Ok, so I checked the barb fittings on the cooling head and true as ..... it's the kind that reduces! From the outside it looks like nice big 3mm hole...check the other side, the part that sits inside the block, it's only 2mm. Will drill it out before race day this coming Saturday.

Also checked the water channels in the rudder...they're not blocked, but did find a white residue inside them. Maybe the aluminium that's corroding a bit? Also found that the holes where the water enters the rudder is also only 2mm, the ones running up to the barb fittings are 3mm. Gonna drill those out as well.

Internal screen is a very good start. Insulator between the carb and jug. Warped, bad gaskets. Try running it on a stand. At idle, Spray a lil carb cleaner on the insulator. If it stalls that's the prob. Flywheel key sheard slightly? Or ya muffler plugged.

Like Les said - I drill out all the stock fittings --- I use XL water line - and on the rudder I open it (and holes) up some - I don't use the XL water outlet because I like to 'see' the spray when it comes by so I use Pro Boat stainless out fittings (not too big but gives good flow and I can see the flow) some of the XL outlets are so big water `dribbles` out and hard to see at a distance

If any of my stuff starts to show any major corrosion (white residue) - I simply replace it.

Here is a rudder blade on mine






Here is a rudder

Thanks for all the replies guys. I really appreciate it!

I drilled the rudder holes out to 2.5mm last night. I also drilled the nipples out on the cooling cap. Still to check the fuel filter or even remove it. Also needs to check the isolator block and gaskets.

Come race day tomorrow I'll take the stepped water nipples with as well. Gonna be a cold day tomorrow during racing.

My hull exit nipples are very very big in diameter...quessing I think it's about 6mm. Maybe I should look at some with a smaller diameter. Will make it alot easier to see the stream when sprayed further from the hull.

Yesterday I was informed that the rules of my class state that I may not remove or add material to the engine in any way what so ever and that the parts used must be as it it supplied by Zenoah. So strickly speaking I'm running a mod motor now just by drilling the holes in the water nipples of the cooling cap bigger. I replied that they can disquilify me if they so wish!

Still don't know which steel tune pipe to look at? Seeing that it must be a 7/8th header and a one stage diffuser and baffle cone and it looks like most of the decent pipes available these days have two stage diffusers...will see if I can find anything worth looking at.

If any of you guys are also racing this weekend, good luck and WOT all the way hey! For those who are planning to go play at the local water spot...have a blast!!!

Thanks again for all the replies, I really appreciate it.

SamCro,
I hate to disagree with some of the help you have received, but I can tell you I run in high 90 degree weather with 80% humidity on a regular basis and have never drilled any of the fittings or rudders on any of my boats and have no problems with engines overheating. When your boat is up at speed the pressure and velocity of the water traveling through your lines will actually do a better job cooling your engine if it gets slowed down some as it will get a better opportunity to absorb and radiate the heat from the cylinder. The fittings are stepped for a reason and I have to laugh every time I hear someone tell guys to drill out the fittings on there water jacket as they they actually do a better job undrilled. Everything you have described from the engine smelling hot, plug looking fat to the needles not really taking small changes is all clear signs of the engine being under too much of a load. Reasons for this usually are too big of a prop or too much prop blade area of the prop in the water (Too Deep) which keeps the engine under too much of a load and never has the chance to free up. When this happens it makes the engine hard to tune, causes excessive heat and always makes for a fat looking plug. Think of it this way, you have a hot rod car that runs great when it is on it's own. Then you strap a 40ft trailer to it and it does not want to get up and go, it runs hot and it can't burn the fuel efficiently because it is under such a load and it makes the plugs look fat. Too big of a prop or having your prop too deep into the water does the same thing.

The solutions to this problem is to raise your strut straight up to get some of the prop blade out of the water or try a prop with a little less pitch to allow the engine to spin up free without so much of a load on it . The engine will free up run cooler and you will notice that the engine will respond to carb settings and the plug will also start to burn fuel efficiently and not look fat.

Good luck and let us know how you make out.

Carlo

OK 1 question? How is he adjusting the carb? If out of the water and under no load. He gets no responce from the carb settings then what?

Gulf Coast,
You should never adjust your needles out of the water with no load.

Carlo

If out of the water and there is no change on adjusting the needles .. the issue is either with the carb or a leak at the carb manifold, cylinder base or crank seals.


SamCro- I finally had a chance to view your pics and is there a reason why you do not have water cooling on the pipe to header connection?

Also Zenoah has two different inside diameters of their barb fittings with the same part # so drilling them out will make it illegal and finding the larger id still makes it legal.to use.

How did your boat perform over the weekend?

CC Racing Engines: Thanks for your advise. I agree with you regarding the water fittings and I actually fitted the stepped water fittings on race day. I also agree with my prop loading the motor too much causing the motor to run hotter than normal and thus causing the said issues. I run a Propshop UK 7015/3 chopper (hull does not like cleavers). The past few race days the water were fairly flat and 'dead'. Even with the strut as high as it can go the boat will not be as fast and also fall of the pipe in corners. BUT, with a fair bit of chop on the water the boat are really really fast and does not come of the pipe in corners...so mayby my prop are not suited for flat water and thus causing too much load on the motor. And when I mean faster I mean that I'll be able to enter the main straight behind a boat and 3/4 down I'll be passed him. I'm waiting for a ABC prop...don't know what it is, but I've tested one on the boat not long ago. The water were flat and just by changing the props the boat were already a second faster per lap.

Gulf Coast: I adjust the needles by running the boat on the water.

Performance Unlimited: No water cooling on pipe to header' because I don't have orings there...no need. The header and pipe are a very tight fit and the clamp is enough to seal it.

The morning of race day we made some adjustments and played around with needle settings and stru heights and pipe lengths. Didn't get any real performance increases, but did find the high needle to be set on 1-3/8 turn from in...way to rich. We took it down and eventually settled for a setting of 1 turn from in, because racing were about to start. We'll spend some more time on fine tuning the boat during the off season regarding pipe lengths, differant pipes, needle settings and props.

So Saturdays' racing went fairly well. Going into the first heat I was some 800+ points behind 3rd place for the club championship. We were only 4 boats in our class...the least amount for the whole year! During the 1st heat he decided to flip his boat, giving me a easy 2nd for heat one. During the 2nd heat he decided to run across my rooster tail on the start of the race causing my prop wash to flip him...obviously according to him it was my fault, but everyone told him he changed lanes on the way to the first turn were I and everyone else kept our lines. Come the 3rd heat he did it again, but this time with someone else. So going in to the last heat for the day, and season, I managed to get in to 3rd place overall, by 2 points, for the club championship. So who ever finishes the last heat ahead of the other will be the one to take 3rd position for the season. I made some mistakes during the first few laps and thus I found myself in 3rd place with him in second and me with some catching up to do. Concentrating on running tight lines I eventually caught up with him with less than 2 laps to go. In the last two laps I just could not find a way past him, even running alongside him some times, and thus finished in 3rd place with him in second. So I finished 4th overall for the season and I guess it's not bad considering that this is only my second season of racing and with a new boat that we still setting up and sorting out.

Again thanks to all who've replied. I'll keep you guys informed on what we've checked and tried and what the outcome was.