1993fordprobe

hey, I have a 40" cat, running a OPS 15cc motor that i cannot get tuned. It has the external needle valve between the carb and fuel tank, and no matter what, i cannot get it to tach up in the water. Out of the water, I can get this thing to scream, but once it hits the water, there is no top end. I ran about 6 tanks of fuel through it yesterday trying to tune it, richening and leaning it, to no avail. Also Unless I am running it really rich, to the point were it is extremely hesitant and sluggish, It will make it out about 20 feet, and then just putter out. I am running 30% nitro, and have tryed 2 different props, and 2 different glow plugs mc-8 and mc-59 i beleave, I am not sure of the props, i have the boat at work, so i will find out later, also, i will take a bunch of pics of my setup, so maybe you can see something wrong with it. I am pulling my hair out here, a shockwave 36 whooped me all day yesterday [&o][&o] ANY help would be greatly appreciated, thanks. BILL

piper_chuck

My Feedback: (12)

DO NOT DO THIS!!! Running an engine up out of the water is a sure fire way to throw the rod.
That's the nature of boat engines. They need to be sloppy rich on the shore. If they're not, they die when you launch them.
When you post the pics, also provide some details, including what brand of pipe, length from the center of the cylinder to the widest part of the pipe, strut depth, etc.

1993fordprobe

ok, i still dont have the pics up yet, im working on it.
here is some other info i was able to gather though.
prop is an octura x462
exhaust is 15 3/4" long
2" at widest point
10 5/8" from center of cylinder to center of exhaust
fuel lines are 1/4" o.d. I am not sure, but i beleave 1/8" i.d. ???
40% nitro with 18% oil
oh the boat is actually 43"

please, i relly want to run this thing 4th of july weekend, but im stuck right now, the LHS cant help either, they say as it sits it should do 60-70, then again, they said run 15% nitro, and tryed selling me a cheap plastic prop.[:'(]

anyway, any info you guys could give would deffinately be appreciated, thanks.

Bill

1993fordprobe

oh one more thing, i forgot, the brass tubes going in and out of my fuel tank are really small, i have to use a zip tie on my fuel lines, or they fall right off.

piper_chuck

My Feedback: (12)

Hmmm. The prop is in the recommended range for that size engine in a cat, assuming you're running it as surface. Is the center of the shaft somewhere near the bottom of the sponsons?

Nitro content seems ok. McCoy MC-9 plugs work well for these higher nitro levels.

What's the condition of the engine? Does the compression feel good? Have you checked the bearings?

I've never run this particular engine, but it sounds like the pipe may be a bit short. A side effect of a pipe that's too short is it's very difficult to get the needle right.

1993fordprobe

here is the deal with the engine, it blew the glow plug out the top of the head and stripped the threads out, I have a buddy who races nhra pro stock bike, and is also a master mechanic certified in everything, I had trouble finding a new head, so i went to him, he welded the head up, re-tapped it, and reworked the dome, this may sound like a cobbled up job, but i assure you you cannot tell whatsoever that the head was ever worked on. And yes, the engine has great compression.

jetpack

My Feedback: (1)

I'm not a big fan of using exaust pressure for pumping fuel to a motor anymore, especially with racing carbs that have already poor draw. Maybe try a Perry fuel pump, it's healthier for the motor because the fuel delivery to the needle is consistent through the entire tank. A bit more cumbersome inside the hull, but once its installed there's no more guessing why the motor isnt getting fuel or finding out your boat leaned out at the end of the run and cooked itself. I look at pumps as an insurance policy...you might not think you need it, but when things go wrong you wish you had one.

1993fordprobe

thanks jetpack, im still open to suggestions though.

were can i find these fuel pumps?

jetpack

My Feedback: (1)

Perry Aeromotive makes them, and can be bought from them or through online hobby shops like Tower Hobbies, or snag a new/used one off of ebay. The setup is going to cost near 50 bucks, and you'll have to add a pressure tap to your motor, a couple of fuel line T fittings, and a check valve to the vent on the tank. They come with a short stiff pressure line, a pressure nipple, and a strap to mount the unit and instructions. I dont know why they dont include T fittings or a check valve.

There are three or four types, just get the fuel/nitro version which has a blue anodized case. If your looking at older ones, they are silver with a red plastic housing instead of black that they use now.

http://www.perrypumps.com

http://www2.towerhobbies.com/cgi-bin...ry&FVPROFIL=++

Once you get your OPS running good, you'll be impressed. I've seen a couple of your size run in outriggers. Very fast.

Pamper that motor though because OPS is gone now and the parts availability is going to dry up. I would look into buying an extra connecting rod as a spare, thats usually what gets hurt the easiest. I think your motor has needle bearings top and bottom that can be replaced but the rods still bend or stretch sometimes before the piston/liner has had it and it might be a season or two before it happens.

1993fordprobe

thanks for all the info jet pack. But im starting to think maybe i should get another engine all together, i know that buying a fuel pump isnt going to solve my problem all together, this motor just seems really tricky to tune. And with it being so hard buying parts, maybe i should move on.

piper_chuck

My Feedback: (12)

OPS parts are available at Aeromarine and other dealers: http://www.aeromarinerc.com/opsengines.htm

As for the Perry pump, I don't recall seeing anyone run one. Pipe pressure supplies a significant amount of fuel flow. Also, since boat engines don't usually have to pull the fuel up very much, flow shouldn't be a problem.

Any engine you get will require some tuning. I've never found OPS engines to be particularly fussy. Unless your engine has a problem, replacing it may not make things any better. Keep working on it, and get us some pics of the engine area, fuel system, pipe, and strut/shaft location so people can take a look.

1993fordprobe

here are the pics, cell phone quality, so i dont know how good thery are. hope they help.

mavgrab

can't really see much in those pics. I am assuming you know how to set your needles and the effects they have on your engine. Maybe you should go with a fuel around 20% nitro, with 40% you have to run a lil richer and if the engine isn't already broken-in. Being if you richen it up and the engine responds tells me it isn't fuel flow nor do you need a pump. I'm thinking maybe you scarred the sleeve and makes the engine seem like it runs differently eachtime you take it out. Did you over rev it out of water/ get it hot, if so your compression will change once the motor heats up/cools, making it suck more fuel/less fuel. Thats why it is so hard for you to go through a proccess of elimination. But again I'm not looking at your boat..lol