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  #21  
Old 06-10-2021, 02:29 PM
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Quote:
Originally Posted by chrislandy View Post
so it's just centrifugal advance? I've only worked on HEI & dizzyless boat engines, the 351 specifics predate my knowledge, plenty of road cars with std dizzys, but not marine.

if the RPM is steady and the timing is hunting, then you need to look at the mechanical advance mechanism - clean / rebuild / replace as needed. Looks like you've ordered a new dizzy so a moot point really.
One of the spring's is broken and new springs are not available. So instead of a 10 cent spring you have to buy a $350 distributor...
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  #22  
Old 06-10-2021, 02:48 PM
88 PS190 88 PS190 is offline
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Quote:
Originally Posted by chrislandy View Post
so it's just centrifugal advance? I've only worked on HEI & dizzyless boat engines, the 351 specifics predate my knowledge, plenty of road cars with std dizzys, but not marine.
If you think about vacuum advance and what they do - you'll realize why we don't use them in boats. The vacuum advance only works in portions bits of the engine's power band usually when the throttle is mostly closed like if you're going down a flat stretch of road.
You aren't revved up enough to get a lot of advance (mechanically) and you're not under much load so there's not much risk of pinging but the advance isn't high enough to make good power so you feel a dead spot.

But also the throttle plate is mostly closed so the manifold vacuum is high which pulls some extra advance. Floor the engine, the throttle opens the vacuum drops, the vacuum advance backs off and the mechanical advance increases as the RPM rises.

Since boats never coast and are never really run under light load they basically never can take advantage of any vacuum advance and there is no reason to let them have it.
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  #23  
Old 06-10-2021, 04:25 PM
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Quote:
Originally Posted by stuartmcnair View Post
One of the spring's is broken and new springs are not available. So instead of a 10 cent spring you have to buy a $350 distributor...
Inboard Online lists Distributor Springs for 351 (standard and HO)....I assume these would be corrrect? Inboard Online is Indmars online parts division.

https://inboardonline.com/springs-di...std-ho-755023/
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  #24  
Old 06-10-2021, 06:21 PM
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Quote:
Originally Posted by d2jp View Post
Inboard Online lists Distributor Springs for 351 (standard and HO)....I assume these would be corrrect? Inboard Online is Indmars online parts division.

https://inboardonline.com/springs-di...std-ho-755023/
Agree. Those will work and should be the application fit.

To the OP, make note of which spring came from which lobe. There are two different sizes.

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  #25  
Old 06-11-2021, 06:11 AM
chrislandy chrislandy is offline
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Quote:
Originally Posted by 88 PS190 View Post
If you think about vacuum advance and what they do - you'll realize why we don't use them in boats. The vacuum advance only works in portions bits of the engine's power band usually when the throttle is mostly closed like if you're going down a flat stretch of road.
You aren't revved up enough to get a lot of advance (mechanically) and you're not under much load so there's not much risk of pinging but the advance isn't high enough to make good power so you feel a dead spot.

But also the throttle plate is mostly closed so the manifold vacuum is high which pulls some extra advance. Floor the engine, the throttle opens the vacuum drops, the vacuum advance backs off and the mechanical advance increases as the RPM rises.

Since boats never coast and are never really run under light load they basically never can take advantage of any vacuum advance and there is no reason to let them have it.

Yeah, I thought about it after & it makes perfect sense, never gave it a second thought before -

So the boat essentially only uses a narrow range of load vs rpm so doesn't need to have the advance adjusted for load beyond one curve - although I would make the argument that in newer boats (wake/surf/crossover) you do have that difference in load to RPM, but then you have dizzyless ignition now so it just gets taken into account in the ignition map
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  #26  
Old 06-11-2021, 12:57 PM
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Quote:
Originally Posted by d2jp View Post
Inboard Online lists Distributor Springs for 351 (standard and HO)....I assume these would be corrrect? Inboard Online is Indmars online parts division.

https://inboardonline.com/springs-di...std-ho-755023/
So I was lied to by two different companies. Thank you so much for this! Ordered.
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  #27  
Old 06-11-2021, 04:41 PM
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Originally Posted by stuartmcnair View Post
So I was lied to by two different companies. Thank you so much for this! Ordered.
You're wecome. I hope they are part of the solution that get's you going.

I found them at Inboard Online AFTER I had ordered and installed a new Pertronix distributor

FWIW - Inboard Online is a great resource. It's not the easiest website to navigate but they have a lot of parts for these old engines and for the most part the prices are good. Between them and SKIDIM I think I can keep mine runing until I'm not running LOL.
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  #28  
Old 06-11-2021, 04:50 PM
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Originally Posted by d2jp View Post
You're wecome. I hope they are part of the solution that get's you going.

I found them at Inboard Online AFTER I had ordered and installed a new Pertronix distributor
You came out to the better.


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  #29  
Old 06-14-2021, 09:36 AM
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Still going to order a new one but hopefully can get this one through the summer.
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