'92 Euro F3 Sunsetter - Carb Issues

[Michigan boarder]

I think someone converted yours to an electric choke at some point, it was probably a manifold choke similar to mine originally.

[CaptnHk]

1 hour ago, Michigan boarder said:

I think someone converted yours to an electric choke at some point, it was probably a manifold choke similar to mine originally.

I was looking at the original carb that the seller gave me in a box... it does look that way...  I don't see anywhere to put that hose though, so it's disconnected for now.  That vacuum connection though, I think I need to cap that off to not lose the vacuum right? the only vacuum thing I see is the small cylinder that sucks in and moves some linkage in the back corner of the carb (sorry, no good at part names)..this still moves though with the front hole open...

Thanks everyone for the help!  I'll get there, learning on the fly.

[MadMan]

33 minutes ago, CaptnHk said:

I was looking at the original carb that the seller gave me in a box... it does look that way...  I don't see anywhere to put that hose though, so it's disconnected for now.  That vacuum connection though, I think I need to cap that off to not lose the vacuum right? the only vacuum thing I see is the small cylinder that sucks in and moves some linkage in the back corner of the carb (sorry, no good at part names)..this still moves though with the front hole open...

Thanks everyone for the help!  I'll get there, learning on the fly.

Maybe your carb isn't a "marine" carb.  Only marine carbs have the port to connect this hose to (and they are rare and more expensive than the automotive counterparts).

And yes, you should cap off that open port.

[CaptnHk]

I now get about 4500 @ 41-42 mph...and it feels like a boat again! I am thinking I should be able to see 4800 rpm and 44-45 mph with this setup...?  Maybe this motor is just tired... thoughts on how to get a couple more mph without sacrificing hole shot? (I need a good hole shot for slalom starts )  I hope to actually ski behind it this weekend...now that its running good.  Would there be any carb tuning? or would this be a more major tweak and I should look at props...  it's running a 13x13 stainless.  I have the original 13x13 brass in a box.

[Woodski]

@CaptnHk:  It appears your prop may need some tuning, should be closer to 100 RPM : 1 MPH and you would see pretty close to 45 mph @ 4500 RPM +/- a few.  Is the prop in good condition, does not take much to affect performance?  The stainless should be a CVP, and there should be some markings on it telling you what it is.  There have been some blade throwing issues with CVP props so take care as once it throws a blade you are dead in the water.  The latest CNC props can provide some improved performance, Acme and OJ are the primary manufacturers and they are very good propellers.  What is you brass one?  If an older cast version, probably less performance than the CVP but you don't know until you give it a try.

Certainly some engine tuning can help, we don't know the condition of your engine so hard to tell.  Set the ignition so that you get 32-33 degrees BTDC @ 4000 RPM (that is not the timing at idle, that will be closer to 8-10 degrees BTDC @ 750 RPM).  There are some carb blueprinting things that can help, several books available to guide you along.  The key gain for that engine will be updating the cylinder heads to the post 1996 Vortec heads, they flow more air and bump the power level from 265-285 to 310 hp.  Check your spark arrestor to make sure it is clean and you might do an A-B with and without to ensure it is breathing enough air.  It takes a lot of additional horsepower to increase top speed, there is a lot of hull drag on a ski boat hull.

[CaptnHk]

1 hour ago, Woodski said:

@CaptnHk:  It appears your prop may need some tuning, should be closer to 100 RPM : 1 MPH and you would see pretty close to 45 mph @ 4500 RPM +/- a few.  Is the prop in good condition, does not take much to affect performance?  The stainless should be a CVP, and there should be some markings on it telling you what it is.  There have been some blade throwing issues with CVP props so take care as once it throws a blade you are dead in the water.  The latest CNC props can provide some improved performance, Acme and OJ are the primary manufacturers and they are very good propellers.  What is you brass one?  If an older cast version, probably less performance than the CVP but you don't know until you give it a try.

Certainly some engine tuning can help, we don't know the condition of your engine so hard to tell.  Set the ignition so that you get 32-33 degrees BTDC @ 4000 RPM (that is not the timing at idle, that will be closer to 8-10 degrees BTDC @ 750 RPM).  There are some carb blueprinting things that can help, several books available to guide you along.  The key gain for that engine will be updating the cylinder heads to the post 1996 Vortec heads, they flow more air and bump the power level from 265-285 to 310 hp.  Check your spark arrestor to make sure it is clean and you might do an A-B with and without to ensure it is breathing enough air.  It takes a lot of additional horsepower to increase top speed, there is a lot of hull drag on a ski boat hull.

@Woodski, thank you for that info, VERY helpful.  I will have to take a close look at the props and see what I have...I was already thinking I should be about matching the RPM for speed (45=4500) so slower speed at 4500 makes sense to look at the prop as it's maybe out of whack a bit.

I was told by a merc mechanic that I should be at 12 degrees BTDC which is what I set it at (at about 1000 rpm based on the gauge)...although the gauge seems to not react very quick with rpm change (especially low RPM range) so I still need to verify the connections on that and then re-check the timing.  I assume checking timing at 4000 rpm means run it on the lake... 4000 on the fake-a-lake seems risky to me 

That's quite the bump in HP with new heads!... I'll think about that down the road... don't want to pour money into it before I really get to enjoy it this season.  I'm just happy it's where its at now (and my young boys enjoyed the cruise yesterday!)

weather for tomorrow morning looks better than it was predicted a couple days ago so I hope to get it out and ski a couple sets on it...today got away from me and i'm busy rest of the evening too... the wake at 30 mph lays down super nice so I can't wait to cut across it and throw some walls up on the slalom!

[Woodski]

@CaptnHk:  You are welcome.  You can do a timing check in the lake in neutral which is safer than on shore, fake a lake is okay just don't hold it there long, a quick burb should tell you.  Your raw water pump flows ~10gpm for every 1000RPM so you can do the math for higher speeds.  12 degrees is probably very close, it does depend on which timing module is in your boat, you can google the P/N to find the actual timing curve.  That GM cylinder head improvement is nice, you can find used heads off old GM pickup trucks or salvage if you want to save money, the intake manifold bolt pattern can be an issue so need to do the research for that.

[justgary]

Good you hear that you got it running.

Before you toss it out, is your stainless 13x13 a three or four blade?  If it is three, it is probably a CVP.  If it is a four blade, it probably isn't (and I will buy it from you if you want to sell it).  In any event, I have a CVP three blade on my boat, and I trust it completely.  I also have a second CVP that Boz gave to me, and it clearly has a blemish in the hub from what looks like cold casting.  I don't trust that one as much, and it is only an emergency spare (although I have run it on the boat to test it).  The bottom line is that almost everyone here will tell you that a CVP is a time bomb, but close inspection should tell you if you have a good one or not.  Besides, if your old time bomb hasn't gone off by now, it probably won't ever.

They will also tell you that you should not use a stainless prop on an inboard.  I disagree, since it is a logical choice where I live.  I boat mostly in salt water, we have no rocks (at all), almost no junk floating around, and pure quartz sand everywhere.  I'm a lot more likely to need the toughness of stainless than the tenderness of bronze since I'll run through sand many times before I ever hit anything hard.   Make these choices for yourself (after educating yourself on your choices) based on your conditions.

[Woodski]

A magnaflux test will tell you if there is an issue with a prop blade.  I did some tuning on my CVP and it performed very well.  As @justgary noted there are many still out working just fine, including my neighbor who still has his original on a '97 Response.

[CaptnHk]

Ok, boat has been running good (out on the lake, I'd swear it was EFI with how easy it restarts!) but still need to figure out what to do for a prop.  Love how the wake lays down as you get to 30mph!

I was getting ~4500 rpm @ maybe 42mph (more like 41.8 as it occasionally bumps 42 on the gps app on my phone) with the 3-blade 13x13 stainless.  I took that off and laid it on top of the brass 13x13 that the seller gave me and the brass one had more blade on the leading edge. (also 3 blade, and it's the cast type).  I put the brass one on, as Wisconsin lakes aren't the safest   and my results are a slight bump in RPM (if I recall correctly, it was 4600-4700) but about 1 mph slower.

So, I think I need to get a new prop, maybe try to sell the 3-blade stainless 13x13 and hang on to this cast 3-blade as a spare.

Is there a different sized prop I should look for or stick with 13x13 and make sure it's the newer CVP type?  I'd like to see 44-45mph so that I could get 1-2 people barefooting with it (assuming it'll drag down to 42-43...), but without losing the hole shot as I feel comfortable deeping up on a slalom as it is now.