Throttle cam roller

[trebor135]

I hate to go on this long, but I want to be sure I give all the info. 2000 Johnson 150, 6 carbs, purchased used from a pair. I got the counter-rotating motor. I have been trying to determine if I am acheiving full power. I got a brand new Faria service tach and have been trying to get the right prop. The guys at Stiletto and many folks here think I am not acheiving full power. By everyones calculations the prop I am running should be a little underpitched and I am only achieving 4900 rpms @ wot while nearly trimmed out to a rooster tail. I first did a compression test by the OMC manual directions. Range from 95 to 102 psi. That seems ok I guess. I moved on to carb / throttle linkage stuff. I noticed an amber colored roller sleeved over the black throttle cam roller. I can't determine if this is something that someone added trying to get the butterflys in the carbs to open up more. It looks like a piece of hard, sort of transparent yellowish colored tubing. If I remove it, the butterflys are not quite straight out. After reading the manual a little further, I got to the spark advance roller section. It says that the throttle cam roller and the spark advance roller should engage at the same time. This wasn't happening. My theory is that someone added this roller to open up the throttle more without taking into consideration that they would be retarding the timing. I adjusted the spark advance roller where it made contact at the same point that the throttle cam roller made contact. Made a test run. It seemed like I had much better power at takeoff, but I made no gains at top end. I am trying to determine if I should remove this extra roller and set the timing roller back where it was. My next attemp before I break down and take it to a mechanic is to remove the high speed jet screws in the front of the carbs and blast them out with carb cleaner. Will this do any good or will it just dead end and blast back at me?
Thanks for any feedback,
Rob

 

[HighTrim]

Re: Throttle cam roller

When were the carbs last rebuilt and bathed? It sure might be time. As far as the cam roller, could you take a pic of what you are referring to. I assume you dont see it in the tutorial diagrams in your manual? I would clean and rebuild the carb, perform a link n sinc and set up your throttle and choke linkage,throttle cam, etc... as per your manual.

 

[Joe Reeves]

Re: Throttle cam roller

Year back, the throttle roller was simply one piece of hard rubber (or some kind of material). In recent years, some idiot decided to change that to a small hard black roller covered by a clear plastic sleeve which brought the roller to the proper diameter.

Bad move.... that clear sleeve just falls apart. Purchase a new roller.

 

[mikesea]

Re: Throttle cam roller

As Joe said the plastic piece you think may have been added,is factory,and fuel,heat both?cause it to fall apart,but your right,without it the carbs dont open like they should.Depending o your set up,you are not far off.5000-5500 if I recall right.So ,lets split the book spec to 5250.your off maybe 350 rpm,at WOT,I'm thinking its a prop problem unless someone did retard your timing ,by toying with the adjustment on top of the intake.You dont want to advance it to the point it could detonate the piston.I recall guys retarding a few degreesin he 80's because of fuel problems etc.If your sinc and link is right,butterflies open all the way I think a different prop.Wha kind of hull do you have,could you have a weight problem due to water in hull floattation?dirty bottom.As for the jest.The high speed jets are inside carb ,behind the bottom plugs,but,if you had a plugged jet ,your rpm would be worse,the high speed jets are pretty big,if carbs were dirty,you would likely have ideling and strting issues.This is all just my opinion,and I do need more coffee.

 

[MarkV_Deep6]

Re: Throttle cam roller

I hate to go on this long, but I want to be sure I give all the info. 2000 Johnson 150, 6 carbs, purchased used from a pair. Rob

The roller you are talking about should stay. Do a proper Link and Sinc on the carbs. You do have a manual? Who did the Prop calculations for you? What size boat is this and what is the hull rated for in HP?

The engine was just mounted correct? I would suspect the hieght of the engine may be a contributing factor. It would be nice to have some pic's.

 

[CharlieB]

Re: Throttle cam roller

Try a couple more compression test using different gauges.

Some gauges read slightly different than others.

Your readings seem uniformly low, although J/E did build a string of low-compression motors I think that ended about mid-90's or before.

If indeed all gauges read in the same area, the motor starts and runs well enough, then down size the prop SLIGHTLY cause your rpm is very close to fine.

 

[trebor135]

Re: Throttle cam roller

Let's see if I can cover everything. I do have the omc service manual but I don't have the testing equip to do a timing and sync job. At least I know now that the roller is factory although it is cracked. The only thing I did was make sure that the throttle roller cam and the spark advance roller made contact at the same time as the book said. It said that as you move the throttle forward that they should begin to move at the same time. I have no way to test to see if I am 20 deg. before tdc at wot. The boat is a 2008 19' Seachaser offshore series. No waterlogged or dirtyhull problems. It is however a wide, deep v boat for a 19'. It has a 103" beam and max rating is 150 hp. I'l try to post some pics of the mounting height. I do have another (brand new) compression gauge and I'll try that again. What is an average compression for this motor? A tech guy named Steve that works at the stilleto prop factory has been doing the math for me on the prop. Ron 7000 over on the prop forum agrees with the math. It seems that they are using the same type formulas which are over my head. Gear ratio (1:86 for mine), speed, rpms etc. Ron 7000 feels I should use a 3 blade instead of 4. I talked to a local mechanic today and he said that this model boat is a slug and hard to push. (The sacrifice for a good ride I guess.) Maybe thats the only problem. I'm probably going to let him do some testing on the motor to see what he thinks. I'm sure I'll tinker with it some more before then. $$$!
Thanks all!
Rob....

 

[HighTrim]

Re: Throttle cam roller

What is important is that your compression readings are even across all cylinders, within 10 percent of each other, not the actual reading. All meters read a bit differently, although Id imagine youd be in the 100 psi range across the board. A good decarb will be able to even out the readings if need be, just check the FAQ for the procedure.

 

[MarkV_Deep6]

Re: Throttle cam roller

Let's see if I can cover everything. I do have the omc service manual but I don't have the testing equip to do a timing and sync job.
Thanks all!
Rob....

You really don't need any special equipment to do a link and sync. Just read the manual on this. It's very easy, not much more involved than adjusting what you already did. The roller outer lining was probably there when the timeing was set. If the roller no longer has the outer rubber lining, or is partially gone, this will affect timeing and throttle position. That's why it should be replaced. Putting everything back to orriginal condition may give you more RPM.

 

[jtexas]

Re: Throttle cam roller

I thought this was in the Engine FAQ section, but it's not....found it anyway:

quoting from Joe Reeves...

(Timing At Cranking Speed Less 4?)
(J. Reeves)
The full spark advance can be adjusted without have the engine running at near full throttle as follows.

To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).

Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.

I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28?, set the timing at 24?. The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?.

If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4? which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.

No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.

 

[Joe Reeves]

Re: Throttle cam roller

The 200 model incorporates the Fast Start feature (automatic spark advance) when starting. The above timing procedure will not work and will give false readings UNLESS you're capable of disconnecting that Fast Start feature temporarily.

 

[trebor135]

Re: Throttle cam roller

I got me a can of Seafoam and I'm gonna decarb the girl tomorrow. Is it ok to to decarb on the hose or does she need to be under a load? Plus, has anyone figured how to disable the faststart so I can use that timing procedure on my model?
Thanks Rob..

 

[HighTrim]

Re: Throttle cam roller

You can do it in the driveway , but remember it will smoke like heck and drip goo all over the driveway, so might want to do it later at night if you have neighbours This is the technique reccomended by TD. In a portable tank, mix 3/4 gallons of premix gas, an 3/4 can of seafoam, (assuming you don't have the vro connected). Put the remaining seafoam in a spray bottle, run the motor up to temperture, remove the plugs, one at a time, spray some seafoam into each cylinder and replace plug. Let it sit 15 minutes, remove the air silencer from the carb while waiting, restart motor, and spray seafoam into each carb, until it start to stall. Repeat until the seafoam is gone. Run out the remaining gas. Replace the plugs with new ones, and then do the compression check again. This procedure burns the carbon out of the motor and been known to free up rings and increase compression. Let us know what you find.

 

[jspringator]

Re: Throttle cam roller

Does a small amount of wear on the old hard rubber rollers make any difference?

 

[Joe Reeves]

Re: Throttle cam roller

Gator....... No, just make sure that the adjustment pertaining to having the scribe on the cam being aligned with dead center of the roller when the throttle buterfly(s) start to open.

 

[trebor135]

Re: Throttle cam roller

I tried to follow the decarb instructions in the FAQ posted by gss036. I mixed 3/4 gal of gas and 16 oz. of seafoam. I ran the motor for 15 min @ idle and guess what? It sucked down all of the gas except for a little splash. That made it kinda hard to repeat the process 2 more times being its a pretty far peice to the nearest auto parts store for another can. I did however have a can of deep creep and after I let it sit for 15 min., I sprayed in the cylinders and carbs. Let it sit, and sprayed it again. I guess it done the job. Followed up with another compression test. Gained about 2 psi on each cylinder. Still ranging from 97 to 105 psi overall. I can't get over it sucking down nearly a gallon in 15 min. at idle. Think it's time to visit a mechanic.
Thanks guys,
Rob..