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Trouble with Inboard Engine

Old 02-27-2006, 12:36 AM
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tex1790
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Default Trouble with Inboard Engine

I am having one major problem with my nitro boat. I have had it now for over 6 months and I have had it running a few times.

I have a 43 inch Fountain Hull with a MAC .67. I was told when I bought it that it was bored to a .70. I couldn't even tell you how to go about checking that. I have been running a 20% nitro (mixed by the LHS). The fuel sat around for a few months, I threw it away and bought a different fuel (Hobby shop was closed due to Hurricane Katrina). I am now using White Lightning 20% w/ 8% oil content. This boat has a big bore carb with a fuel control valve (no high/low speed needle valve).

I can not get this puppy started. I changed out glow plugs, used washers for glow plugs and not used them. I have opened the fuel valve halfway, all the way, and almost closed. I used a high torq starter and used my truck battery, of course it is belt started.. The engine has a lot of compression I have to loosen the glow plug a 1/4 turn to almost half way out. I have used hot & cold plugs. I moved the fuel tank from a lower position to a higher position.

I did pull the engine and bench test it and it ran fine. It started on the first bump.

I have done everything imaginable. I am at my WITTS END HERE

I hope that you guys could help me with the issue.
Old 02-27-2006, 02:37 AM
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ob nut
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Default RE: Trouble with Inboard Engine

First off, the oil % needs to be up around 18%, not 8%.. If you do get the motor started, it'll be destroyed quickly with that low % of oil. Secondly, who ever told you the motor was bored to .70 is smoking crack. These cylinders can't be bored as the liner is chrome plated. Get ahold of [link=http://www.cmdracing.com/updated/main.htm]CMDi[/link] for proper information on this motor.

Sounds odd that it'll start on a bench test but not in the boat. Fuel lines new? Tanks sealed properly? Tank pressure from pipe? A "high torq" starter might not be enough. Think about getting a 24v starter, that may help greatly.

Sorry I can't be of more help..

BTW: I have fuel purchased last year and plan on running it this spring. As long as the fuel is stored properly (not in sunlight, cool temps, cap on tight) it should last for awhile.
Old 02-27-2006, 05:41 AM
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Ron Olson
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Default RE: Trouble with Inboard Engine

The MAC's need to be fired up at 1/3 opened throttle and yes, somebody is smoking something good and not passing it around!
If you're having problems getting it fired up in the boat, look for driveline drag that could be adding a little extra load to the engine but something just doesn't sound right.
Get rid of that White Lightning!!!!!!! I would be scared to run that junk in any R/C vehicle as the oil content is too low unless you like to replace engines a lot.
You mentioned a fuel valve. Are you talking about a remote needle? Andy Brown (CMDi) sells 2 of them, fine and coarse versions. You need the latter and large fuel line, not medium it can't handle the amount of fuel that the engine needs.
Old 02-27-2006, 09:48 AM
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Default RE: Trouble with Inboard Engine

Thanks for the information. I will contact CMDI and explain what I have. I have pressure tested the fuel tank and it works fine (does not leak, though it is a little used). It does have a remote needle valve controlled by a 3rd servo. I was told to run a high nitro with a low oil content. Do you guys have any suggestions; Odonnel, cool power, blue thunder, red alert???? I will contact the guy I bought it from and get more info. Maybe that would help also. Thanks.
Old 02-27-2006, 10:10 AM
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Default RE: Trouble with Inboard Engine

What brand fuel that you use isn't the issue but the percentage of oil content. Andy likes to run a lot of nitro through his engines so 60% isn't uncommon to him but he'll tell you that it's safer to run 18-20% oil, usually a mix of castor and synthetic.
I'm not a fan of O'Donnell's but that's me. I've used it and found a lot of creosote-like build-up in my headers and pipes. Just get a fuel that's made for boats and/or possibly helicopters.
The guy that you bought it from has already stuck it to you, especially the story about it being bored out to a .70 so I'd question his reliability.
If you call CMDi, you'll probably get one of the ladies answering the phones. Don't worry, they're good at their job and most don't look too bad either. A few of them are his "poster girls" on his website!
Old 03-01-2006, 06:30 PM
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Default RE: Trouble with Inboard Engine

Ok I bought a new Sullivan 16 oz fuel tank. I replaced all of the old smaller fuel line with larger fuel line with the exception of the pressure line comning from the pipe. It will pop pop pop pop pop then it will back fire. I tried looking for a new needle valve at the LHS but they did not have one. Here are a few pictures maybe you can tell from them.
If anyone is local that can help please e-mail me.
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Old 03-01-2006, 09:47 PM
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Default RE: Trouble with Inboard Engine

Sounds to me like the rotor may be installed improperly. Not being familiar with the MAC 67, it that possible? The report of firing but not running sure sounds like that's the problem.
Old 03-01-2006, 09:56 PM
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Default RE: Trouble with Inboard Engine

I am not sure what you are talking about. Rotor? Are you talking about the rotor for a spark?
Old 03-01-2006, 10:04 PM
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Default RE: Trouble with Inboard Engine

No, there is a disc inside of the backplate that times the intake of the fuel-air mix. On a lot of engines of this type, it is easy to re-assemble the engine with the disc 180 degrees off. Some are notched and some can be put together where the timing isn't 180 off but less as the crank pin can just push the disc around.
One somewhat easy way to check is to look down the carb with it wide open. If the crank is at BDC, you should be able to see down into the engine a little. If not, then the backplate will have to come off. Have fun as it can be a pain in the butt to get back together right.
If the previous owner "modded" the engine, he probably had it apart and may have put it together incorrectly.
Old 03-01-2006, 11:05 PM
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tex1790
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Default RE: Trouble with Inboard Engine

Ok I pulled the head off and the carb and this is what I see. When the piston is at top dead center the crank is fully open, when the piston is at bottom dead center it is closed. I am not sure if the crank should be fully open at BDC and Fully closed at TDC???? I sure wish I could show you what I am seeing!!!![:@][:@][:@][:@][:@]
Old 03-02-2006, 05:05 AM
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Default RE: Trouble with Inboard Engine

ORIGINAL: tex1790

Ok I pulled the head off and the carb and this is what I see. When the piston is at top dead center the crank is fully open, when the piston is at bottom dead center it is closed. I am not sure if the crank should be fully open at BDC and Fully closed at TDC???? I sure wish I could show you what I am seeing!!!![:@][:@][:@][:@][:@]
I thought this sounded correct, but I just looked at one of my .45s to confirm. The thing you are seeing is called a barrel rotor. It's designed to be open to allow the engine to draw in air/fuel and closes to prevent the piston from forcing the air/fuel mix back out the carb.

I've observed lots of engines popping as you described. It's usually a sign that it's almost ready to start. I think it may be getting not quite enough fuel. Your setup has a remote needle valve, try opening it a little more. Also have your helper open the throttle a little more, but be sure he's ready to back off it a bit once it starts. One of the worse things you can do for an engine is to rev them way up with no load. It's typically necessary to pulse the throttle (kind of like some Harley owners do at a stop light) while the boat is on the shore. The idle setting will be sloppy rich and the pulsing helps keep the engine from loading up with fuel and stalling.

You might also want to try choking it a little bit. You can do this by putting a finger over the carb while you are spinning it, or an easier way for some boats is to put your finger over the end of the pipe (assuming it's not hot), the pressure will force a little extra fuel through the carb. Which ever way you do this, be careful to not flood the engine. If it becomes more difficult to crank, it's probably flooded. If this happens, remove the plug, hold a cloth rag over the engine and give it a little spin.

Edit: there are lots of boaters down your way. Think about contacting them to see if you can hook up with a club. Go to the [link=http://www.impba.net/]IMPBA web site[/link] and click on "Districts & clubs"
Old 03-10-2006, 01:10 AM
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Default RE: Trouble with Inboard Engine

Ok I just cam e back from vacation and have the weekend off to work on the boat. I will look at the website to see what I can find. As far as choking it I have done it. I did flood it and have unfloaded it by turning it over and letting the fuel run out and bumping it over. As far as the needle valve goes I have had it open all the way, 1/4 turn from closed, 1/2 way..... Well oyu get the point. I even placed the fuel line directly to the carb bypassing the needle valve. I guess we will find out here soon.
Old 03-13-2006, 05:19 PM
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Default RE: Trouble with Inboard Engine

hey you fancy selling the boat if its still causeing you probs?? how much you want??
Old 06-17-2006, 11:13 PM
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Default RE: Trouble with Inboard Engine

Ok I can get the boat running now but it bogs down. Here is what I am going to do. I am going to buy another engine for the boat. A new engine nothing used. I am wondering do I go bigger like MAC .87 or should I stay the same? It is a 42" Fountain hull. Do any of oyu boaters have a suggestion. I looking for ease of starting and ease of tunning. Let me know
Old 06-18-2006, 07:26 AM
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Default RE: Trouble with Inboard Engine

ORIGINAL: tex1790

Ok I can get the boat running now but it bogs down. Here is what I am going to do. I am going to buy another engine for the boat. A new engine nothing used. I am wondering do I go bigger like MAC .87 or should I stay the same? It is a 42" Fountain hull. Do any of oyu boaters have a suggestion. I looking for ease of starting and ease of tunning. Let me know
Do you think the engine is broken? There are many more things to check before you give up on the engine, including sending it to Andy Brown at CMDi to have a look at it. I sent one of my .45s to Andy last fall to have him put in new bearings and evaluate the condition of the piston/sleeve. He did a great job on it and the price was way less than I thought it would be.

Anyway, now that you have it running, here is list of the next round of things you will need to start looking at:
1) What is the distance from the center of the cylinder to the weld?
2) What props have you tried?
3) Is it setup with surface drive (shaft exits the transom) or subsurface (shaft exits under the hull and then curves to be parallel to the bottom of the hull)?
4) What nitro percentage did you end up with?
5) What's the condition of the bearings? If they don't feel perfectly smooth, they should be replaced.

I'm sure there are more, this is just a beginning...

Buying a new engine will not make your life any easier unless the one you have is worn out. Even with a new engine, you're still going to have to go through the above considerations and more to get it running right.
Old 06-18-2006, 08:54 AM
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Default RE: Trouble with Inboard Engine

It looks like your 3rd channel linkage isn't hooked up, that's OK for now. Make sure that the arm is bottomed out. I'm hoping that the remote needle is the coarse threaded one. Take it out about 2-1/2 turns. With the throttle 1/3 open, it should start (hopefully). The MAC engines like to run slobbering rich on the bench or out of the water.
It does appear to be an older engine, the newer ones all have blue anodized heads.
I'm thinking that the intake rotor may be 180 degrees off yet. I really hate pulling off the backplates from these type of engines as thewy can be a real pain in the rear to get back together but that might be what you have to do. Otherwise, send it to Andy to have him take a look at it.
Old 06-18-2006, 11:24 AM
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Default RE: Trouble with Inboard Engine

It seems that the consensus is to send it in to Andy @ CMDi. I will do just that. I will have him take a good look at it and recondition the whole engine if need be. I have been to his website quite often looking at the MAC engines there. Thanks for the advice, I should have done this a long time ago.

To answer your questions:
1. I have not had the head off of it yet.
2. The original Octura prop that came with it, I am not sure of the size due to the numbers being worn off.
3. She has a surface drive.
4. Bluethunder 20%
5. I have not felt any burrs or resistance when turning it over. It seems to be pretty smooth.

Thanks
Old 01-25-2010, 09:30 PM
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Default RE: Trouble with Inboard Engine

hey bro what ever happnd with your motor? im having the same problems. did you send it to cmdi and how much did it cost for them to look at it and fix whatever was broke?
Old 01-25-2010, 10:29 PM
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tex1790
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Default RE: Trouble with Inboard Engine

Long story! I never sent it to CMDI, I sent it to another shop (I would rather not get into it) but long story short after I sent quite a bit of money to this person I was told it was fixed and then I got the motor back the same way I sent it out, in pieces. Sorry I couldnt help you out.
Old 01-25-2010, 11:57 PM
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Default RE: Trouble with Inboard Engine

I went back and read your first posting. I'll try to be nice here. GET RID OF THAT WHITE LIGHTNING! I wouldn't run that stuff in an RC car or truck engine much less a performance engine like your MAC. The oil content is way too low for boat use and sure wouldn't use it for anything more than trying to start a fire. To me the percentage of oil is even too low for the 4-wheelers. They advertise it as helping the engines get up to operating temperature quickly so I'm sure that it's wearing them out also by not providing enough protection.
Lousy fuel and the wrong plug can give you major headaches.

Now back to your pictures. In them the remote needle appears to be plumbed correctly. It also looks like a Kalistratov remote needle that Andy Brown used for his engines. He also used their needle bearings. Turn the black part of the remote needle all the way in then adjust the screw to around 4-1/2 turns out for starters, you may have to go richer.

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