www.iFourWinns.com

Not sure what's going on, but at the end of last season, and continuing into this season, the boat seems to not have 100% power. It used to max out at 4500 RPM and do 45mph on GPS. I could get onto plane easily with 4 adults and 4 kids with no issue. Now, it runs perfectly at lower RPMs and runs fine at WOT, which now is about 3300 RPM. At the top end it surges a bit and actually taking the throttle back a bit seems to help it out, but ends up going fine at 2800-3000 RPM. It is also a chore to get on plane with more then 2 adults, especially if seated in the stern jump seats. Any ideas?

Last year, I replaced the anti-siphon valve. Gas is clean, new filter end of last season and I have verified several times the gas does not separate when placed in a glass jar. I also put fresh fuel in it every couple of weeks all season. I have replaced distributor cap, all spark plugs, spark plug wires, module. All fuel lines are new when I redid engine, in 2013.

Any help would be appreciated. It runs fine, just seems not to have all power it used to.

_________________
1988 215 Sundowner 5.7L OMC

The first thing I would do is pull all the spark plugs and compare them. Sounds like you are not running on all cylinders.

_________________

"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

Do you still have the points distributor that was OE or was it upgraded to electronic at some point? If its still the Prestolite points distributor, you should check the points, dwell angle cap n rotor. Check the base timing and if you have an adjustable advance timing light you can check total timing advance with the boat tied up in neutral in the water. On the 5.7 the base timing should be 8* BTDC and your centrifugal advance at 3200 rpm should be about 20* so the total base+centrifugal should be about 28*. With an advance timing light the way you do it is to set the dial at the total number in degrees in this case 28. Hook up the tach to the battery terminals and #1 spark plug lead. Then warm up the engine (gotta be in the water to run it that fast) set the throttle at about 3200 rpm. Aim the light at the pointer and pull the trigger, if its right it should read right at 0 degrees or TDC, the light takes into account the total advance you dialed in. If its off the advance weights in the distributer could be rusted up and and not moving far enough to advance it to the correct degrees. If you have electronic, you probably can still check it this way but I'm not sure what you can do if its not right.
If you have a Petronix conversion I think the advance is still pure mechanical/centrifugal. On the Presolite when you pull off the rotor, in the distributor shaft there is a felt wick. You put a few drops of motor oil in there to lube the advance mechanism (very simple just 2 weights and springs). Like our cars were back in the day except they also had vaccum advance as well.

_________________
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

Not to completely send you in a different direction but what is the story on the carburetor? Is it stock? Has it ever been rebuilt?

_________________
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)

http://forums.iboats.com/forum/engine-r ... of-low-wot

take a look at this, its from DonS who was the best known tech on iboats, and covers all the possible causes....

_________________
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

He has the Delco marine dist package in it, and the carb was
new 2 years ago. If I remember , it is an Edelbrock 4409 or 4410.
( info from Dad) John Sr

Responses in red below. Must be an electrical issue, but will have to check the compression and linkage as well. I will also test spark plugs and wires again as well. Thanks for the tips everyone!

take a look at this, its from DonS who was the best known tech on iboats, and covers all the possible causes....[/quote]
1. Fuel condition. Type and Octane possibly old fuel - Fuel is good; no separation. Fresh fuel.
2. Propeller pitch or diameter, damaged blades - Same OEM stainless prop that I was able to do 45-46mph on GPS.
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test - Replaced anti-siphon valve last year. Perhaps do full test?
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse - oil is right amount.
5. Marine growth on hull and outdrive - bottom painted for first time this year. problem began end of last year without bottom paint and with no growth. there is no growth on bottom now. It went back on mooring a week ago and has no growth, not even scum.
6. Wrong gear ratio in outdrive - OEM outdrive and gears.
7. Restricted carburetor air intake (clogged flame arrestor) - will try running without flame arrestor to test, with engine hatch open and fire extinguisher ready.
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive - replaced in 2013 and engine has not overheated and runs at 160 on the dot.
9. Poor cylinder compression Compression Test - has not been done since rebuild, but would hope this is not the problem. will have to check.
10. Carburetor defective, or wrong type. - new in 2013, and should not be an issue. clean and fresh gas run through it since rebuild.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed. Loaded same as before when it performed perfectly.
13. Engine Overheating - has not overheated.
14. Engine timing and ignition system operation - will have to check timing
15. Remote control cables and linkage for proper travel to open throttle plates fully. will have to check. nothing has changed however.

_________________
1988 215 Sundowner 5.7L OMC

I've read about the Delco EST but I don't know how much total timing advsnce that system gives. I'd be interested to see what your results are if you can get a hold of an advance timing light.

_________________
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

We replaced fuel pump last week, but didn't see much of a difference. Tonight we used the advanced timing light and hit 6 degrees at idle, exactly what the specs called for. We also cleaned the flame arrestor, which was quite dirty. These seemed to help some. Gave more low end power for hole shot, but surged at WOT. Actually went faster when pulled back on throttle. We noticed choke, once warm, was not 100% opened. Turned out linkage inside had come undone. Still surged at WOT and went faster when pulled back. Took flame arrestor off and it added about 6 mph and 500 RPM. So it seems carburetor related....

Seems to be incrementally better, much better getting out of hole and acceleration is much better, but now to figure out why top end is not being reached....

_________________
1988 215 Sundowner 5.7L OMC

What was the timing advance, at say 3000 RPM?
Surging sounds like a lean AFR.
Could be blocked air bleeds or passages in your secondaries. Tear it down for a thorough cleaning.
What carb' is is? An Edelbrock 4409 or 4410 are both valve cover breather part #'s.

_________________
2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS

It's an Edelbrock 1409. Didn't time at 3000 rpm. Guess next step is clean it as you suggest. Do you think oem flame arrestor capacity could be remedied with aftermarket? The engine is a vortec with roller lifters, mild cam in rebuild with the aftermarket carb. Thoughts?

_________________
1988 215 Sundowner 5.7L OMC

If the F/A is clean, it won't be a restriction at these RPM's.
Remember to test your timing advance next time it's running.
Get a shop to professionally clean it & test the carb'.

_________________
2011 Four Winns H180 SS.
Aussie built Mustang 2800.
SOLD - 1997 Four Winns Horizon RS