loss of power, increase in RPM

[Ciera2450]

Re: loss of power, increase in RPM

Thanks all! I was replying to one post the same time you guys were posting. This is a pain trying to sort out what someone else "modified"...

 

[captmello]

Re: loss of power, increase in RPM

check into this also. This is an electronic dist for the same money
http://www.marine-ignition.com/imdist8v.htm

 

[Ciera2450]

Re: loss of power, increase in RPM

Thanks for the link tailgunner! How would I address the coil if I replaced back to stock? This automotive dist. has the coil mounted on the cap..

 

[Ciera2450]

Re: loss of power, increase in RPM

Even better captmello! I may just order that and replace it all. Thanks!

Someone has done a hackjob on this engine and the entire boat prior to my owning it. I purposly omitted pics of the carburator. Its automotive also and the throttle linkage is all rigged up with homemade brackets. The carb will be replaced this offseason. If the admiral lets me spend the money

I will say tho...the boat has run like a champ the two years i've had it. Even with incorrect parts.

 

[Tail_Gunner]

Re: loss of power, increase in RPM

http://forums.iboats.com/showthread.php?t=489940

You will need this

 

[captmello]

Re: loss of power, increase in RPM

Even better captmello! I may just order that and replace it all. Thanks!

Someone has done a hackjob on this engine and the entire boat prior to my owning it. I purposly omitted pics of the carburator. Its automotive also and the throttle linkage is all rigged up with homemade brackets. The carb will be replaced this offseason. If the admiral lets me spend the money

I will say tho...the boat has run like a champ the two years i've had it. Even with incorrect parts.

Ya, that price for the EST Dist is almost to good! I haven't bought from those guys, but saved that link posted a while back. I'm still running the oem points dist. in my boat but if I needed to, I'd go with the EST instead of an electronic conversion kit.

If I were in your situation I would try to get the boat timed and running properly with the existing dist. since it ran good before. I hate throwing parts at a problem. Maybe check youtube for timing instructions...

 

[Ciera2450]

Re: loss of power, increase in RPM

Thanks for that link Tail Gunner!

 

[Ciera2450]

Re: loss of power, increase in RPM

I'm going to do that Captmello. I'm really thinking the distributor turned slightly and the timing was off. I'm going to check the timing tonight and see how it runs on the muffs.

 

[Ciera2450]

Re: loss of power, increase in RPM

Ok.....the mystery deepens...
I cleaned up the existing dist. cap and rotor and reinstalled everything. I found a few things....
1. the distributor hold down bolt was finger tight!
2. all the plugs have spark going to them
3. I aligned the distributor to an old photo I had showing its position (glad i had that). I also did the TDC on #1 and they appeared to be just about the same spot.
Well, the engine seems to run smoothly on the muffs. I ran up the rpm's to about 3500 a few times to test things out and it reved up fine. I have a buddy coming with a timing light to set it properly, hopefully tonight.

I'm thinking that the timing got thrown off by the loose distributor bolt.(hoping its that easy!) The orginal symptom started and then I changed plugs and the symptoms got worse. I may have moved the distributor pulling on the wires when changing the plugs....

But, just because it runs on the muffs doesn't mean it won't sputter and backfire under load. I'm hoping to get to the lake friday and test things out.
If it happens that the engine still has sputter and backfires under load, won't I be searching a fuel/carb issue then??? Or still an ignition issue?

 

[bruceb58]

Re: loss of power, increase in RPM

You are using a timing light to set the timing right?

 

[Ciera2450]

Re: loss of power, increase in RPM

Yes, I am waiting for my friend to show up with his light to properly set the timing.

 

[SteveMcD]

Re: loss of power, increase in RPM

Anyone that would put an automotive distributor and carburetor in a boat probably wouldn't think twice about the starter and alternator either. Tell the Admiral if we don't replace these things with marine rated, we could explode.

 

[Ciera2450]

Re: loss of power, increase in RPM

surprisingly steveMCD, the alternator and starter ARE both marine components. So far I've discovered the distributor and carb to be the only things NOT marine rated. Some PO has done a hackjob on this boat and i'm slowly getting things back in order.
(i won't even mention some of the horrific wiring i've run across or the merc. manifolds n risers on my volvo engine)

I still haven't had a chance to get ahold of a timing light to properly set the timing, I hope to today. I can't go boating

 

[Ciera2450]

Re: loss of power, increase in RPM

btw, that is a rather convincing argument i could present the admiral!!!

"honey, I need a $3,000 marine air/heat system and a $5,000 generator or we could explode!"

"honey, I need a brand spanking new 383stroker or we could explode!"

I think i'll use that one! (for the new carburator for sure!)

 

[Ciera2450]

Re: loss of power, increase in RPM

This is getting to be a pain......
I am still having the same issue. The engine seems to run normal at 800-1800 or so rpms. As I increase throttle the motor starts chugging and making a knocking sound that sounds like its coming from the port side valve cover toward the front. (but its hard to tell)
The knock and chug gets so bad that I HAVE to back off throttle for fear of breaking things worse. I attempted to rev the motor in neutral and can get the rpms to about 3500 before the motor makes some similar (not as pronounced) noises and i back off.

So far I have:
replaced plugs and plug wires
replaced dist. cap
replaced all fuel filters and fuel lines
removed and cleaned carburator
Oil pressure and temperature are normal
checked coil resistance (primary and secondary) and get normal readings

I have been researching my issue and am wondering if the timing advance may not be working properly. What do you guys think?
I'm trying to get my friend with the timing light to come by so we can check the timing advance. I'll admit, i didn't check this when setting the timing the first go around. I have removed the valve covers and the thermostat housing begninning to tear the motor apart to see what I find..... I figured before I go to far I'd get some advice.

Frustration is setting in trying to diagnose what is wrong with my motor....

 

[captmello]

Re: loss of power, increase in RPM

Sorry to hear it's still not working right. But, it's not time to tear the engine apart yet. Checking the timing advance is a good next step, since you haven't checked it yet. One step at a time.

 

[Ciera2450]

Re: loss of power, increase in RPM

Thanks for the reply captmello

with the automotive distributor thats in there, there is what I believe to be a vacuum advance but its not hooked up to anything and is capped off. It has never been hooked up.
Is there something else that would control timing advance?

 

[Don S]

Re: loss of power, increase in RPM

Check the firing order of your plug wires. Sounds a lot like you have a couple crossed.

 

[bruceb58]

Re: loss of power, increase in RPM

You still haven't checked timing? If you still have that automotive distributor in there, you won't get proper advance.

I also agree with Don that you need to check your plug wire order.

 

[Ciera2450]

Re: loss of power, increase in RPM

Thanks guys!
I'm pretty sure the plug wire order is correct. The problem began before I touched the plugs or wires and when I replaced them, attempting to diagnose the problem, I did one at a time to avoid confusion.
I WILL confirm the wire order to be sure.
As for the timing, I set 8deg. BTDC and did NOT check the advance timing. Which if my thinking is correct(and as bruce58 stated) the automotive dist. uses a vacuum advance that isn't even hooked up and has never been since i've owned the boat. Its very likely then that the timing advance isn't my problem....right?
Either way the distributor needs to be replaced with a marine rated one, so I'm ordering the delco est distributor system at the link posted by captmello.


Upon removing the valve covers, I notice that some of the rockers seem to "rock" more than others when wiggling by hand. One of them seemed awfully loose. Also, two of the valves DO NOT move at all, while all the rest "wiggle" slightly when moved laterally by hand.
I have NEVER torn into the top end of a sbc and i'm not really sure what is normal and whats not. Nothing appeared broken beneath the valve covers and there were no signs of metal shavings or anything. I suppose thats a good thing.

Something is making a racket inside the motor and it doesn't sound good!

I'd like to perform a compression check today and see what numbers I get. Do the autoparts stores rent or loan the equipment to check compression? Edit: i called oreillys and am heading there to purchase the compression tester. $30


Thanks for all the help and replies guys! I hope to figure this out with your help!
I realize the automotive carburetor and distributor complicate things and are a huge safety concern in a boat, but it ran normal with this set up and before i dump money to replace these things, I want to determine if the motor is worth spending the money.