| Author |
Message |
    
Dean Vizia
New member
Username: sgnt_pepper
Post Number: 1
Registered: 05-2008
| | Posted on Monday, May 05, 2008 - 08:11 am: | 
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Hi there I have a v8 volvo penta inboard engine with a 280 leg and just recently the engine will only put out 4000rpm when in gear but revs up to max perfectly when not in gear. The hull is clean and prop looks good any help would be greatly received.Thanks |
El Pescador
Senior Member
Username: el_pescador
Post Number: 3087
Registered: 02-2006
| | Posted on Monday, May 05, 2008 - 08:16 pm: |
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A few questions:
What were the original "max" RPM?
Is the boat waterlogged in the foam compartments or have you added weight?
Are the fuel filter in the carb, the flame arrestor, and the anti-syphon valve clean?
Is the fuel in good condition?
Are all the spark plugs/wires/rotor & cap in good condition?
Is the ignition timing advance correct? |
Mike
Advanced Member
Username: mike77cj
Post Number: 123
Registered: 06-2007
| | Posted on Monday, May 05, 2008 - 09:33 pm: |
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I keep reading in posts that people are revving their engines to 'max' rpm with the boat out of gear. I have never thought it good to do this. In my opinion, the engine uses the 'load' as a means of balancing. When out of gear I limit revving my engine to 2500 rpm or less.
What's your thought on this one El? |
El Pescador
Senior Member
Username: el_pescador
Post Number: 3096
Registered: 02-2006
| | Posted on Monday, May 05, 2008 - 10:29 pm: |
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Mike, one of the dangers I see with revving-up an engine without load is that it is very easy to go overboard and damage can occur if the piston hits the valves due to very high RPM. The springs can make the valves retract only so fast. |
Dean
New member
Username: sgnt_pepper
Post Number: 2
Registered: 05-2008
| | Posted on Wednesday, May 07, 2008 - 10:25 am: |
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hi thanks for the offers of help the boat has not increased in weight the fuel is fresh will
check the carb again although I have cleaned it out already. I haven't cleaned the plugs or looked into anything electrical yet I didn't think this would be the problem if it ran up up ok out of gear. |
Dean
New member
Username: sgnt_pepper
Post Number: 3
Registered: 05-2008
| | Posted on Thursday, May 15, 2008 - 09:15 am: |
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Hi me again just looking for some more engine advice regarding my low loaded revs. I have changed the spark plugs, fuel water separater filter, checked the compression and cleaned out the carb. The engine is a 5.7GL is there a fuel filter in the carb or in the bowl where the fuel line connects to the engine, also just wandered if anyone could tell me what the screws on the front and back of the top of the carb are for I thought they were fuel adjustment settings and if so how do you go about setting them and could anyone tell me where the flame arrestor is. |
Hy Stat
Advanced Member
Username: hystat
Post Number: 287
Registered: 05-2007
| | Posted on Thursday, May 15, 2008 - 10:43 am: |
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an engine missing half its pistons will rev up to maximum rpm with no load. That test is meaningless and can very likely damage your engine. If you dont know basics like what a flame arrester is, I'm sorry but you need a mechanic- don't touch the screws on the carb. unless you want to have things really screwed up. |
Dean
Member
Username: sgnt_pepper
Post Number: 4
Registered: 05-2008
| | Posted on Thursday, May 15, 2008 - 12:48 pm: |
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I know what a flame arrestor is i was just looking for some helpful info on it's location and how to go about cleaning it, the same goes for the screws I never mentioned at any point I was going to touch them I was simply looking for someone to answer my question for my own knowledge. I know full well an unloaded engine will rev up fine so instead of stating the obvious any helpful tips as to why the revs are low when loaded that i havent already done and mentioned in previous posts would be appreciated. |
El Pescador
Senior Member
Username: el_pescador
Post Number: 3148
Registered: 02-2006
| | Posted on Thursday, May 15, 2008 - 01:13 pm: |
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What year is your engine? And is your carb a 2 or a 4 barrel? Some 5.7GL came equipped with Holley 4 barrel carbs, and some came with the 2 barrel.
Here is an exploded view of a 2 barrel
http://www.volvopentastore.com/5_7GL_IMDA/dm/cart_id.657400424--category_id.3424 64--session_id.651463300--store_id.366--view_id.311912
and here is a 4-barrel
http://www.volvopentastore.com/5_7GL_PLKA/dm/cart_id.657400424--category_id.3424 62--session_id.651463300--store_id.366--view_id.312476
Whichever carb model you have, it should be covered in the 1992-03 Seloc repair manual.
Also, I have to agree with Hy Stat. No offense intended, but if you are asking such basic questions like the location of a carb flame arrestor or how to clean it, I strongly suggest that you need to do quite a bit of serious reading before even thinking on working on your engine's carb. The Seloc manual I mentioned would be a good start. |
Dean
Member
Username: sgnt_pepper
Post Number: 5
Registered: 05-2008
| | Posted on Thursday, May 22, 2008 - 08:01 am: |
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Hi El Pescador the carb is a 4 barrel and after closer invest the 2 ports that should be opening at higher rpm to allow a greater amount of air into the mix aren't opening. Does anyone know if they are set mechanically to the throttle linkage or by some other mean. I ask this question as there is a slotted link connected to the trottle but also another little linkage the other side of the carb going up into a little chamber and I am unsure of this chamber's function. |
El Pescador
Senior Member
Username: el_pescador
Post Number: 3197
Registered: 02-2006
| | Posted on Thursday, May 22, 2008 - 07:56 pm: |
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If the carb you have is the one in the lower link on my previous post, the secondaries are vacuum actuated (see part 6 on the link).
This is the typical 4150 carb (yours, I presume):
http://www.holley.com/data/TechService/Technical/4150-4160%20Exploded%20View.pdf
These are instructions on hot to tune it:
http://www.holley.com/data/TechService/Technical/Carburetor%20Tech%20Info.pdf
Here are more links:
http://www.holley.com/TechService/Library.asp
The Seloc manual covers the description, overhaul and adjustment of your carb. You may be able to find some more info from the Holley site. |
Dean
Member
Username: sgnt_pepper
Post Number: 6
Registered: 05-2008
| | Posted on Tuesday, May 27, 2008 - 10:43 am: |
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Thanks for the info El Pescador it was a great help I have serviced the vacuum and it now operates alot better and am getting about 4500 rpm at max rev although the engine gets to this at about 3 quarter throttle and nothing happens in the last part of throttle movement. I am considering adjusting the float pins slightly to see if more fuel helps but am concerned that this could cause flooding at lower revs or have I missed anything else that can be tried |
