triple 2.5 Merc (carbed) questions

[007joe]

Hello all!
I have a 32' Predator, with 3-2.5 liter carburetor-ed Mercs. I have a couple of issues, any help would be appreciated.
1. Fuel delivery- there are two tanks leading to a fuel distribution block, the motors each have an electric fuel pump, after the separator, once in a while after fueling up or running low on gas I will lose prime in the pumps and cannot get fuel up to the motors without a long intensive, gas drinking, siphon ritual. Has this happened to anybody? Is this a bad setup? I was thinking of installing 2 heavy duty, high flow pumps earlier in the fuel system to prime the smaller pumps, any thoughts?
2. They hate idling, I mean really hate idling, usually when I'm in a current with a crosswind, you would think I had crash boxes if you heard or saw this happening. What can I do to make them behave a little better?
3. The center motor seems to power the boat more than the outside two. Once on plane the center stick almost seems to control the speed of the boat with the outside two just helping move her along. I am bringing the props to a shop next week to get the hubs checked, but any other ideas would be great!
Thank you!

[quicklt1]

you should reach out to these guys..
https://www.facebook.com/pages/Water...98557123619603

[007joe]

Damn, their boat's together!

[Davidlake]

Contact "Davidmercury on "OffShoreOnly" He has a 36 Skater with four 2.5 Mercs. I am sure that he can lend some advice.

[quicklt1]

32 predator i believe is a vee ??

[007joe]

Yes it's a vee... I'll try OSO also, i think I've seen his project

[tux974]

Contact Mario @ 631 226 9617 He is on LI, has lots of knowledge with carb 2.5 motors and raced a 4-2.5 Mercs cat for years.

[donmac]

do the tanks have a crossover line to keep them equal level? is the fuel block higher than the tanks or is it part of the cross over? are there anti siphon valves on the tank pickups?are the lines from the fuel block to the fuel pumps equipped with check valves or do the pumps have checks internal? running low psi pumps or pumps with external regulator?what is fuel pressure to each engine?do they idle ok in neutral?with all 3 engines idling in gear and boat moving,what rpm will each one pull when throttle advanced fully on it?what rpm will each engine pull at max. speed
multi's have a lot going on when fuel for each engine is integrated with another engine!all the above questions I would ask myself if I was trying to figure out the fuel problem and engine equal loading issue[the center engine will always be doing more work, the prop is in the most efficient location]

[007joe]

No crossover
The Block is at the same level as the tanks (approximately)
No anti-siphon valves
No check valves
low psi pumps with no regulator
approx 7 psi
Idle okay in neutral, but not great
Haven't opened it up....

[2jz]

Hey adding check valves on each line after distribution block well help prime issues. When trying to prime system pump will pull from path of less resistance which is not the tank but other fueling line hooked up to block. As far as adding extra I think you asking for trouble shooting headache later on. Let say three supply go out your two primary high flow pump will still feed motor fuel maybe causing engine to fail and would add another restriction in fuel system adding more pumps.

[Turborr]

I have a setup something like yours. Only thing I can add is when I prime with the primer balls I have to squeeze two of them at the same time to get them primed and hard. If I try to squeeze one at a time it just seems like they never get hard.

lol....never get hard.

[tux974]

Ever think of running a small slosh tank, having a 7lb Holley to pressurize it from your tanks and then run your motor feeds from it.
This is how twin was setup and never an issue with fuel delivery. I'm sure the trips would work. The small lines to the top were for the EFI returns and were removed and capped when swapped to carbs.

[jdewaard]

Ever think of running a small slosh tank, having a 7lb Holley to pressurize it from your tanks and then run your motor feeds from it.
This is how twin was setup and never an issue with fuel delivery. I'm sure the trips would work. The small lines to the top were for the EFI returns and were removed and capped when swapped to carbs.

Nice setup Tony!!!! You always do such nice work. Functional and artistic at the same time.

[johnmiffco]

what carbed motors do u have
2.5 200s
or 2.5 245 style or ported motors
what carbs
holley reds flow 97gph
and if tanks have 2 - 3/8 hoses to a distribution block
there is not enough volume coming from the tank to run 3 reds
if have 1/2 or 5/8 pick ups and hoses from tank ur good
as stated the pumps pulling off a dist block with no ck valves is an issue
may need the purge tank when tieing all together
also shortest hose will get most suction to prime from tank,,,other line will aerate
I just converted a boat from twins to 3 carbureted motors
they are 260 ported pro max 225 s with racing wh-46 carbs
260 electronics,tuners and offshore housings

have 2 - 5/8 pick ups in tank
used a 140gph bypass pump to center motor
with regulator on motor
a 280 bypass pump on 2 outside motors
with regulators on motor
the bypasses are built into the pumps with a return hose to tank
from each pump
a bypass set up gives consistant fuel pressure
and harder suction to prime
having the pick ups separate has no priming problems

the center motor is the workhorse motor
with trips on a vee bottom
as it gets less slippage than the outside motors
the center motor prop is worked different than the outside props
I run 3 blade 28 cleavers on outside motors
a 4 blade 28 cleaver on center smaller diameter
this keeps rpms the same
but amazing control at high speeds and turns

the idling problem is just tuning
as a carb motor will idle all day long when clean and jetted propely

[Cp]

Nice setup Tony!!!! You always do such nice work. Functional and artistic at the same time.

Agreed. That is craftsmanship.