4K RPM max and will not go over 30.

[Scotttheimpaler]

I think Dr. Honda was talking about triggers and butterflies, I don't even know where those are. As for the trigger, I have stuff under the flywheel, don't know what all is there. I have a late 2001 engine OE386969 - pre alternator if that helps.

 

[Sportster-2001-951C-Stock]

Sorry, I thought you had mentioned your throttle body butterflies had stuck open and even though they were fully open the engine would only run at low speed (roughly). I lose track easily, lol

The trigger is a series of coils around a laminated steel plate and works like a transformer. There are a series of magnets on the inside of the flywheel and while it spins around produces a voltage in the trigger coils that tells the ignition switch boxes when to fire the ignition coils. This is all in time with the compression stroke of the cylinders as the flywheel rotates so the ignition takes place at the right moment.

You should see a lever that reaches up to under the flywheel and is moved by the throttle linkage, this lever is attached to the trigger coil in such a way as to cause it to move. This moves the trigger coil in relation to the crankshaft thus advances the ignition timing mechanically as throttle position increases. If the trigger coil isn't being moved (not advancing, for whatever reason) as the throttle is increased, spark ignition is late in the compression stroke resulting in considerably less power due to the fuel is ignited too late.

Fuel burns at a pretty stable rate and as engine speed increases, the fuel must be ignited progressively earlier in the compression stroke to gain maximum combustion pressure.

Thus if the mechanical throttle linkage isn't moving the ignition trigger coil under the flywheel to advance the ignition timing then power will suffer due to the fire is ignited too late to maximize cylinder combustion pressure.

Thanks for S/N, I'll take a look and confirm yours has this trigger coil linkage, later models this was done electrically and until I see one in front of me it's hard to know which configuration you have.

There are several things that can go wrong relating to the ignition timing and unfortunately most of the parts are pricy so it's worth while spending the time to diagnose.

 

[Sportster-2001-951C-Stock]

Item #15 in this drawing is the ignition trigger that generates the voltage used to trigger the ignition coils at the optimum position in the compression stroke. As the throttle is advancing there's a linkage that connects to this trigger assembly under the flywheel causing it to rotate slightly, maybe an inch or so, as the throttle plates open.

So make sure the linkage is moving and isn't damaged. Be careful not to rotate the adjustment pieces (turnbuckle(s)) or the timing afvance will be changed from factory settings and a timing light will be necessary to reset the timing while the engine is running.

You can disconnect the linkage if necessary to check for binding action then reconnect without changing the geometry of the linkage adjustment pieces.

https://www.mercruiserparts.com/Sho...esc=Electrical+Components(Flywheel+/+Starter)

Item #1 of this 2nd link is the throttle body. This is where the throttle butterfly plates are located. The butterflies are round disks mounted on a shaft the rotates as the throttle is moved, their position controls the amount of air that can be drawn into the engine during the intake stroke. When open fully, maximum combustion air can enter required to make maximum power.

At throttle idle position these butterflies will be nearly completely closed, keeping air from entering throttling back the amount of air the engine can breath.

If you open the helm throttle fully, these butterflies should be at a 90* angle to the intake air flow, for maximum intake air.

Say for instance your throttle cable is broken (there are some plastic pieces here and there that can break) the butterfly plates may not be opening fully due to limited throttle cable travel.

So you can pull that front cover off and inspect the throttle butterfly plates to confirm they are reaching full open as the helm throttle is in full throttle position.

Probably you can simply see the external bell crank attached to the throttle butterfly shaft move to it's full open travel position but there's no better way to confirm all butterflies are completely open than by laying your eyes on them directly.

https://www.mercruiserparts.com/Sho...nbr=5387&bnbr=50&bdesc=Fuel+Management+System

 

[Scotttheimpaler]

I have not messed with the TPS yet, the long list of "part no longer available" is not encouraging. Ill check the compression and the TPS area on Saturday or Sunday, the rest of my evenings are spoken for until then. I should have my port side temp sensor by then as well.

I have seen the trigger before, and it look okay at the time. I had to replace the stator and flywheel. One of the magnets came off the flywheel and got lodged in the stator, destroying them both. I found a newer flywheel with a ring inside keep this from happening again.

Where does this engine pull air from? Does it have an air filter? I've never been able locate one.

 

[Sportster-2001-951C-Stock]

You can back probe the TPS connector to measure the DC voltage while operating the throttle. I prefer using my (el-cheapo $5 Harbor Freight?) analog meter for this b/c it's easy to see if the needle jumps around near a dead spot. I use a couple of diaper pins to back probe the connector, slip the sharp end up into the connector to avoid damaging the silicone seal gaskets.

Yep, just make sure the trigger rotates with the throttle linkage. If not, the mechanical ignition advance isn't working.


While the flywheel was off and stator replaced it's important to not disturb the linkage adjustment of the trigger position to avoid throwing off the ignition timing.. This can cause cause low performance if retarded timing or too much advance will cause piston-eating detonation. A timing light is used to adjust this linkage with engine running.

There's no air filter on boats per-say, b/c there's not much dust. (There are some exceptions perhaps but air filters are unnecessary, spark arrestors are necessary. Thus there's always a flame arrestor to avoid fire in the bilge in case of a backfire or lean sneeze that could ignite bilge fumes.

The flame arrestor cover in this case is item #15 of the second link drawing. If you can remove this cover you'll see the round throttle butterflies underneath and will be able to confirm they open fully 90 degrees with full throttle.

Quite right about the flywheel, sometimes problems can occur with the magnets.

 

[Scotttheimpaler]

I was in the midst of changing the port side temp sensor and noticed that one of the tan wires were not connected. I must have disconnected it wire replacing the pickup pump. Could this be the source of my issues? I hope so, I'll find out tomorrow.

 

[Dr Honda]

yes and no.

Smoke and hard starting will be caused by it being disconnected. But as I said before... it won't keep the engine from reving up to full power.

 

[Sportster-2001-951C-Stock]

FWIW, You can check the resistance of the various sensors using an ohmmeter to confirm their reasonable values, here are a couple of charts I happened to rediscover on one of my local drives. For example, at 25*C ambient the air temp sensor should measure about 7.5K Ohms:

 

[Scotttheimpaler]

Update: I went to install my port side temp sensor and noticed one wire was disconnected, it would appear that when I replaced the Pick up pump the wire got disconnected and never reconnected. I installed the new part and all 3 wires . I hoped this was the problem, seemed like a smoking gun at the time. Took it out last night, still only runs around 35 MPH but the smoke is gone.

So back to the TPS and comp testing.

It will probably be Sunday before I can work on it again.

 

[Dr Honda]

The lift pump is just to feed the engine after it's been sitting, and only pumps when you are cranking the engine. When it's running... there is a mechanical pump that feeds the fuel injection system. AND... since the EFI has a tank full of fuel (for the high pressure system) it's almost not even needed. Normally, the only time you know it's gone bad, is when there is another issue, and you need to re-fill the VST.


And... once again... the TPS isn't going to make a difference with your problem.

One thing... instead of telling us your top speed... what's the peak RPM?


Go right to a compression test.

 

[Sportster-2001-951C-Stock]

Compression test is always the first thing I do on a 2-stroke (FWIW)

The manual I attached has a troubleshooting section.

 

[Scotttheimpaler]

UPDATE: took it to the ramp several weeks ago, no start. Noticed the lift pump wasn't running so i changed the separator. Still no start. So I took it home and parked it. Later I got in to replace the last 2 fuel lines, I was waiting to do them with the separator. While replacing the lines I noticed the large wire harness below the separator had come apart, so i put it back together, replaced the last 2 fuel lines on the boat, and put in clean plugs gaped to .060 as the engine cover recommends (I had been using .040 I read on-line somewhere). It started right up.

Took it out, was hitting 50+ MPH.

In the end, I replaced about 10-11 feet of 5/16" EFI fuel line, port side temp switch, and put in clean and correctly gapped plugs, and ran out over 1/2 a tank of bad gas.

 

[Dr Honda]

Was that the main (round) engine connector?

Regardless... I'm glad to see it running again.

 

[Scotttheimpaler]

yes, round, has 7-10 pins, maybe 1-1/4 in Diameter. hides under the separator near the starter. I must have knocked it lose while changing the separator in the field.

 

[Dr Honda]

Yep... that would do it. LOL