info, compression is 110-120 in all three cylinders, warm, I am reading how to check timing tonight. Used a remote tack to verify reading while on the water, and 2400 is all it will do at WOT. There is no miss at all to the motor, no stumble, nothing. Starts first time, idles great, just no power. Any advice on checking the timing? I have done it on cars a lot, never a boat motor. Thank you, and all in advance for the help! Really bumming out that I bought this boat and it won't run well

[99yam40]

always run a boat before buying, it help to know how the boat will handle and makes sure motor runs well and does not have problems.

Timing on the OB is checked just like a car.
Mark the spot on flywheel where the proper timing spec is at idle and upper RPM with white pain or chalk, makes it easier to see out in the daylight

[tweekster]

Yea I know the try before you buy thing, but the story on this boat didn't allow me 2, I went through a lot of BS and paid very little, for a very nice boat! I'm just going to have to deal with some of the issues it brings.
Thank you
Ron

[rodbolt17]

carefully inspect the muffler tube.
they tend to corrode holes in them at the base of the tube.
will drive you nuts.

[tweekster]

Rodbolt17, will that make the motor run at low rpms? I'm guessing I would have to pull the jet lower end to see that?
Thanks
Ron

[tweekster]

Thanks to all that helped, and added advice, turned out the seat and needle in the middle carb had serious pitting, some backyard drill work, and was flooding the carb. But not that I have it running well, I still am only at 3200 rpm, gps tells me I'm at 24 mph top speed, is it possible with the jet pump this is all the rpms I will turn? Motor is running great through out idle to wide open.

[99yam40]

here is some info from web site that may help
16. What can cause RPM to be too low or too high?

Load has nothing to do with RPM on a jet drive (see question number 4, 11). Impeller pitch and diameter is based on sea level operation. At higher elevation, you will lose RPM and may have to drop down one impeller size. Long use in corrosive conditions may create pin holes in the exhaust tube which builds up back pressure and reduces RPM. Excessive RPM is usually caused by air entering the pump. It can be caused also, during start up, if the leading edges of the blades are blunted from gravel. A rough boat bottom, keels or damage ahead of the intake can introduce air, as well as setting the motor too high.


Here is a link so you can read more if you would like Outboard Jets - Make Every River Longer