'87 F351 only reaching 3100 RPM WOT and 35 MPH

I have an '87 sunspot with an f351 which is running smoothly but I'm not reaching the speed or rpms I should be getting at WOT (3100 rpm, 35-36 mph). I'm not familiar with working on carburetors, but is there an adjustment that I can make to increase my top end speed? Am I right in thinking I should be getting another 1000 rpm and around 42ish mph? Also I'm not sure what prop, I have on there. I'll have to look next weekend. Is there something I should be looking at other than the carb and prop? Any suggestions would be helpful.

It is possible your carb needs attention, but that is usually accompanied by stalling, rough idle, rough running, etc. From what you've described the problem is probably your prop. Do you live at altitude?

Have you done any maintenance? Keeping ignition in good shape(coil, plugs, plug wires, rotor, cap, points and condenser!), good fuel filter, clean oil with a cleaner so it keeps the motor clean, non-ethanol fuel... etc

Make sure things are good shape before blaming the carb...

I could check points and cap. I changed the oil, oil filter, fuel filter/h2o separator, new plugs... Condenser was new last year, no idea on the coil. The previous owner did switch props at some point and we couldn't find the other one when we bought the boat a few years ago i'll have to ask him what he had on there and what and why he changed. I know it wasn't for surfing cause he's In his 80s haha. I'll sit down and have a chat this weekend. Thanks for the input, I'll check those things out. Oh and Supracomp I think I'm on your lake...Keuka?

Keuka Lake, NY? If so, yep! What year is your boat? If its a 1:1 direct drive, you should have a 13"X13" also, check the condenser! Don;t trust Bosch anymore, they are no longer best (sad huh?), many people are having problems left and right with cheap points and crap condensers out of the box...

For your carb, now its dangerous but sure is a great way to see whats going on, is to: Take off the dog house and have someone else drive at WOT and watch the carb with the spark arrestor off. See if the secondaries are opening up and see if the venturies are flowing correctly, you might have some crap plugging up the carb... And if the secondaries aren't opening up all the way, open them up manually and see how she runs!

Fuel pump? Being an 1987 it might be a good idea to replace it anyway, $89.00 from skidim

I'm with 92SupraComp, sounds like the secondaries aren't opening, that's the first place I'd look. Are you new to this boat or have you seen it running in the 40mph mark?

I did have a condenser problem last year right out of the box... is that something that needs to be replaced often? They are pretty inexpensive so I can definitely do that, I'll check the points too. Should I consider just getting a kit from Skidim with a Cap, Rotor, Points and Condenser? Or should I see if things change piece by piece? Oh and what do you guys use to clean off the spark arrestor? I'll have an extra hand this weekend to check out the carb...I'm guessing I'll have to be the one to stick my head over the engine, haha. I'll take a look at the fuel pump, I have no idea when that has been replaced in the past, if ever.

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Originally Posted by chris young

I'm with 92SupraComp, sounds like the secondaries aren't opening, that's the first place I'd look. Are you new to this boat or have you seen it running in the 40mph mark?

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This is our 3rd year with the boat, and previous to that our neighbor owned it since the late 90's I think. Never was in the boat at WOT when he had it. Last year when I was on my last cruise before pulling her out I got her up to 39 mph, but most of the summer WOT was at 37ish.

A good condenser should last for years. Points used to be solid hard metal (I think titanium) but now to save money are only COATED. Thats why filings points no longer works... Condensers seem to be hit or miss now, really if the motor is miss firing I would suspect a condenser. Make sure your gap and dwell are set right. Also, CHECK TIMING! When we first got our CC it was at 2 degrees BTDC. Set it to 10* ran great. Two years ago in NH with family, it was a dog. (was full with 10 people though, and we were trying to ski haha) Got back to Keuka Lake and found the timing at 1* ATDC! Set it to 11*~12* runs great again! But with the timing set way behind it was really missing its top end... The reason for it retarding on its own is because the coating on the points is gone and the cheap filler material is wearing away fast. Will Probably have to reset timing again this year...

Hey, I got to meet OP today. Let me know and we will lend ya hand on the timing if you want.

Damn, I haven't looked at this site in a bit. I might be able to make it to the lake in the next few weekends... I could definitely use an extra hand when I get to working on the boat again. First I think I need to put the decking back on our dock after all the flooding, taking a row boat out to the lift is a pain in the ass.

Hey did ya hear, they lifted the boat ban today!