Common HP upgrades on Crossflow

[joezek]

I had to take my 140 looper out of service for a while unfortunately, and will really be missing the power. Probably for the rest of the summer I'm stuck with a 110 crossflow. I've heard there may be some minor mods I can do to help get similar performance to the 140. ...Well, what are they? Reeds, compression, anything else? I basically used my new ignition system off the 140 because this 110 was seriously butchered by an attempt by some hack to make it run, and it did NOT run. It had an older 115 dual powerpack setup, and wrong flywheel. Now it runs perfect but half as loud as the 140, there's no crackle, no feeling like it's gonna make any power when I get it in the water lol. Its on a 17 Mako, great matchup, but no more 50+ MPH fun like before. At least I'll save a little gas

 

[jimmbo]

Your 110(prop rated)hp is almost the old 140(crank rated) crossflow. Forcing anymore power out of the 99 cu. in. block will make it a chore and less than fun to drive. Doubt this engine is any better on fuel than your 140 looper

 

[emdsapmgr]

.You can squeeze extra hp out of that 110. 1. Install the rubber intake filler blocks from the early 140's. On a V4 they are worth 3-5 hp. See picture. You'll have to scrounge around as they have been NLA for years. 2. Get a set of high compression heads off a 79 140. Better still, get a set of heads off an early 135 (1973/74). Your engine currently has low compression (bathtub) heads. 3. The engine already has the bubble back exhaust! 4. I'd install a set of carbon fiber reeds. Wont see much top end improvement, but you will like the idling and midrange pickup.

 

[joezek]

Thanks for the info, I didn't realize about the crank vs prop ratings too. I thought evinrude just used the crank for all their ratings and Mercury used the prop, at least on the Older engines. I'll definitely be doing those mods

 

[willamettejeff]

FYI - Intake filler block P/N is 322684. You will need 4. I purchased mine on EBAY. Also, not mentioned was upgrading to larger carburetor throat size to match those on your 140 to maximize hp increase. This is specified on the front of the carb just below the throats. Not sure what you have now.

 

[willamettejeff]

Would also caution not to upgrade to composite reeds until motor is running fine with all other upgrades made. The composite reeds are not as forgiving as the metal ones to lean sneezing or backfires that may result in the course of other changes being made. I learned this the hard way when ended up with fuel delivery problem to new-to-me carbs not directly related to the changes that were made. It happens.

 

[jimmbo]

3 - 5 hp increase equals 1/2 - 1 mph. Bigger carbs will help the top end, but weaken the hole shot. the 1973 135 heads are harder to find ever since an article in a Jan 1998 magazine regarding hopping up the 99 in block. One other desirable part is the exhaust tuner from a 1977 140, good for 1/2 mph on a light boat

 

[flyingscott]

My opinion is just leave it alone save the money for your rebuild. All the mods are not cheap for maybe 3-5 MPH a lot of labor will be involved. You will also be doing a lot of experimenting with jets in the carbs. The experimenting alone will probably take longer than rebuilding your 140. I would just make sure your compression is good and you have good spark that should have a pretty good exhaust sound on the muffs. If you decide to mod it make sure you are starting with a healthy motor first. You can probably get similar results from optimizing your set-up.

 

[joezek]

I did go ahead and do some of the minor bolt on changes before installing the 110. I did the rubber intake spacers, 140 high compression heads, and the ignition system from my looper. The boat still has so much less power still than with the Looper, what a big difference. Before I could be cruising at half throttle, and if I pushed the throttle more you'd get pushed back in the boat from the acceleration. Now, there's no mid range or high end power. Actually, before the boat would almost completely launch itself out of the water like a jetski on the holeshot- now I have to wait about 8 seconds to get on a plane.......SUCKS. I had the boat almost to 56 mph with the Looper, lucky to get 37 mph out of it now. The only good part now is it idles much smoother and quieter which = happy wife....The boat no longer shakes at lower power settings.

 

[Chinewalker]

The big block 140 looper is a real torque monster - much better punch than the old crossflows.

Part of your issue could be prop selection, too - if your 110 isn't peaking in the 5500-6000 RPM range, you're lugging it and will need to go lower in pitch. Going lower in pitch will also help your acceleration.