I think it is just cursed

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OtisHelmke

Well-Known Member
Joined
Mar 30, 2015
Messages
81
Afternoon everyone,

I have a problem boat. It is properly built but has yet to run 3 feet under its own power. The question here is mostly about the engine. It's a D class boat, a HyPoint I got a while back. Power has been K&B 7.5, an engine I've always had good luck with in the past. The first K&B that I mounted was a never run pipe engine that to this day has not run more than a minute before quitting. I got fed up with it and mounted another K&B that was in good condition with low run time. It was running ok for a minute at a rich setting when the rod broke. Fuel is Omega 15%, same as I use in several 3.5 K&B engines and at least one other 7.5 that runs beautifully and has raced well in a HotShot Sprint. I have still another K&B 7.5 and a hull for it that is being painted. Is there some other 7.5 outboard that I can use on these boats? I'd like to race them but K&B parts not being all that common I'd like to find some other engine. What's available? If I convert to electric can I run it a D race? Or should I just take up sailing. Any help is appreciated.

Otis
 
Otis,

A few things to keep in mind.

if its clean on the bench its LEAN in the water. The motor should sound like crap on the bench. Make tuning adjustments AFTER a few laps.

Regardless IT WILL go around the pond rich.. just not fast.. we are OK with that for now.

IF.. a rich setting and the boat still stalls..

Your prop could be to big

or

Your motor is to low

or

Your engine bearings need replacement

or

Your fit of the piston to the liner is bad

Make sure after EVERY day of running you FULLY oil the motor. If you do not.. you will only get a few outings before your bearings need replacement.

Grim
 
Joe Monahan at 707 Specialties has K&B parts in stock and could help you out. Great guy! there is no one out there rite now with a stock 7.5. Lots of options for a mod with Nova Rossi and others with the Lawless leg and conversions. It keeps coming up that Nova may come out with an outboard but nothing yet as the marine engine is a small sales portion of the business.

Brad
 
what tank/tanks.. the outboards have enough issue pulling fuel as it is... stack a small hopper correctly to aid the engine drawing fuel... id almost switch to the bigger 5/32 tubing for the outlets also... a 45 needs fuel... last... maybe.. possibly check for a cracked fuel line in the tank at the bends especially .... new lines.... and... does the engine have crankcase pressure, ala mike z.. bearing leak, gasket leak, carb to neck leak.... too much for now... work on er and get back to us.... mike
 
Grimracer said:
Otis,

A few things to keep in mind.

if its clean on the bench its LEAN in the water. The motor should sound like crap on the bench. Make tuning adjustments AFTER a few laps.

Regardless IT WILL go around the pond rich.. just not fast.. we are OK with that for now.

IF.. a rich setting and the boat still stalls..

Your prop could be to big

or

Your motor is to low

or

Your engine bearings need replacement

or

Your fit of the piston to the liner is bad

Make sure after EVERY day of running you FULLY oil the motor. If you do not.. you will only get a few outings before your bearings need replacement.

Grim
Click to expand...
Mike you mention oiling your bearings. Do you use Corrosion X or WD 40 for that purpose?
 
I use an air tool oil as there is always some water in airlines. WD 40 is more solvent than oil and not a good way to clean out the engine after running. Corrosion X will coat the bearings.

Brad
 
Otis,

Grim has given you several items to check. Hopefully you can get yours repaired and back in the water. You asked about other engines available. I have Novarossi outboard engines in stock that will mount directly to that 7.5cc lower unit. Look at www.novarossi.us and you will find them. We have 21 and 46 outboard engines and are working with Novarossi IT on a 67 outboard next. The lower units are readily available and I keep a stock of 21 and 46 lower units and pipes in stock as well. Dont give up. This is a great hobby with a lot of great people.



Shown with optional remote needle carb.
 
Last edited by a moderator:
For engines with silicone filled crankshafts such as the 21DD and the 46DD you need to make sure you use something that wont eat into the silicone over time for an after run oil. I use Synthetic ATF.... Yes thats Synthetic automatic transmission fluid... Nothing real fancy it just works. I've found it to be a great after run oil that doesn't mess with the silicone and u can use to flush the engine at the end of the day to make sure everything is flushed/clean and free of moisture. A quart will last you a VERY long time!
 
Last edited by a moderator:
Good news.. the K+B does not have any glue in it..(SI Ramps and the like)

I have done a BUNCH of oil testing and have concluded that Corrosion X far out performs ANY other oils I have tested. I like Airtool oil as well BUT. its just hard to find anything better then Corrosion X.

Grim
 
I appreciate all the help. What makes this so annoying is that I've been running these engines in planes, boats and cars since I was

about 4 years old. It's a problem I've not run into quite this way before. These K&B engines are tight at the top and of course I can't

run them too rich without causing other problems. I'm getting the feeling that what I have here is some engines that just sat for

too long before I got them without proper preservation. Others are in great shape. After run oil is a standard with me in every nitro engine and I run

them dry at the end of the day. I'll get the two problem engines back together but I'm thinking a Nova Rossi is in the near future.

have a smaller one in a rigger that I need a prop for and expect great things from it but my emphasis at the moment is to get a

competitive D class tunnel built. I may upgrade my VS-1 to a Nova Rossi as well. If I am going to race more than once a year I can't

keep going on 80's technology.

Otis
 

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