1800rpm=nothing

[76 searay]

I have a 76 mercruiser ford 302 v8, It will start up, although sometime difficult and needs a jump. but once I get the rpms up to around 1800 in both neutral and gear she just knocks and then dies. I have done a complete tune up including cap, rotor, points, condensor, plugs, wires, fuel water seperator, battery cables, starter and the solenoid. I have set the timming to around 8deg. btdc. does anyone have any ideas for me, Thanks in advance. paul g.

 

[thumpar]

Re: 1800rpm=nothing

Mechanical advance OK? Does the fuel supply hold up? I am a basic troubleshooter and am sure others can offer more advice but at least you have some thing to check.

 

[76 searay]

Re: 1800rpm=nothing

i took apart my distributer and cleaned/lubricated. not sure how to test it though. things seemed ok. have not done a fuel pressure test yet but that may be a good starting point. could it have anything to do with either the shift interupter switch? the nutral safty switch? or the so called riesister which I can't locate. Thanks

 

[Bondo]

Re: 1800rpm=nothing

could it have anything to do with either the shift interupter switch? the nutral safty switch? or the so called riesister which I can't locate. Thanks

Nope....

What the motors Compression,..??

 

[76 searay]

Re: 1800rpm=nothing

the compression on all cylinders is 115 to 120, which seemed to be ok based on an older condition motor according to the seloc manual.

 

[76 searay]

Re: 1800rpm=nothing

I read in seloc that if i have a coroded wire at the resister this could allow for a drop in initial power as well as it not allowing full power to wot. I don't know were or if I have this resister. could it have been removed and if so would that be a bad thing or would that still allow the boat to run wot. I am going to replace the fuel line today as well as checking the vent line. any other thoughts to start off at. it just seems electrical since things start to brake up at these rpms and the motor starts to knock pretty hard then stall out. Thanks

 

[Bondo]

Re: 1800rpm=nothing

and the motor starts to knock pretty hard then stall out.

Ayuh,..... That doesn't sound very Electrical......

 

[76 searay]

Re: 1800rpm=nothing

does anyone no were i could find out about firing order or were the # one distributor wire should line up at. the seloc book does not show this I lined up the #1 with the number one cylinder. with a left hand rotation of 1-3-7-2-6-5-4-8. again she runs fantastic up to this 18-2000 mark and then just falls apart. Thanks

 

[Don S]

Re: 1800rpm=nothing

Here is the firing order. One thing you have to understand, #1 can and may be in a different location than that shown, it doesn't really matter where it's at, but you do need to know which one it is.
Bring #1 cylinder to TDC on the COMPRESSION stroke and line up the 0? mark and the timing pointer on the vibration dampner and look at where the rotor is pointing. That is #1 TDC

 

[76 searay]

Re: 1800rpm=nothing

thank you guys for the help so far I have found a couple of burnt ground wires and extra wires in the boat which lead no were at all. I working on fixing all this and cleaning all contacts and will update with results tonight. Thanks for the help so far and lookforward to any other advise. Thanks

 

[CharlieB]

Re: 1800rpm=nothing

How LONG does this motor run before it starts 'knocking'?

What temp is it?

Are you in the water or on the hose?

Is it circulating water?

Is there any OIL in this motor?

What is the oil pressure? Cold? Warm?

 

[76 searay]

Re: 1800rpm=nothing

I am using muffs in the yard.

water is circulating, I rebuilt the water pump this year.

the temp is just out of the cold red on my gauge and into the green.

it will idle and work up to the magic 1800 all day with no problems at all. no matter how long I run it.

I did do the 1 pint in 20sec test on the fuel and only had half that at best. so I have replaced all the fuel lines and am going to lookinto the pump tonight. I will update with new numbers tomorrow night. I think the knocking is just the motor shaking as it tries to stay alive and not stall. Thanks again for everyones advise I have faith we will get this solved soon. god no's im running out of parts to replace. Thanks...

 

[76 searay]

Re: 1800rpm=nothing

I forgot oil pressure is 40-50 cold-warm

vacuum is around 15-20

 

[76 searay]

Re: 1800rpm=nothing

fuel pump seemed fine should i switch to electric or stay mechanical?

 

[Bondo]

Re: 1800rpm=nothing

Ayuh,.....

If there's Nothing Wrong with the fuelpump,..... Why change it,..??

Going Electric will only mean More Work to do it Right.....

If by Chance the Fuelpump is Bad,... Replace it with a New 1 like the old 1....

 

[76 searay]

Re: 1800rpm=nothing

Well Im still up a river with out WOT! I have discovered by putting a timming light on each of the spark plug wires that when the motor brakes up at around 1800rpm that all the cylinders miss fire. So now I lean twords electrical. I no the dwell is at 28-30, the timming is at 10deg BTDC. Temp is in the normal range, the whole fuel system is new pump lines, tank, filters. The distributor is mechanical advance, but things seem free in there with a finger pushing the weight test. the carb is rebuilt. new cap, rotor, points, condenser, plugs, wires, new battery cables, new starter, new starter solenoid, not sure if it could still be the distributor, or the coil. could it have anything to do with the gauges up front? Please any steps to diagnose would help. Merc 302 1976 188hp. Thanks...

 

[Silvertip]

Re: 1800rpm=nothing

If you had the distributor out and worked on it I would suspect you have a timing or firing order issue. Are you sure you are on #1 plug wire when setting the timing.

 

[daydreamer1252]

Re: 1800rpm=nothing

Did this start happening after the replacement of points, condenser, etc. or was that the reason for the replacements? I have had similar symptoms with condenser failures in cars (years ago when they had condensers) both times a failed ground of the condenser. It causes the points to arc badly and will break up at higher RPM, idle is always perfect. One a failed spot weld from the bracket to the can and another worked loose. My suggestion if this happened after the "tune-up" would be to replace the condenser with the old one or another new one and see if it improves. Sure is inexpensive trouble shooting!! Good Luck.

 

[Silvertip]

Re: 1800rpm=nothing

If you bought a "cheapy" points set, that may also be an issue. I've had them where one of the contacts was not tight in the bracket. Worked ok at idle but the engine fell on its face at higher rpm. Don't continue to replace parts that you have no idea whether or not they are bad. That gets expensive. Diagnose first, then replace. Right now you are not sure whether the problem is fuel, electrical, mechanical, or timing.

 

[hard-3]

Re: 1800rpm=nothing

check the voltage at the coil and make sure it does not drop off after a few minutes. sometimes a defective coil will work at low rmps and spark voltage falls off dramaticly at higher rpm's . I had a jeep that ran at low rpms and idles great but would not accelerate , changed condensor , ran great.i'm not sure if your engine has it or not , but some cars have a resister built into the starter relay that drops the voltage to the ignition coil for running, seems like around 12 volts cranking and down around 7-8 running .I think it is to make breaker points last longer. check the ground wires for corrosion and good continuity. if the thing cools down and runs ok next time until it heats up it sounds like ingition breakdown to me. get one of those spark checkers and pull off a plug wire and run it while observing spark color, should be nice blue fire, if it's yellow look for cause of low voltage.be carefull of any fuel leaks while doing this. it will make a noticable miss ,but you will be able to see if coil breaskdown is trbl. Check out an automotive shop with an o-scope or vo-tech school that you could take to and run . an o-scope will tell all ignition problems ,primary and secondary circuts. good luck
Jeff