Mercruiser high RPM Ignition miss

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Dixieboy

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Apr 20, 2010
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I have a 1996 Bayliner with carbed 350. I got the boat with block busted from freezing. I replaced the engine, heads and intake. This enigne runs fine except for starts missing anytime I try to exceed 4800 rpm. Is there a rev limiter or could I have a problem with the ignition/module. Cap, rotor, wires and wiring check good. It has a Thunderbolt Ignition. Any suggestions???????
 
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chriscraft31

Seaman Apprentice
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Apr 19, 2010
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Re: Mercruiser high RPM Ignition miss

at 4800 RPM's on a boat you are probably floating valves. You should max out at 4200 or so, if not you need a bigger prop.
 
PitchFork

PitchFork

Petty Officer 1st Class
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May 28, 2009
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Re: Mercruiser high RPM Ignition miss

My manual for 1994 includes specs for 5.7L Alpha MCM 350 Mag Alpha and MCM 5.7L Bravo and the max RPM is 4800 range from 4200 - 4800. You probably need to increase pitch on the prop.

From iBoats Prop Page:
"A pitch change can increase or decrease the RPM's and bring RPM's into the recommended range. A 2" increase in pitch (for example, from 21" to 23") typically results in a decrease of approximately 300-400 RPM. "
 
Fun Times

Fun Times

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Re: Mercruiser high RPM Ignition miss

Dixieboy said:
I have a 1996 Bayliner with carbed 350. I got the boat with block busted from freezing. I replaced the engine, heads and intake. This enigne runs fine except for starts missing anytime I try to exceed 4800 rpm. Is there a rev limiter or could I have a problem with the ignition/module. Cap, rotor, wires and wiring check good. It has a Thunderbolt Ignition. Any suggestions???????
Click to expand...
Well you always want to make sure your tune up parts are in good working order.:)

But Yes you do have a rev limiter set to go off right around 4850ish RPM's, And it would sound like a high speed miss when you hit the rev limiter.

You will need to upgrade your prop with either a new one like described in the above post, Or you could try to see if a prop repair shop could rework your old prop.;) Good luck with it.:)
 
D

Dixieboy

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Re: Mercruiser high RPM Ignition miss

Thanks for the response and the advise. You guys are great. I've got a higher ptich prop coming to try. I have 30 years of experience with the small block chevy in many automotive applications such as muscle cars. 4800 rpm is just getting started for this engine. Any 350 will go to 5,500 rpm with no problem with valve float unless the springs or lifters are bad for a short period of time. I know a marine application is a little different and without the rev limiter some nut will just run it at WOT all day long. Thanks again.
 
bomar76

bomar76

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Re: Mercruiser high RPM Ignition miss

You didn't give enough informatiom for anyone to say if you have a rev limiter or not.
Thunderbolt IV does not have in any way shape of form a rev limiter.
TB V does.

And if you plan on spinning a stock 350/5.7 5,500 RPM in a boat I hope you are really proficient at changing engines 'cause you will be doing a lot of it.
 
Bondo

Bondo

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Re: Mercruiser high RPM Ignition miss

And if you plan on spinning a stock 350/5.7 5,500 RPM in a boat I hope you are really proficient at changing engines 'cause you will be doing a lot of it.
Click to expand...

Ayuh,... Right up the with Buryin' the throttle in Neutral ain't it Bomar,..?? ;)

The Cam tends to run outta Power at 4800rpms,+ the drivelines like that # for a Limit...
That's why it's a popular WOT #...

Dixieboy,... Your 96, Should be the T-Bolt V, so it should have a rev limited,...
But,..
I believe it kicks in at 5200rpms...

I'd sooner think you're runnin' outta Gas,+ goin' Lean at top end....
Change the Fuel Filters, Check the plug's Color,+ the Carb...

Welcome Aboard,...
It seems you've figured out the 400pound/feet of Torque at 4800rpms, is much more Important to a boat than 500hp at 6000rpms...
Good Luck...
 
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