I have a problem with getting up to full rpm with crusaders 350s in 1981 Silverton 37. I talked to Mark head engineer for Silverton and he said my boat came with 20 x 23 props. But right now I have 20 x 21 and barely making 3200 RPM. Converted the distributors to electronic ignition, and I am getting full advanced at 3000 RPM at 30В° BTC. I'm not getting any bog down from the carbs, I have full compression at 150 psi on all cylinders. The only thing I did not check was the exhaust system. I did notice that the valve lash is about 1/8 of a turn before the pushrod start to spin freely. I will be adjusting them this weekend on one motor since that one had the beginnings of a burnt valve in it. I scoped out all cylinders and only had one head with two valves being black on both engines the rest of the valves nice and tan. I am rebuilding both heads and replacing all exhaust valves since all of them are pitted on their edges. The bottom is nice and clean and the prop shafts seem to be in complete alignment. Any other ideas, is it possible I'm missing something. On the carbs, and I will say up front I am a Holley guy and 0 experience on Q-jets, I am making about 2600rpm on the primaries alone. And I forced open the upper secondary air flap and tried to run by opening the secondary's slowly, but it did bog down then. I'm getting fuel because I have hit the throttles wide open from a standing start and it kept running with out any bogging. Any help out there would be appreciated.
37 Silverton RPM issue
- Thread starter Cbeinc1
- Start date
With apologies to Charlie, I'll fire off a suggestion shotgun filled with random questions and WAGs and see if anything lands or possibly helps you think of something else:
Both engines are now limited to ~3200 RPM, yes? And spec WOT RPM is 4200-4400, right? So it there might be some possibility 2 cylinders on each engine are not firing (correctly) *
Have they been limited that way ever since you have had the boat? How long?
When you advance the control throttle levers underway, do the engines reach 3200 at ~~3/4 of full lever travel, or not until the levers hit the WOT stop? [ Possible cable adjustment needed to fully open the throttle plates? Have control cables (or controls) been replaced without checking adjustment?]
Have you had the "20x23" props prop-scanned to see what you may really have on there now?
Are the props and hull quite clean or is there substantial fouling? Is the boat sitting lower relative to the painted w/l than it used to? ( compartments with excess retained water?)
Keep in mind , a 37' motorboat can get a LOT heavier due to many factors over 36 years and that alone could require even less prop pitch. And if by any chance by "350s" you mean the 350 c.i./270 hp Crusaders and not the 454 c.i./ 350hp engines, those would be under a lot of strain already to power that boat. 454 c.i.s , yes?
*Suggest trying attaching a timing light inductive pickup to successive plug wires to confirm each cable is carrying ignition pulse.That doesn't necessary mean those cylinders are firing , or at the right time.
*Have you triple-checked firing order for each engine? Plug cables all have continuity?
Standard LH rotation engine as viewed from flywheel end toward the pulley end: 1-8-4-3-6-5-7-2 .
Opposite RH rotation: 1-2-7-5-6-3-4-8 .
(Both LH & RH distributors turn CW.)
(DON'T judge engine rotation by prop shaft rotation, unless you know for sure the reduction gears do not have reverse output like mine have.)
What kind of distributor conversion kit did you use?: Pertronix Ignitor I or II? Mallory? Were the ballast resistors retained or discarded? Could the wrong kits have been installed ( but sounds like your timing advance may be good, depending on initial timing setting. )
Was this problem there before installing the kits?
Have mufflers been replaced with more restrictive ones?
Any chance the tachs are on the wrong pulse switch setting?
If you know for sure throttle plates open all the way with the controls,, and all cylinders are firing when they should and fuel quality is high, you might try having someone else run the boat at high throttle setting( >3000++ RPM while you slowly rotate each way the loosened distributor of one engine to see if there is any obvious improvement at full advance. But if so, I'd advise retarding total timing "a bit" to help avoid damaging future knock-detonation . Note, the Crusader factory techs do not recommend this, recommend only setting initial base timing. With your conversion kit I believe this will still rely on lubricated centrifugal mechanical advance with proper springs.
FWIW- The owner's manual I still have from my old 1988 Crusaders specs min. 89 octane for either engine.(-Is your fuel fresh or old/stale?)
And spec'd cranking compression of 130 p.s.i.
Initial timing : 10* BTDC ( Are you sure you are reading the timing notches correctly? Or are you using an advance light set to 10*BTDC and flashing on the 0* mark?)
In 1988 the lifters were hydraulic with no lash , ...and it doesn't mention preloading. No guess as to what the lash should be on yours, but you did mention 2 suspicious valves on each engine.
You are obviously experienced, so sorry for all of the above you already know and/or checked but sometime in the thick of it we overlook things until others may kick in our memory.
Phew, at least you should be able to get to sleep after reading all that! Best luck.
Both engines are now limited to ~3200 RPM, yes? And spec WOT RPM is 4200-4400, right? So it there might be some possibility 2 cylinders on each engine are not firing (correctly) *
Have they been limited that way ever since you have had the boat? How long?
When you advance the control throttle levers underway, do the engines reach 3200 at ~~3/4 of full lever travel, or not until the levers hit the WOT stop? [ Possible cable adjustment needed to fully open the throttle plates? Have control cables (or controls) been replaced without checking adjustment?]
Have you had the "20x23" props prop-scanned to see what you may really have on there now?
Are the props and hull quite clean or is there substantial fouling? Is the boat sitting lower relative to the painted w/l than it used to? ( compartments with excess retained water?)
Keep in mind , a 37' motorboat can get a LOT heavier due to many factors over 36 years and that alone could require even less prop pitch. And if by any chance by "350s" you mean the 350 c.i./270 hp Crusaders and not the 454 c.i./ 350hp engines, those would be under a lot of strain already to power that boat. 454 c.i.s , yes?
*Suggest trying attaching a timing light inductive pickup to successive plug wires to confirm each cable is carrying ignition pulse.That doesn't necessary mean those cylinders are firing , or at the right time.
*Have you triple-checked firing order for each engine? Plug cables all have continuity?
Standard LH rotation engine as viewed from flywheel end toward the pulley end: 1-8-4-3-6-5-7-2 .
Opposite RH rotation: 1-2-7-5-6-3-4-8 .
(Both LH & RH distributors turn CW.)
(DON'T judge engine rotation by prop shaft rotation, unless you know for sure the reduction gears do not have reverse output like mine have.)
What kind of distributor conversion kit did you use?: Pertronix Ignitor I or II? Mallory? Were the ballast resistors retained or discarded? Could the wrong kits have been installed ( but sounds like your timing advance may be good, depending on initial timing setting. )
Was this problem there before installing the kits?
Have mufflers been replaced with more restrictive ones?
Any chance the tachs are on the wrong pulse switch setting?
If you know for sure throttle plates open all the way with the controls,, and all cylinders are firing when they should and fuel quality is high, you might try having someone else run the boat at high throttle setting( >3000++ RPM while you slowly rotate each way the loosened distributor of one engine to see if there is any obvious improvement at full advance. But if so, I'd advise retarding total timing "a bit" to help avoid damaging future knock-detonation . Note, the Crusader factory techs do not recommend this, recommend only setting initial base timing. With your conversion kit I believe this will still rely on lubricated centrifugal mechanical advance with proper springs.
FWIW- The owner's manual I still have from my old 1988 Crusaders specs min. 89 octane for either engine.(-Is your fuel fresh or old/stale?)
And spec'd cranking compression of 130 p.s.i.
Initial timing : 10* BTDC ( Are you sure you are reading the timing notches correctly? Or are you using an advance light set to 10*BTDC and flashing on the 0* mark?)
In 1988 the lifters were hydraulic with no lash , ...and it doesn't mention preloading. No guess as to what the lash should be on yours, but you did mention 2 suspicious valves on each engine.
You are obviously experienced, so sorry for all of the above you already know and/or checked but sometime in the thick of it we overlook things until others may kick in our memory.
Phew, at least you should be able to get to sleep after reading all that! Best luck.
respond to Sandy, ignition was changed to Crane cams Xri mod. and yes max timing is 30 at 3000 rpm, bottom is clean , wires , coil and plugs are new and all cylinder's compression are all around 150 lbs . and tac's were checked with an digital tac. The only thing I did no mess with is the Quadra jets. and the engine is a 454 btw.
Charles- I hadn't heard of the CraneCams Xri conversion kit but looked it up. Interesting and looks easy. Nothing mentioned about a "marine " model like Pertronix and Mallory have , but I can't think of why this one would not work OK as it seems to. You did follow the advisement about checking for ballast resistor or resistor coil , right?
This certainly shouldn't be effecting your engine at 3200 rpm, but since the Crane conversion module has a setting for Rev Limiting ( 4000 to 8000?) hopefully the limiter rotary switch on the module is not turned all the way CCW to limit to 4000.
http://www.cranecams.com/uploads/instructions/9000-1700c_.
P. 4: http://www.cranecams.com/uploads/instructions/9000-1700c_.pdf
Re your valve lash note: CraneCams has a decent section dedicated to reason for and setting of hydraulic lifter pre-load on p. 354 here:
http://www.cranecams.com/uploads/catalog/Crane Cams Master Catalog.pdf
[ 1/2 to one full turn after 0 lash at the rockers w/ intake lifters at the top of the cam lobe to create 0.020-0.060" preload . Exhaust set to same preload but it explains when that is set relative to intake cam position. ( That's probably not stated well at all. )]
This certainly shouldn't be effecting your engine at 3200 rpm, but since the Crane conversion module has a setting for Rev Limiting ( 4000 to 8000?) hopefully the limiter rotary switch on the module is not turned all the way CCW to limit to 4000.
http://www.cranecams.com/uploads/instructions/9000-1700c_.
P. 4: http://www.cranecams.com/uploads/instructions/9000-1700c_.pdf
Re your valve lash note: CraneCams has a decent section dedicated to reason for and setting of hydraulic lifter pre-load on p. 354 here:
http://www.cranecams.com/uploads/catalog/Crane Cams Master Catalog.pdf
[ 1/2 to one full turn after 0 lash at the rockers w/ intake lifters at the top of the cam lobe to create 0.020-0.060" preload . Exhaust set to same preload but it explains when that is set relative to intake cam position. ( That's probably not stated well at all. )]