Looper advice needed

[Captain75]

After all the mods I've done to my 2.7 Looper (described in "Looper exhaust porting"), I got a BIG power increase, feels like a different motor.
Despite all this I'm not fully satisfied with the imediate throttle response off idle. I want a more crisp and rapid response.


Before I started the porting thread I drove an 175xflow with some intake mods and reeds on the same boat. Boat is alot faster with this modded 2.7 looper, but The xflow was stronger just off idle, in the beginning of take off?! How is this possible?
The xflow had no problem pulling hard out of the hole with a 22raker... My looper dont like pulling the same raker out of the hole at all!
I'm trying to understand how this is possible, and how to make my looper respond more crisp and be able to pull the same prop out of the hole without bogging and blubbering.
Once I finally get the looper to plane with the raker, its alot faster on top than it was with the xflow.


I went down from the 22"raker to a heavily cupped 19" aluprop, now the boat jumps on plane althought with a lower top end speed. Top rpm with the current prop is about 6100( with some trim left) Even though it jumps on plane you can notice a slight hesitation when you put the gear in and bury the throttle.


Boat is quite heavy, appx 2200lbs.


Question 1:
How is it possible that the xflow seems stronger off idle, when throttled up?
Question 2:
How can I get the looper to respond more rapidly and hopefully be able to pull my 22"raker hard?
Ignition advance is stock 18deg at full load.
Main jet is 65D, midrange is 14, idle is 48. (Pullovers were removed, became too rich) stock steel reeds.​ Midbore carbs.
I have another flywheel which is being lightened in the lathe machine, hopefully that will add some help to this problem.
Question 3:
My looper dont start with the butterflies all closed, I must use fast idle lever!? How do I cure this? Richer idle jets?


Hope you guys have some ideas!

[Captain75]

TTT

[Lockjaw]

When you ported it did you raise the compression?

I had a GT175 that had intake filler blocks, boyesen reeds, and 235 heads on a boat, and it was a stout running motor. It was a 93 octane only motor though. I put a stock 200 Venom on the boat when the 175 lunched a piston, and while it was faster, it wasn't quite as strong down low.

The 200 always was a cold natured motor too. Hard to start initially, once you got it cranked and running though, it started easily the rest of the day. I do not know what the solution is to make a 90 degree looper cold start well. My 60 degree looper 150 cranks up much easier when cold.

I'd be looking at putting reeds in your motor at minimum, and perhaps raising the compression, just be sure you have it jetted and timed properly before laying the wood to it.

[perfmarine1]

Do you have the exhaust opened up above the gearcase? Question 3 are you referring to hot or cold motor. Also I would try a trophy plus with small hub and vent holes, will spin up quicker since your boat is too heavy to run a overhub prop. Works great on my 20' heavy bass boat with a 150 merc in a 24 pitch.

[racer]

You have more weight on the back of the boat as well. Sounds like you need to work on idle jetting or amount of ventalation the prop has.

[mn808gade]

turn key on,push key in and then squeeze the primer bulb and keep pressure on till enough fuel is injected to make starting easier(before motor is turned over with starter).make sure fuel is being injected thru brass nozzles and primer is working.replace 3--4 primers a year Piston will not move inside primer( 3/8 reemer).-th

[phil blomquist]

Al has the ticket on the prop venting ! i had this very problem out of the hole too much power and not enough bite! went to a vented through hub and helped. Also wonder if it would help if you had some form of cavitation plate or drag plate for hole shot!

[Captain75]

Hello friends, thanks for your input!
Here are some answers;

Lockjaw;
I haven't raised the compression during porting, just brought it back where its supposed to be...
My plan is to send another set of cages to CCMS to have them cut and add glass reeds. I have a set at home, but I can't get them lapped properly. I will contact Mr Carson soon to find out if this is something he could do for me, including some info on prices.

6Killer;
Good advice!, any possibility to use the adjustable airjets for the later OMC carbs?

Perfmarine;
I thrashed my gearcase on a rock i july, that one had two 10mm holes facing downwards above the cavplate(like the Talon-mod), and two 10mm holes below cavplate, facing backwards.
The case I am currently using, has only got the holes below the plate. I can't tell a difference between the two cases apart from sound...
Motor won't start without the fast idle lever either cold or warm. When warm it ignites, but dies.
Last summer I had these relif holes made and threaded, didn't feel like it made any difference, just made everything black out of soot. Shall I open them up again?


Racer;
Does the idle circuit affect the take off?
My raker prop has got 10mm vent holes behind the blades.
Onces the blubbering stops and it comes on plane it "explodes loose" and I have to back the throttle fast to lower rpm and get grip.

Phil;
I have a large cavplate called Permatrim( NZ made)

hope this could spread some light...
//Anders

[hydrostream1]

Install fuel injection ,I have it on mine ,throttle response is incredible,raise the compression ,since it was ported ,you will lose bottom end,so you need to raise it to get the low end back.Yamaha ignition will help also.

[Lockjaw]

I would work with Al (Racer) on how to safely raise your compression, get it jetted properly, and the timing right. I never messed with my 200, but every OMC motor I have installed glass reeds in had better performance. I have only used boyesen reeds though.

[Captain75]

Install fuel injection ,I have it on mine ,throttle response is incredible,raise the compression ,since it was ported ,you will lose bottom end,so you need to raise it to get the low end back.Yamaha ignition will help also.

Yes its ported, howerver no duration changes or changes in blow down.
all ports are matched to the block and then polished. Exhaust ports have been widened in the upper part tapered down to stock.
My plan is to machine the heads to xp specs 0.675, instead of 0.700.
Motor has got fingerports added.

Portmap...

[Captain75]

I would work with Al (Racer) on how to safely raise your compression, get it jetted properly, and the timing right. I never messed with my 200, but every OMC motor I have installed glass reeds in had better performance. I have only used boyesen reeds though.

I had my fingers crossed hopeing he would reply. I'm very glad he saw this thread and, despite the amount of questions he recieves on this board all the time, took his time to answer - thanks Al!

[Captain75]

This summer my sons got their first boat, seems they already stuck on the speed on water area...
3,2m long, 15hp, almost 30mph...wish I was in their clothes
Lukas and Jakob, 12 and 10 years old.

[Captain75]

To the top...

[Captain75]

I managed to get a couple of hours of testing today.
I started by removing the 19", cupped aluprop(turning point Hustler) and put the 22" vented Raker back on. The Raker must weigh at least 10 times the aluprop...

First;
I tried stock orfices on idle and mid(48/14) and 65D in the mains( due to porting)
Result; Some blubbering when throttled up, once on the mains -buuhh
No airbox.

Second;
Made the idle richer, 39 instead of 48, airbox back on.
Result; Less blubbering when throttled up, pulls hard on the mains. Needed to open the butterflies with the throttle stop, just a tiny bit to make it idle. Recorded highest topspeed for the summer and therfore made my goal after porting and rebuild; 50,5 knots!(58mph). Tach only showed around 5500, so there must be alot left.
During this test I noticed that the motor surged for fuel at wot, rpms coming and going, perhaps its time to once again loose the VRO, or back it up with an electric inline.
Plugs and insulators light brown, when cut at Wot.

Third;
Same as above but 106 pullovers added.
Result felt about the same, plugs became dark brown when cut at wot.

Forth;
Aluprop back on. Pullovers removed. Airbox off.
Great response until it got on the mains, buuh, clearly way to lean.

Next step is to get the airbox back on and lean out the mid ( replace #14 with #26)to se if that could give me "dirtbike throttle response I am searching for.

Conclusion;
I have a feeling its easier to get this thing pull hard through the low and mid part of the rpm range by using both idle and part of the mid circuit at idle(butterflies tiny bit open)??!!

Reaching over 50knots was a big thing for me, mainly because my hull don't like that kind of speed. I can fly the bow up to about 40knots, thereafter boat starts to ride on its nose...
This winters project is adding a jackplate with 6" setback, and some speedrails to be able to fly the bow better.

I would like more inputs and ideas on jetting!