20' Javeliin-200 Venom-Slow Hole Shot

[peatmoss96]

I have a 1994 Johnson Venom 200 with a 4 blade Renagade prop which was rebuilt 13 months ago. The boat has been run monthly since the rebuild including proper break-in. A month ago the engine began to loose power on take off, like the boat was full of water(it wasn't). I have checked the following systems/components:<br />1.Compression 90-95 on the left bank,90-110 on the right bank(110 was sleeved on rebuild); 2. Carb settings, jets, float settings and all fuel flow locations at carbs clear, fuel filter; 3. Plug wires good, no double firing, plug gaps good, no fouled plugs; 4. Timing both idle and WOT settings good; 5. Syncronization ok; 6. No appearent cracked fuel lines or tranfer hoses. <br /><br />The power pack was replaced 2 months ago during a tune up procedure but the trigger coil tested ok (Repaired by certified mechanic). I am leaning towards a fuel restriction but the engine does not hesitate, just lacks power under load during takoff. The top end speed is not completely there but is not as noticeable, 62-67 now and 70-75 new. <br /><br />Just looking for direction on whether it may be the trigger coil, power pack or fuel(pressure, sucking air, or restriction in carbs). The motor is not popping back, missing, loading up, or surging, just no power like before. <br /><br />I enjoy working on the engine and am trying to fix it without using a boat repair service.<br /><br />Thanks for you time in advance.

 

[Dhadley]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Welcome!!<br /><br />What spark plugs are you using? What's the wot timing set at?<br /><br />Are the outer magnets in the flywheel OK? What about the inner hub magnet? <br /><br />Why did the motor have to be rebuilt?

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Spark Plugs are QL77JC4 Champion<br /><br />WOT timing is 19 deg BTDC<br /><br />Don't know about the magnets, all look good on visual inspection, non loose.<br /><br />The engine was rebuild after dropping a cylinder. The mechanic who performed the rebuild said it was due to carbon build-up. He ringed all the cylinders, built carbs, sleeved #3 and complete overhaul.

 

[Dhadley]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Thats a tad much on the timing but if you're jetted right it'll probably be OK. Just be careful. Good choice on plugs. Whats the top rpm with an average load?

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Top rpm at WOT is 5800 to 6000 on top end. Under load I haven't looked, what would be a good range? Motor seems to build RPM's slowly until on plane. Forgot to add plug gap of .030.

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Dhadley,<br /><br />Any other ideas? Currently I have started looking at the prop. The boat has a 13 1/2 X 25 4 blade Renagade with lots of wear. I am looking to rebuild it and begin there.

 

[Dhadley]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

OK, you say the top rpm is 5800 to 6000 but you haven't looked under a load. What's that mean?

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Went to the lake today. Before I left, changed all fuel filters on the boat and the fuel/water seperator. Put in new plugs. I ran the boat on the lake and it seems I may be on to something. With the new filters, the engine ran alot better, got up better. Not quite the hole shot I am looking for, but ran better. I think that it has been starving for fuel. Flat out it runs 62 mph at 6000. I think that is to many rpms. <br /><br />To answer you question above, I haven't watched the tach while taking off, but I have looked at while traveling full speed. Would that be considered under load? If so, then 6000 is the #. <br /><br />The timing you spoke of earlier, should that be backed down to 18 deg? Would the timing be the best way to control the top rpm or can I correct this with a recondition on my tired prop?

 

[todd foster]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

hey peatmoss.I have a 99 model sprint 207 f/s fish and ski with a 98 model johnson venom 200.My top speed with a renegade 3 blade prop is 69 mph. at 6150 rpm.I also have a hydraulic jackplate but don't know how much of a differenc that makes.Just wanted to give you a reference that's all.Good luck on your omc journey.

 

[Dhadley]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Nothing wrong with 6000. You're not close to the rev limiter. Why do you think that's too much?

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Well, the target range seems to be around 5800, does more rpms decrease engine life? It runs good at 6000, just seemed a little on the high side. <br /><br />When you spoke about the flywheel, how do you check it? Also, a friend said that the reed valves may need to be inspected, they may be causing poor performance.<br /><br />I have been able to get a little better hole shot by providing better fuel flow and installing fresh plugs. I have also moved the ground wire on the power pack to a better location. <br /><br />The next approach I think I will make will be to recheck the flywheel and then the ignition coils.<br /><br />What do you think?<br /><br />Thanks

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

Thanks for the help, ended up building the carbs and think that got it. We will see this weekend.

 

[peatmoss96]

Re: 20' Javeliin-200 Venom-Slow Hole Shot

To close the subject, built carbs, and replaced sensor coil under flywheel. Boat runs good as new. Problem was identified by picking up eratic firing throughout RPM range, started from there.

Thanks for the help