3 liter cowl mods

[kllr bee]

I have gotten many emails about modifying a 3 liter cowl. I am going to put it here to help all.
The top rear of the upper cowl is held on by 4 bolts. Remove these bolts and get 40 mm long stainless bolts(I got them at lowes). Then get some stiff water hose the bolts will go through and cut 4 of them to 7/8 of an inch(all the same length).



Next you want to take all of the foam from the inside of the cowl and drill 5 or 6- 1 and 1/2 inch holes in the top of the inner liner of the cowl.



If you have 250 XB or 300 Pro Max computers you can also modify the bottom cowls to get more air in(cannot work with stock 225 computers they will read lean condition and shut motor down to 2000 rpms to protect itself). To do this you will need to pick up 2 or 4 stainless 3/4 inch clam shell cable covers. drill 3- 3/8 inch holes in a tight triangle directly under the butterflies of the intake. Then silicone the clam shells facing forward over the 3 holes you made. For me this added more air than the upper cowl mod.





Richard

[1outlaw]

Richard i have the same TYPE of lower cowl vents on my 225 that runs 225 computers and never had a problem...She has 300hours on her now!!!

[kllr bee]

I did single vents on each side of my 99 225EFI and when runnig hard it would shut down to under 2000 after about 5 miles running. If I blocked them off she would run all day. Put a 250XB fuel computer on and never had that problem again.
Richard

[dswindall]

Richard

When you put the 250 computer on your 225 EFI did you make any other mod's?

Dewayne

[kllr bee]

I've done them all. Check the thread about modifying a 250XB in this section. Basicly the same motor except for porting in block.
Richard


Modified by kllr bee at 5:06 AM 1/4/2010

[EuropeanAM]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kllr bee &raquo;</TD></TR><TR><TD CLASS="quote">I've done them all. Check the thread about modifying a 250XB in this section.
Richard</TD></TR></TABLE>

To read about Richard's other mods, look here:

http://www.bbcboards.net...-mods

[2fastr1]

Richard,
I have a 250 XB. If I raise the upper rear of the cowl, and install the clam shells on the lower portion what type of performance change should I expect from this?

[kllr bee]

Bass and Walleye did the mod to the top cowl on an XB some time ago and picked up 1.5mph. At a cost of about 5 bucks that is well worth doing. I feel the lower cowl mod helps about the same but I did not try to get comparison numbers.
Richard

[2fastr1]

Sounds like an easy 1.5 mph. Thank you for replying.

[Jiggernaut]

Just curious, where do you find the stainless cable clam shell covers?

[Jiggernaut]

I found some, but not sure what size. Maybe the smaller of the four?

http://www.westmarine.com/weba...18836

[EuropeanAM]

We have a couple sizes on our "accessories" catalog:

http://www.boatingstore.com/us...shell vent&cat=827

[Tom1985]

just did mine today but the lakes are still a bit ice covered ... about 3 inches lol cant just chop that up so ill have to wait and see what happens in the spring time

[kllr bee]

I uesd 3/4 inch clam shells got them at a boat dealer. They are actually through hull cable covers. West Marine would be a good online company.

[Bassfishingfreak]

I just finished the cowl mod on my 225efi. That's going to put a lot more air under the cowl. Thanks for the info guys.

[2fastr1]

Took me a while to take the time to do the mods, but they are finished. Raised the cowl, and added two clam shells to the under side. I went to several boat dealers around Lake Texoma, and no one had 3/4", so I put two larger ones on instead. Taking her out tomorrow to test her out. I`ll post up my results. Thanks again for the great info!

[fishfarm]

I got a 2000 225 opti if i did the clam shell mod do you think it would be running lean

[fishfarm]

[kllr bee]

Not tried that yet. Just got a 300XS and it is going to have to be left alone til warranty expires.
Richard

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by fishfarm &raquo;</td></tr><tr><td class="quote">I got a 2000 225 opti if i did the clam shell mod do you think it would be running lean </td></tr></table>

You need to be very careful here. The Optimax engines run at a much leaner setting (as compared to a Carb or EFI engine). They're based on a "speed-density" direct fuel injection technology, and the PCM/ECM has no means of recognizing (nor compensating for) changes in AIR FLOW.

Would it bother an engine on a "normal" rig? "Probably not" (but remember.... if you proceed, and it does, you obviously "own" the success or failure).

On a substantially faster rig.... a well scooped cowling "could" result in a substantial airflow increase (and air pressure readings inside the cowling "in excess" of atmospheric pressure) due to a "ram effect".

The EFI engines run at a much "fatter" (or RICH) setting, and are far more forgiving.