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  1. #1

    Default Desperate for Mechanical Insight

    Hi group,
    I'm in a world of trouble and I desperately need some advice. After attempting to call the only Moomba mechanic (the only one within two-plus hours of my house) for over *two months*, I finally had to resort to using a conventional mechanic who is very familiar with the Chevy 350, in hopes fixing my Moomba's Indmar 350 Carb engine. That went very badly and now I'm stuck with a new engine that doesn't work - not sure what to do next.

    Some background: After I purchased a 2000 Kanga w/94 hours, my engine overheated in *less* than an hour. It appeared that something may have been stuck in the cooling system, but it was too late once I realized it was running over it's heat threshold. I wound up with water in the oil, etc (cracks heads from what I understand). I immediately called the local Moomba tech, no return call ... Local Indmar techs - two disconnected lines, one (MasterCraft specialists) didn't call back.

    My only option was to try a conventional automobile mechanic who did a lot of work with similar engines. He purchased a new Chevy 350 Vortec that according to him is identical to the Indmar (as far as the basic block/heads that he was using), then he used all of the existing marine parts from the Indmar to outfit the engine.

    When all of this was done, the engine seemed to run fine (out of the water at least) -- just one problem. To this day, I can't get the engine over 3,600 - 4,000 RPM (depending on the day). I attempted to take the engine back to him on four separate occasions and he swears up-and-down it runs perfect. Without a load (out of the water), we've rev'ed it over 5,000 without a problem, every time. Yet as soon as the boat hits the water, I cannot get any top-end. Wondering if it wasn't able to push the shaft, I attempted to align the shaft to the .002 required by Moomba; however, that didn't give me any added speed. The prop and all other parts are the same parts that worked great on the original engine. After reading this forum, I had him set the timing to 10 BTDC @ 850 RPM as recommended here for more WOT -- but this didn't help. He checked/adjusted the carb several times, but he claims it's running fine.

    I've spent literally weeks trying to comb this forum for something that might give me an idea -- but I can't find anything similar to my circumstance.

    Unfortunately, I'm not mechanically inclined and I have a new Moomba I purchased that I have yet to be able to use for fear I may be jeopordizing the engine in the present running condition. Most recently, the mechanic doesn't want to work on the boat because he swears it runs fine. Essentially I'm stuck with a very large, pretty paperweight.

    My question is two fold: One, does anyone have *any* idea what the problem might be -- why I can't get more than 4,000 RPM on a good day - from a new engine ... Two, does anyone have a recommendation for a marine mechanic somewhere near West Palm Beach, Florida?

    Thank you in advance for *ANY* suggestions!
    -Rusten

  2. #2
    Join Date
    Aug 2004
    Posts
    7

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Rusten,

    I'm not going to pretend that I have the answer but....... in order for an engine to run it needs compression, spark, fuel and air. If these four things are present in correct supply it will run.
    I'm sure you've tried everything. However in going over your story you said that you were able to get 5000 rpm at the shop but not on the water...right? I'm wondering if there was any difference between how this was done? For example I have a strong hunch that the engine cover was open when the mechanic got the 5000 rpm.....but on the water the cover is normally down. If this is true it sounds like the engine is starving for air. Check the carburetor and make sure the butterfly valve is wide open at full throttle. Also check to make sure that nothing is blocking the air intake vents on the engine housing. The lack of air would cause the symptoms you have experienced.

    As for timing you can always try advancing or retarding the timing to see if that helps but it sounds like you've already tried that.

    good luck
    Jerensen

  3. #3

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Hi Jerensen,
    Thanks so much for the reply.

    I think I explained the problem incorrectly. I don't believe the difference is a running condition/change, but that the engine can't get up over 3,500-4,000 RPM when there is a *load* applied (when it's pushing through the water as opposed to out-of-gear). In other words, I can take it out-of-gear and run it over 5,000 RPM when in the water -- I just can't get it to rev when actually pushing the prop. This is why I thought it may be an alignment issue and I spent some time making sure the alignment is 100%. I can hand-turn the prop very easily, so I don't think that is stopping it.

    It runs at exactly 160 degrees at all times, oil pressure at about 70 psi when it gets going in the 3,500 RPM range.

    I think the engine probably gets air okay. I've been testing it with the entire engine case/back panel removed. If I understood what could make an engine rev fine, but not push a load, then I might have a better idea - but the mechanic says that could be anything and he doesn't want to work with it again. I've read up on changing carburators -- if I can't find someone to fix the boat, I may just try to add a new carburator on my own, even though the mechanic says it won't do anything.

    I wonder if any Indmar mechanics in Florida might have those computer diagnostic systems -- perhaps that would help get to the bottom of the problem.

    Thanks again for your suggestions,
    -Rusten

  4. #4
    Join Date
    May 2003
    Location
    south east michigan
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    241

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Did the mech. change the cam,and/or intake manifold when he changed engines?
    jy

  5. #5

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Hi James,
    Thank you for the reply.

    The mechanic utilized the cam shaft included with the new 350 Vortec (non marine) engine, which as I understand is slightly different from the "Marine" version of this same engine. I asked the mechanic if this could be related to the current problem. He explained that this could not be the cause of more than 300 RPM difference, maximum, in his opinion. He said that if we were comparing a non-Marine Chevy 350 alone to the Marine 350 Vortec, it would be a significant difference; however, the difference between a non-Marine 350 *with* Vortec heads as a "Crate" engine that is a higher performance specimen, this is an insignificant difference in comparison to the Marine version. Do you have any evidence to help me explain that he is misguided in his thinking / possibly get him to install the cam from my original Indmar 350?

    I am going to ask him about the Intake Manifold tomorrow. He used just about everything from the Indmar outside of the block/heads, so I'm guessing the Intake Manifold is the original from the Indmar. Can you help me understand the significance of this / the issues if this was/was not replaced?

    Thanks so much,
    -Rusten

  6. #6
    Join Date
    Apr 2003
    Location
    Powhatan, VA
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    316

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Can you get indmar on the phone and ask them to define some of the differences?

    They may go deeper than you think. The automobile engine may be designed to redline at 4000 rpm or so.... there should be a dyno curve available for the crate engine that would define the horsepower / torque / rpm curve.

    I'm very surprised about the heads being the same. I also thought the main and connecting rod bearings were toleranced differently on the marine engine, for different lubrication characteristics. The car engine uses 5 W oil, the marine version uses 20 W oil. If you are using 20 W in this crate engine, and its not toleranced for it, you may be starving for lubrication and compression at top end.... you really have got to find somebody that knows what indmar does inside these motors.

    The marine service for a motor is considered to be extremely stressful, far more stressful on a motor than the typical automotive application... that's why I think indmar bullet-proofs the lower-end internals....again, you need to check. The parts guy at my dealer said the indmar is close to the auto crate motor, but on cross examination he has absolutely now experience or data to make that claim. Plus, he's wrong 85% of the time about Moomba parts. Frustrating, but unfortunately par for the course in the marine retail world.

    I'm also surprised you'd ever rev the engine that high. Have never had our Outback above 4500 and rarely above 4200. Its a ski boat, designed for about 40mph top speed, and can go for many outings, many days, not exceeding 35 mph or roughly 3800 rpm.

    So, check those expectations that you have about performance. Be cautious on the top end. Dangerous place to be messing around.

  7. #7
    Join Date
    Apr 2003
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    Powhatan, VA
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    316

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Camshaft and intake ... yes, that could definitely be a difference. Should be able to ( very carefully ) remove the marine camshaft, get a part number, get a part number from the specifications on the crate motor, and compare the camshafts. Should be able to find performance curves on each of them also.

    Just be sure to let us all know what you find. This whole topic is an area a lot of us have wondered about.

    Indmar internal information seems hard to come by, maybe they try to keep the internal specifications "trade secret" in order to protect their niche. The last thing they want is marine engines replaced with less expensive crate engines. The key is figuring out what they have optimized internally in the marine engine over the years. Again, dig deep here. You may have to call big boat places on the coast to get real marine mechanics. Surely you could go down a phone list and eventually find somebody experience.

    I can't believe this topic hasn't been searched out before in a google search....

  8. #8
    Join Date
    Apr 2003
    Location
    Powhatan, VA
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    316

    Default Replying to Topic 'Desperate for Mechanical Insight'

    http://www.marine-engines.net/topics/001183.html?motors

    Here's one link that gives general reference to cams and heads.

    No mention at all of engine internals...

  9. #9
    Join Date
    Apr 2003
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    Powhatan, VA
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    Default Replying to Topic 'Desperate for Mechanical Insight'

    4th post. Sorry, can't edit others to add stuff.

    OK. Its 4:30 in morning and I've been researching on the net for 2 hours.

    According to what I'm reading ( and its mostly all third party stuff ), the marine application requires a motor rated for continuous duty. A totally different service factor than automotive. They are designed with higher quality pistons forged and/or with high silicone content that don't expand as much with heat build-up, different internal tolerances, very different cams and heads.

    Basically, the marine version is an engine with parts that are heavy duty, similar to the way you would build a hot rod motor, to allow wide open throttle WOT, allow tolerances to remain proper for oiling while heat builds up, and generally to have a very, very different torque curve.

    The automotive application is comparitively light-duty. Not a continuous service factor.

    If you selected a truck-version of the automotive crate motor, you may be in better shape, especially as you change the cam. Truck motors are supposedly more robust, but apparently not so robust as a marine motor.

    No matter what, unless you've bought a special duty, bulletproof crate motor, running at high rpm is going to be dangerous. And continuous full power starts, like needed for slalom, are going to take their toll.

    Pratically speaking, trying to salvage some boating season, remaining questions are can you find a way to baby the thing and still have fun and how long will the motor it last. 1 year? 3?

  10. #10

    Default Replying to Topic 'Desperate for Mechanical Insight'

    Prior to writing this reply, if anyone else has ANY suggestions -- please let us know. Despite the depth and value of this thread, I still don't have anything to put my finger on the prolem. This post discusses the finer points between two engines, however, I'm still left without an idea of what could cause my 350 Vortec to run at 4,000 RPM (or less) under load when it runs perfectly fine at 5,000 RPM out-of-gear.

    First, to James-
    Yes, the Intake Manifold (which is branded w/Indmar logo) is the same as the Indmar, attached to the new block. The carbs, water pump, ignition system, harmonic balancer, etc (essentially all "marine" upgraded parts on the engine) remain the original parts from Indmar. The mechanic says he only replaced the block/heads with the new Chevy 350 Vortec.

    Hi Catdog-
    Thanks for all of your replies. You've always been a great help when I've had questions on the forum. I've included answers to all of your points; however, consider that I am a software developer and not mechanically inclined. This is a disclaimer I may be way off .

    Regarding the top-end speed, consider that 4,000 is the *MAX* I can ever run the engine as it sits -- and often it won't run over 3,500. Typically it runs at 4,000 for two minutes, then makes a bogging sound and drops to 3,500. I am primarily a slalom skier, running the boat at 3,600-3,900 through the course and presently, the boat won't offer this power. On the same note, I'm *not* worried about running the boat at high speeds, such as 5,000 RPM - not at all. I'm far more worried about why the boat is running so much slower and whether this means that I'm hurting the engine by running it at all. I am so worried about this that I will not run the boat for more than five minutes -- I *only* run it for testing purposes. I haven't skied once since March -- when I sold my former boat and bought the Moomba.

    First - regarding the differences between the marine/conventional "crate" engines: I did a lot of research after my mechanic purchased the non-marine engine despite my requesting him to purchase the marine version at MichiganMotorz or Discount Marine (both have very good pricing on Indmar replacement 350 Vortec marine engines). I was furious when I found out he purchased the standard engine, but the more research I did -- not to mention the fact that I couldn't get a marine mechanic to call me back and he was my only option -- I decided not to make a big deal of his action. In my research I found the same link you mentioned, plus many definitive "features" lists for marine engines. After speaking to Michigan Motors for about 20 minutes, I received a complete overview of differences -- and from what they explained, the cam is about the only significant/operational difference operationally speaking, unrelated to corrosion prevention/etc. At the end of this post, I'll list the full set of upgrades included with the marine version of the engine. Despite the cam and other less significant differences, the core engine appears to be 100% identical. They both have the same RPM top-end (both rated 330HP at 5,000 RPM - at the crank), etc.

    Regarding the performance curve of the marine v. conventional cam for a 350 engine, I cannot locate that data. I also cannot determine what specifically is different between the two camshafts. I do believe they are both hydraulic roller cams (although not being mechanically inclined, this doesn't mean much to me) - and that is the extent of what I can find. The specs for the OEM motor that Indmar builds from are located on GM's site from what I understand. The PDF is here: http://www.gm.com/automotive/gmpower...0_brochure.pdf

    This may not be correct; however, I did find two specifications that may hold true:
    Marine Cam: Lift .474 I, .474 E. Duration @ .050: 210 I, 214 E
    Standrd Cam: Lift .435 I, .460 E. Duration @ .050: 212 I, 222 E

    Regarding the difference in oil - if I understand correctly, the lower viscosity is the minimum, in other words, the number of viscosity while running cold while the higher number is at "operating temperature". Since the thermostat keeps the engine running at 160, the oil is always at the operating temperature viscosity (e.g. on a 20w-40, the oil would run at 40 and the 20 is a moot specification). In short, if I run a 20w-40 or a 5w-40, the engine would effectively be running the same weight at 160 degrees, regardless of which I used. Of course I could be wrong.

    Regarding the two engines being engineered with different qualities of steel/forging/etc -- although I am not experienced in this, the facts appear to speak differently that what you've suggested. None of the documentation or feature-lists for the Marine engines includes such data. The marine engines have better paint, some brass parts, etc. Other than those minor differences, plus the more substantial upgrades in camshaft and intake manifolds (which is preserved from my original engine, so this shouldn't be an issue), there is never anything in black-and-white backing up the claim of a different engine. From what I understand they are made from the same parts/same facility in Mexico.

    --- NEW TOPIC / POTENTIAL IDEA ---
    All of this does raise one interesting point. Indmar's website says that timing cannot be set using "conventional" methods. Does anyone know what it cannot be set using conventional timing methods? I ask because I'm fairly sure this is how my timing was set, with a conventional timing gun on the first plug (did I say that correctly?). Additionally, it appears that cams have to be adjusted in relation to timing/etc. Could this be an issue relating to a unique method required to time the engine and/or a cam adjustment?

    Thanks again for all of your suggestions,
    -Rusten

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