Venturing into performance upgrades for an AQ271C

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

Humpty Dumpty is going back together slowly

here are a few shots. spraying the flywheel and coupler, and the overall shot of today. need to grab the battery and hot-wire the coil, ad some fuel and fire it up

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

Its alive.......



video here of first startup:

http://rides.webshots.com/video/3002954950101989507frlsxt

used the multi-meter as my gauges for oil and temp. ran it enough to set timing and idle speed. now to finish the boat

 

[captmello]

Re: Venturing into performance upgrades for an AQ271C

Sounds great!

Would you mind recapping what you did to the motor? And, what HP gain do you think you've gotten.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

kept the short block in tact. I updated to vortec heads, switched to a vortec marine intake (factory Volvo Penta part). I added a carb spacer for low end torque. Added the Comp Cams 262/268 cam and roller rockers. added a Melling high volume oil pump.

Engine went from compression remains at 9.4:1 since the heads are still 64cc, however with the swirl chambers. Talking to the local engine shop, its estimated we bumped from 275hp stock to about 330-340 range.

 

[Tail_Gunner]

Re: Venturing into performance upgrades for an AQ271C

kept the short block in tact. I updated to vortec heads, switched to a vortec marine intake (factory Volvo Penta part). I added a carb spacer for low end torque. Added the Comp Cams 262/268 cam and roller rockers. added a Melling high volume oil pump.

Engine went from 9.4:1 to about 10.3. Talking to the local engine shop, its estimated we bumped from 275hp stock to about 330-340 range.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

just a few more pieces to bolt back into the boat and the engine goes back in.

 

[mybadford]

Re: Venturing into performance upgrades for an AQ271C

added a Melling high volume oil pump.

I like your set up and it sounds good too. Do you run thru hull exhaust?
Do marine engines not have high volume oil pumps in them? My AQ231A holds 80psi cold and 70psi warmed up at an idle. It buries the gauge anything beyond that. I thought the gauge might have been messed up but I put a mechanical gauge on it just to verify.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

no, the stock marine motor oil pump is the same as a stock truck motor.

I will eventually be running a thru-hull

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

Motor in, outdrive on.......its raining.........tach doesnt work...... troubleshooting in the rain is a pain in the backside.

 

[mybadford]

Re: Venturing into performance upgrades for an AQ271C

I was just looking for this thread wondering if you had the engine in.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

who ever designed the trapezoidal connector on VP wiring harnesses should be forced to listen to its a small world

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

after a few trips out, now time for carb tuning.



looks like I can go just a bit richer on the jets.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

Ok, its been about 15 months since I have put the boat back together. I think I need more power. It goes plenty fast, and burns plenty fuel, however I think it could go faster.

 

[Walt T]

Re: Venturing into performance upgrades for an AQ271C

I built a 383 stroker motor for my 22' Cuddy with 290 DP, boy oh boy its like a big block in there. On plane time and top speed all improved. Went up a pitch, its pretty sweet. I used flat top pistons with the stroker kit and its at 9.71 compression now with standard 76cc heads. This winter a set of Vortec 64cc heads will go on and intake of course with a cam change. I'll stay with the standard Holley 625 cfm I suppose. The change to Vortec should get me to 10.5 compression, but the math will tell. I read your thread with interest, seems we both like playing with motors. I've built several stroker motors for friends and each time they have been astounded by the torque improvement. These are built for torque, not HP.

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

Walt, thanks for the kind words. you might be a bit more than 10.5 depending on the gaskets used. which puts both of us into the buying better fuel category.

Which props are you running? I have both B5's and B6's that I run currently depending on what we are doing (cruising or water sports) and which ones need to be re-done.

 

[Walt T]

Re: Venturing into performance upgrades for an AQ271C

I use 104 octane boost now just so I don't take any chances with detonation. I have total timing around 36 at 3500 rpm which seems to work well.

I have B-5s which were and still are great skiing and tubing props, the low end grunt and on plane time really show up with the stroker. The engine will overwhelm the props pretty easy, it went past 5000 rpm and I decided that was enough so I don't know what top speed is with those. It was 44 mph gps at 4800 rpm with 1.95 ratio on the stock motor. I am in Colorado so I'm dealing with altitude. The stroker went right past that and past 45 and I chickened out. I didn't build it to breathe past 5000. I stuck my F-6s on it and it went to 5300 rpm 53 mph and was still going up but I could see boat wakes coming so I backed off. That's enough of that. Cruising speed is up a few mph with the F-6s on Lake Powell and fuel economy, such as it is, seems about the same but I cant really tell and it's all guessing anyway. Its fun to goose it and you're probably like me, just like the feeling of power when you hit the throttle no matter what you're driving. I do have a pretty good oil leak out the plastic timing cover I guess the O ring type gasket around one of the bolts is damaged. Broken shift cable now so I'm off the water for now. My boat is smaller than your Cruisers but you should get a noticeable increase in low end grunt.

 

[Maclin]

Re: Venturing into performance upgrades for an AQ271C

Walt, I thought of your stroker install when I read Scott's latest, nice to see you back "over here" again :yo:

 

[Walt T]

Re: Venturing into performance upgrades for an AQ271C

Nice to be back, Thanks. Miss the old TBM forums. Was glad to see Maclin there

 

[Scott Danforth]

Re: Venturing into performance upgrades for an AQ271C

I'm running the stock 615cfm carb from the AQ271 with different jets and metering valve. I am running 93 pump gas and have the timing set at a base of 10 right now. That and a set of B6 props and I'm hitting just shy of an honest 50mph. not bad for my beast of a boat. I need to adjust timing a bit more, I think there are a few more ponies to be freed up.

so F6 props fit on the 290DP?

 

[Maclin]

Re: Venturing into performance upgrades for an AQ271C

Has to be C6's, probably a typo there.

You are getting some really good numbers Scott, I bet that would surprise someone like me in a smaller boat trying to keep up! I can get past 50mph with B7's but that last 3mph or so takes a few more seconds than I would like. The B5's work well for us as we mostly are loaded and towing, those tap out at 46mph or so.

Good job guys, I am vicariously bench racing alongside...