high exhaust temp on 2.4L Mariner

[David Borg]

I have a 2.4L mariner 1982 block 200 hp

Boyesen 7 petal horizontal reeds
ported reed cages
bobs exhaust Tuner
wiseco pistons
WH 22 carbs
Carbs Velocity stacks
1989 ignition system with 40amp charging system (watercooled regulator)and flywheel

I have a dual exhaust pyrometer and when I go at wide open throttle the Temperture goes up to 1100deg from 5K onwards up to 6K and it slowly keeps going up .

I jetted and rejetted the high speed jets up to 90 ,
timing is at 22BTDC at Cranking
High speed advance is disconnected.
Fuel pressure is 2 psi.
Is it normal to have to jet these carbs so so high ??are these carbs any good for my engine as I heard that normally WH 15s are used on these?
The Spark plugs are very light brown color.
When I connected the High speed advance module the engine stopped at 5600 rpm ... at WOT .Could it be a tiiming prob , when a rebuilt the engine I timed it with the mark on the flywheel cover .
compression is 105 on all six.

can some one please help as I wouldn t like to melt a piston the engine only ran about 30 hours .
Should I keep rejetting till I get the temp right ?? or is it a problem with the ignition system ? :confused:
Thanks in advance

[MadTing]

Fuel pressure too low. Should be 4-5psi.

[150aintenuff]

the modual is a HIGHSPEED RETARD and idle advance thus that is why it falls off at 5600... TO me you sound either LEAN or your reading the flame kernal and are rich, what do yer piston tops look like, are they paperbag tan or ar they shiny metalic???

You MAY be overrich but to find out do a throttle CHOP and check the plugs AND piston tops to see if there are carbon build up OR if they are TOTALLY clean....
do some searching, jay smith and others have posted MANY times about jetting

get yer fuel pressure up and then you SHOULD be rich and temps chould come down if infact yu are Currently lean

[David Borg]

thanks for your replies, how can I identify if the module is a high speed advance or a high speed retard, wht Im sure is that I had ordered it from the local merc dealer.
will the high speed advance make a difference in top speed/top rpm??

The tops of the pistons look quite black with carbon build up .

I will see what to do with the fuel pressure as I had already installed a 5 psi electric pump but apperantly its not good enough all fuel lines are 3/8 Id and connections also.

[MadTing]

High speed advance only is for the 2.4. High speed advance / retard is for the 2.5. The 2.5 module will advance 6 deg between 5000 and 5600rpm, and retard 4 to 6 deg above 5600rpm.

If you are using either module, set cranking timing to no more than 20 deg.

[David Borg]

thanks Mad thing , which would be my best option high speed advance or high speed retard? what effect to top RPM?

[MadTing]

How much RPM are you looking to turn?

[David Borg]

At the moment the engine is turning 6000rpm at WOT with a 27pitch surface prop.
I would like to go for the maximum RPM possible for best top end

[MadTing]

I would suggest that you remove the module completely, and set max timing to 24deg.

[David Borg]

many thanks I will try that one for sure

[us1]

1100 is too cold not too hot. I run lake motors at 1150 to 1200 at WOT.

[David Borg]

:confused: Dear us1


many thanks for your reply ,

Now i am confused , I was told that 1050 should be the best temp to run the engine and 1100 is marginal as that is close to the melting point for the piston , is that wrong?? what would be the highest egt I should run the engine at without risking to melt a piston? the gauge's maximum reading is 1200 its a hewitt (if it makes a difference)

once again thanks

[us1]

Ideally 1150 to 1175 is great 1200 is where I run my lake boats but its closer to melt down. When I race I run 1250. They melt at 1275 to 1300. I would not run yours over 1200. Shoot for 1175 to be safe and have a long lasting motor. Keep in mind all gauges and probes will read differently You need to go by piston color and just use the gauge for monitoring. Never jet on a EGT gauge alone Jet by piston color and see where the gauge reads then just monitor the motor to make sure it keeps running at that temperature. If you are too rich you could also be reading the flame and getting extremely high and inaccurate measurement.

[David Borg]

Many thanks that made everything clear now :)