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  SuperSport 15, Johnson 70, SST II in 13x17

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Author Topic:   SuperSport 15, Johnson 70, SST II in 13x17
tedious posted 07-27-2009 08:01 AM ET (US)   Profile for tedious  
My SuperSport 15, with a Johnson 70, came with an OMC SST II in 13x17. Don't know why it had that prop on it, since it's clearly too short, but it had apparently been on there since new. So I found a Michigan Rapture 13x19 on eBay. It works pretty well, although it may be just a little tall - haven't had a glassy day myself to play with the trim.

This past weekend, just for fun, I put the 13x17 SST on. As expected, I could get to the 6K redline with a fair bit of throttle left. After a day of messing around with various kids, I took it out alone and scared myself. I was sliding along about 1500 rpm, off plane of course, and throttled up fairly quickly - not full throttle, but a good bit of it. Well, the bow basically went straight up in the air, probably at least 45 degrees before I could back off. I don't really know if it's possible to flip a 15 over backwards, but it sure felt like it.

I went right home and put the other prop back on. Yikes. Anyone want to trade me a 13x19 SST for my 13x17?

Tim

Tohsgib posted 07-27-2009 12:20 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
17 is a ski prop. 19" is a great prop but the rapture is a bit aggressve which should be fine. I had a 13x20 on mine and was just at 6k doing 48+.

No you can't flip one over but we used to do that and keep nailing the throttle and pulling it back real fast. You can actually make the boat hop out of the water. Try it, don't be a wussy ;)

an86carrera posted 07-27-2009 06:29 PM ET (US)     Profile for an86carrera  Send Email to an86carrera     
I have a 13.5 x 18 Raker by OMC I will trade.

Len

Tohsgib posted 07-27-2009 06:35 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
That would probably be a good fit for his 15. Rakers have some bite.
tedious posted 07-29-2009 08:00 AM ET (US)     Profile for tedious    
Hi Len - sorry for the delay, just noticed your post. I was mostly joking around about trading. I've really got to decide if I'm keeping the motor, otherwise it's not worth working on getting the right prop. I'm very happy with the performance of the motor at speed, but the idle is not great - as in it won't idle for more than about 2 minutes. Unfortunately, where the boat is in Maine, there's about 10 minutes of 'no wake' zone we need to get through routinely, so the bad idle is a major PITA. When it comes home from Maine, I'm going to try rebuilding the carbs and see if that helps.

Thanks for your offer, though - I'll keep it in mind when I decide what to do.

Tim

Tohsgib posted 07-29-2009 10:50 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Adjusting idle needs to be done on the water...running. It is called a synch & link. Do a search but usually a mechanic is best suited for it. Rebuilding/cleaning the carbs is a good thing but it probably won't help your idle. OMC's don't have idle adjustments, the use the butterflies...hence the term of synchronizing them, etc.
tedious posted 07-29-2009 11:06 AM ET (US)     Profile for tedious    
Yep, did the sync and link last weekend, didn't help much with the idle. I'm thinking the idle passages may be a bit gummed up, or maybe the emulsion tubes are leaking. The idle is great for about 2 minutes after you drop off a plane, then it goes downhill fast.

Tim

an86carrera posted 07-29-2009 12:59 PM ET (US)     Profile for an86carrera  Send Email to an86carrera     
Have to disagree with Nick. Clean the carbs, float valve and jets gum will ruin the idle qualities.
There are air bleed screws and they need to be adjusted while in gear in the water.

Len

Tohsgib posted 07-29-2009 01:31 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Sounds like you are running out of gas once idling. How does it do at say 1200rpm which is fine in a slow zone? I agree after last post, clean carbs but them synch them as well.
tedious posted 07-29-2009 03:06 PM ET (US)     Profile for tedious    
I think you're right, it's a fuel problem at idle. I have noticed that once the motor dies after a couple of minutes, I need to use the primer circuit to get it going again. Since I won't be able to work on the carbs for a couple of weeks, I think I'll test it - see if I can keep it idling by bumping the primer occasionally.

Len, my carbs don't have the adjustable air bleed, that came out later in 1989 than my motor was built. Since it is the air bleed that's controlled by the jet (in my case a fixed jet) then the fuel mix, at idle, must come through some relatively small, fixed orifices, right? Seems like one or more of them is probably plugged.

Tim

an86carrera posted 07-29-2009 03:47 PM ET (US)     Profile for an86carrera  Send Email to an86carrera     
Tim,
Check those float valves too I have had major idling problems with a set that had rubber tips on them that would get stuck at idle. At WOT they where fine, I guess the higher vibration would make them fall like they are supposed to.

Len

tedious posted 07-29-2009 04:27 PM ET (US)     Profile for tedious    
Thanks Len, I'll replace the floats, needles, and seats as part of rebuilding the carbs, but I won't be able to do that until I get the boat home. For now, I'm thinking of just pulling the idle air bleed orifice on each carb and giving it a shot of carb cleaner - doubt it will help, but don't think it can hurt.

Tim

Tohsgib posted 07-30-2009 02:16 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Can't hurt. Can you get to the bowl drains? If so you can fill them up with carb cleaner and let sit. Also do a search on decarbing an engine here. Sal & I have 2 proceses that can clean the snot out of your carbs without rebuilding them. Usually works if they are not completely stuck like yours.
tedious posted 07-30-2009 03:39 PM ET (US)     Profile for tedious    
Interesting thought backfilling with carb cleaner through the bowl drains - I may give that a shot. Right now, the field repair plans are:

- take out the high speed jet and idle air bleed, squirt in carb cleaner
- open the butterflies, reach through and poke a paper clip into the idle fuel orifices

Just trying to make things better while I'm on vacation, before I have time for a proper rebuild, so other ideas are welcome. I did a good decarb a couple of weeks ago - fogged the mosquitoes and annoyed the neighbors, so I think it cleaned something out.

Tim

Tohsgib posted 07-31-2009 12:06 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Go to Napa, etc and get a set of torch cleaning files($8) and use that to clean the jets/orafices instead of a paperclip. They are pretty long and come in a bunch of small sizes.
tedious posted 07-31-2009 12:26 PM ET (US)     Profile for tedious    
Thanks. I'm also getting some pipe cleaners.

Tim

Tohsgib posted 07-31-2009 12:34 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
The torch files are a kit, hence why they come in a bunch of sizes. For $8 or so they are priceless. I have to get a new set, I have broken/bent a few over the years.
tedious posted 08-12-2009 02:30 PM ET (US)     Profile for tedious    
Just a quick update from Maine on this subject - I did as good a cleaning as I could do in the field, and it didn't make too much difference. I was hesitant to strip the carbs right down and possibly lose some small part and goodbye vacation. The motor still runs perfectly at speed, but doesn't want to continue running below about 1200 RPM more than 20 or 30 seconds. It makes docking kind of interesting, but once you get used to it, not too bad.

My son is having a blast with the boat. We've been using the 13x17 SST, because the 13x19 Rapture is clearly too much prop - tends to overheat and I don't want to fool with it. Maybe once I get the carbs clean I'll be able to swing the Rapture, but I think it'll most likely go back on eBay. With the SST you've got to keep an eye on the redline, but it sure doesn't have any problem getting a heavy load up and moving.

Tim

Tohsgib posted 08-12-2009 02:40 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Once you do carbs, Rapture should be fine.
Sal DiMercurio posted 08-12-2009 04:10 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
If that engine is over heating, you better change the "T" stat & water pump, not.
It's "not" the prop that's causing the over heat situation.
Get youself a can of "Engine Tuner " [ Bombardier dealer ] or a can of Sea Foam [ Napa auto supply ] & decarbon that engine, odds are it will idle much better, as the decarb solution is fed through the carbs & should pretty well clean em out, along with decarbing the cylinders & piston rings.
Generally improves idle big time.
Sal
tedious posted 08-18-2009 11:26 AM ET (US)     Profile for tedious    
Thanks Sal. I've already done the decarb thing, and I regularly run Sea Foam to keep it in good shape. I'll be replacing the water pump and thermostat after the season. I know it seems like it can't be the taller prop that causes the overheating, but it does seem to contribute to it - I've tried enough that I think it's conclusive.

I know that the air and fuel also helps cool the motor, and my theory is that when running the taller prop, you're at a lower RPM and therefore getting less cooling. I think it won't be an issue once the water cooling is up to snuff.

Tim

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