www.iFourWinns.com

Question for the experts on here. My Boat has never run at max RPM's at WOT. I had it tuned up and gained we found the tach was off 1000 rpms and the timing was way off. The boat runs much better now and idles smoother. I picked up almost 600 rpms and the tach is only off 300 rpms now. It still feels and sounds like the motor is not hitting max and doesn't have the power it should. I am at 4300 rpms now so I am getting closer. I was checking the carb out today and noticed it is a 2 barrel. The boat originally had a 5.0l and was replaced with a 350. They reused the 2 barrel carb. Could this be part of my power problem?

Thanks in advance and Happy 4th of July.

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Todd
1988 Four Winns Horizon 200
AKA "Summer School"

Well in my OMC owners manual...it lists the 5.0 and the 5.0 as both coming with the 4 bbl carb...but then in the shop manual it makes reference to the 5.0 also coming with the 2bbl....and the outdrive gear ratios are slightly different....1.50:1 for the 5 liter and 1.41:1 for the 5.7...but as far as gear ratios...you have the 5.0 ratio (unless that was changed too) with a 5.7 motor so it SHOULD be able to pull max rpms....
The one other thing I can tell you is for my engine...the 4.3, was available with the 2 bbl and the 4 bbl, both with the 1.68:1 ratio, mine has the 4 bbl Rochester Quadrajet.
the 2 bbl has a max rpm range of 4200-4600
the 4bbl has a max rpm range of 4400-4800
Now I tried mine with the 14 1/2 X 19 prop it came with and barely got 4200 depending on the trim..loading etc. I was looking around on the FW website and noticed that they had charts for the prop diameter/pitch adn speeds for different models....as turns out the 88-92 Horizons and Sundowners (20 footers) with the V-6 were supposed to get the 15 X 17 prop...not the 14 1/2 X 19 that the V-8 models came with...
Went to a 15 X 17 prop and it easily pulls 4800 now and jumps up on plane much faster...

Double check the timing (8* BTDC for premium gas) and point gap/dwell (gap=0.018; dwell 30* +-2*) remember that point gap and dwell are inversely proportional.. as your point gap gets bigger, the dwell angle gets smaller...my dwell was a little low (point gap too big) so first you set that...then you set the timing...set the base idle speed....then in the water...if you have an advance timing light where you can dial in the degrees of advance it should have at a certain rpm and check that ( think mine was about 32*total at 3000 rpm). The reason why I say check in the water is you shouldn't run an engine on the water hose at 3000 rpm! Getting my dwell & timing right...with the correct prop made all the difference....If you want to go with a 4bbl don't forget you have to change the whole intake manifold....I'd look at the points I mentioned and check your prop pitch...make sure that when you put the throttle at WOT the throttle plates in the carb are actually at WOT..

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Lou thanks for the reply. I agree on setting it in the water as the muffs are not good for high rpm. I guess it is time for me to start learning about timing myself. I had it set by the local OMC mechanic and it indeed picked up rpm's. That is a good point about the intake. I noticed that when I took the flame arrestor off and put the throttle at wot it did not full open up in the carb. I will check again with the engine running in the lake and see what it does.

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Todd
1988 Four Winns Horizon 200
AKA "Summer School"

Todd if you want to check the carb to make sure the throttle plate is opening all the way...no need to do it with the engine running...just remove the flame arrestor...and have someone put the throttle in the WOT position while you watch it...revving the motor to WOT with the flame arrestor off can be dangerous if it backfired (not likely but possible) it could cause a fire in the engine compartment...not what you would want with you looking down the carb!

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Lou when I checked it as you suggested it did not open all the way. How do you adjust the carb? I have a seloc manual to get me by until I find some service manuals, and it didn't say squat. Also noticed the flame arrestor was black around the outside from oil blow by. Is there any reason I should not put valve cover breathers on and eliminate that blow by?

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Todd
1988 Four Winns Horizon 200
AKA "Summer School"

I was wrong before the carb is opening correctly. I got some numbers and I wanted to see if you guys agree with me. I think my biggest issue is the tach is inaccurate. I got some gps speed numbers to help determine how the motor is running.

The lake I was on is at 3300 feet of elevation. I had a full tank, and 2 adults and 3 kids in the boat. Estimated weight of fuel and people and gear was an additional 980 pounds. I have a 14.25 X 19 four blade aluminum prop and hit 38 mph. The lake was smooth, but glass so I am sure I could get to 40 if it was flat. The rpm's were at 3300. The tach had been off by 1000 originally compared to the shop tach were the boat is worked on. They said they got it to with in 300. The boat got up on plane with out any problem. I still have not had a skier or wakeboarder behind the boat to see how much pull it has. I am thinking it is time for a new tach. What does everyone else think.

The specs for the boat from four winns can be seen at the below link

http://www.fourwinns.net/fastfacts/fast ... 0-13sb.pdf

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Todd
1988 Four Winns Horizon 200
AKA "Summer School"

Even if both the 5.0 and 5.7 engines had the same basic 2bbl carb, wouldn't the carbs have different main jets and possibly other jets/ air correction tubes etc to allow for the greater air throughput/ fuel requirement for the bigger engine? It's certainly the case with carbs on car engines.

Do the plugs look like they are running a weak mixture?

Graham

My bet is on the 4-blade prop being what is "holding you back."

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Paul
2007 Four Winns Horizon 220
Mercruiser 350 Mag MPI w/ Bravo III Drive
2004 Ford Explorer Limited (V8-AWD)
Pomme de Terre Lake (Southwest Missouri)

I think a 5.7 L --running at 4600 rpm would be pumping air where it needs a carb of about 650CFM -- does the 2 bbl flow 650 CFM --- there should be some data on the carb somewhere--- I am not sure a low CFM carb even rejetted will work

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DaleG -- West Palm Beach FL
2003 240Horizon -- 5.7Gi -Duoprop

Dale,

The Clymer manual I have ( which I don't use very often because I don't trust the data 100%!), gives some data on the Holley carbs fitted to the 5.0 and 5.7 engines:

R-75004A; 500 cfm 2v- 5.0GL and 5.7 GS ( same #69 main jet sizes maybe it's a misprint and it means a 5.0 GS if such an engine existed!)
80402: 500 cfm 2v- 5.7GL (#75 main jets)
80390: 650 cfm "spread bore" ( whatever that is; 4v?!)- 5.7GS ( #60 main jets)

The Ford derived 5.0 and 5.8 engines use different ones:
80382: 490 cfm 2v 5.0 (#72 main jets)
80383: 600 cfm 4V 5.8 (#67 main jets)

(you can tell it's a rainy afternoon here and a lousy week ahead as far as boating weather goes!)

Graham

Thanks for the ideas and help so far. The reason I have been looking into this is that the motor does not reach the rpm range it should. I have two issues I am suspecting. The first is the tach is not 100% accurate but I know it is still not in the operating range it should be. The second is the carb is for a 185 hp motor. I have all the numbers I could find on the carb and I have not found any flow data. The numbers on the carb are 61529x17, 17059060, 041 T81, and also says 2 jet on the front.

This is what I am thinking I need to do now. I need to get a new accurate tach so I no the rpm's I am running. Then I can start to look at the carb. How do I know what tach would be good? I know Iboats has a bunch on their web site.

I have 3 props.

The first I have not used is a 15X15 aluminum I am concerned about over propping the motor.
The second is 15X17 which I was able to achieve aprox 3600 rpms and aprox 34 mph at 3300 feet of elevation
The third is a 4 blade 14.25 X 19 aluminum prop which reached aprox 3300 rpms and 38 (gps verified) mph at 3300 feet of elevation

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Todd
1988 Four Winns Horizon 200
AKA "Summer School"

I'd be interested to see what you got out of a 19 with only 3 blades. I realize you don't have one, just saying that is my very non-expert take on this.

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Paul
2007 Four Winns Horizon 220
Mercruiser 350 Mag MPI w/ Bravo III Drive
2004 Ford Explorer Limited (V8-AWD)
Pomme de Terre Lake (Southwest Missouri)

At 3300 ft, wouldn't you have to drop pitch a bit to hit max rpms?

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2007 Horizon 200
4.3L GXi/ SX 225 HP