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Loss of RPM @ Wide Open Throttle

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Loss of RPM @ Wide Open Throttle

Post by quitchabitchin » Sun Aug 01, 2010 9:51 pm

We have been fighting this issue for a while now, the boat will start great, run great, plane out, run right up to 3700 RPM's and hold there for a while. Then RPM's will fall off 300-500 like it's starving for fuel. There is plenty of fuel flow in the carb. There is no sign of misfire. When the RPMs drop, water flow out of the exhaust also drops off considerably and more steam comes out. Could this be caused by overheating? And what would cause it? Should I run it without the thermostat? The temperature gauge, which is measured on top of the intake, usually stays slightly under 160 once it is warmed up. If the exhaust gets too hot, i.e. the steam, would it cause a loss of RPMs?
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Post by jfrprops » Mon Aug 02, 2010 10:22 am

That is symptomatic of the Ethonol in my experience.

John from Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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similar challenge!

Post by a_lab_lover » Mon Aug 02, 2010 3:57 pm

:( We had our '71 Lancer 19 in the water for the first time this past weekend. She ran great for about 90 minutes with rpm's ranging from 2500 to 3500. Rather suddenly, I experienced a significant loss of power and the engine stalled. It started right back up but when I tried to increase the throttle in gear, the engine 'bogged down' and I could hear it backfiring several times. The engine rev's fine in neutral. I could only get back to port by keeping the engine barely above idle in gear(~8mph per the gps).

My mechanic noted that the outdrive had a worn bearing (or u-joint?) and suggested that I replace it when I put her up for the winter...but I'm wondering if that might be the problem?

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Post by quitchabitchin » Mon Aug 02, 2010 6:08 pm

I have wondered about ethanol. Does ethanol burn hotter? The tank of fuel in it now is 93 octane from a station without the ethanol warning sticker (10% ethanol) and it ran better the last time out than it did all summer last year. Would ethanol cause it to burn plugs? It had the electrode burnt out of the #3 plug when we purchased it and the previous owner complained of the same symptoms.
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Post by Sugar Shack » Mon Aug 02, 2010 6:15 pm

I am suspicious of the fuel in both cases. In the first if you are overheating the problem would be more evident than the loss of a few hundred RPM. In the case of the Lancer I would first look at your fuel situation. Check your fuel/water separators as you probably are loaded up. The bearing is not the cause of this problem.

Ken

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Post by jfrprops » Mon Aug 02, 2010 6:42 pm

I agree it is not likely the bearing do this...

Ethonol is the WORST, multiple problems...including all the ones you report and more. Not topping out in RPM's, doing that after running OK for a while, all are the symptoms I had in outboards with the ethonol.

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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Post by Paul P » Tue Aug 03, 2010 11:53 am

Ignition advance could be the issue too. If you are running with a 25 degree advance at 3000 for instance, and the motor was supposed to advance all the way to 30 or 32 at tht point, then you are leaving a lot of power on the table.

The fact that the boat will get up on a plane and run well at 3700 suggests ignition advance is not the problem, however, because once it advances to that point, it is unlikely to fall off as you described.

Regards,

Paul
1956 17' CC Sportsman, 300-hp
1957 17' CC Sportsman, 95-hp
1966 20' CC fiberglass Sea Skiff, 210-hp+
1973 23' CC Lancer inboard project, 427/375-hp.
1966 38' CC Commander Express, 427/300-hp(2)

So many boats.........so little time.....but what a way to go!!

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Post by quitchabitchin » Thu Sep 16, 2010 8:58 pm

Here we go...after several outings, checking this, checking that, new fuel, filter, treatment, etc...the boat still ran like crap once it got hot. I decided to rebuild the carb with the help of a friend. As soon as I took it apart, it was apparent what the issue has been all along...both metering rods were broken. One had an attempted solder job (nice try). My first call was to my wife's uncle who has raced Mopars equipped with Carter AVS's and AFB's for many years. He said "Bring it over, I just saw an old strip kit with jets, rods, and springs in the garage the other day." 2 cans of carb cleaner, a few combination comparisons and 45 minutes later, I had a freshly rebuilt carb with slightly larger metering rods and proportianally larger jets. Bolted it on today and took it for a ride...what a difference. The first time I hit it, it jumped out of the water like never before. Aside from a few slight adjustments and tuning, I am very pleased with the results.

The only question I have now is I am still only getting 3600-3800 rpms at WOT. The manual I have says the boat has a redline of 4200 and not to exceed 3600 max. cruising speed. Shouldn't I be able to run 4000-4200 for a short period of time. I think I can get another 1/4 to 1/2 inch of throttle cable with a minor adjustment. Would this get an extra 500 or so rpms or am I pushing it?
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Post by mfine » Fri Sep 17, 2010 6:06 am

The inability to get to 4200 RPM's could be throttle cable adjustment, prop selection, or some other performance/tuning issue. If you have someone else to steer, it is pretty easy to disconnect the throttle cable and operate the throttle by hand.

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Post by Paul P » Fri Nov 04, 2011 9:46 am

mfine wrote:The inability to get to 4200 RPM's could be throttle cable adjustment, prop selection, or some other performance/tuning issue. If you have someone else to steer, it is pretty easy to disconnect the throttle cable and operate the throttle by hand.
I agree totally with the comments, but be extremely careful operating the throttle by hand. You are prone to movements of the throttle that are more abrupt than you would do if it was connected to the system, and you could well throw yourself or someone else out of the boat. Seriously, the voice of experience here, having seen feet in the air and lasagne spread all over my aft deck :-)

good luck,

Paul
1956 17' CC Sportsman, 300-hp
1957 17' CC Sportsman, 95-hp
1966 20' CC fiberglass Sea Skiff, 210-hp+
1973 23' CC Lancer inboard project, 427/375-hp.
1966 38' CC Commander Express, 427/300-hp(2)

So many boats.........so little time.....but what a way to go!!

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Post by mfine » Fri Nov 04, 2011 10:27 am

Never try to debug engine problems while holding a lasagna.

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Post by Paul P » Fri Nov 04, 2011 1:06 pm

Ha ! Right !

I was referring to some other spastic throttle movements I made one day before knowing just how much torque was transmitted through a pair of 2.5:1 gear reductions to 23x25 propellers from a pair of 427 motors. I sort of goosed it I guess, without warning passengers, and I looked back and literally saw somone hanging onto the aft rail like it was an olympic gymnastic competition, feet to the sky, came within a hair of going overboard. I actually think I pulled the throttles back and the person settled back into the boat instead of doing a complete flip out. It would be easy to eject passengers with all that torque.

My caution stands however, lasagne notwithstanding, because being in the engine compartment with fingers on the throttle would potentially result in some very jerky throttle inputs that could not only toss someone around, it could potentially cause some mechanical damage too. Just a word of caution.

Using due care it would be a way to see if the throttles were opening fully, but that can be done at the dock, right? :-)

Your previous comments about "other tuning issues" is a good one, because just with a freshly rebuilt carb there could still be a string of things holding the performance back, like valve settings, ignition timing, plugs, wires, distributor spring advance issues, etc., and of course prop pitch and even the condition of the bottom (the latter a pretty significant impact for cruisers).

best,

Paul
1956 17' CC Sportsman, 300-hp
1957 17' CC Sportsman, 95-hp
1966 20' CC fiberglass Sea Skiff, 210-hp+
1973 23' CC Lancer inboard project, 427/375-hp.
1966 38' CC Commander Express, 427/300-hp(2)

So many boats.........so little time.....but what a way to go!!

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Post by quitchabitchin » Sun Nov 06, 2011 12:08 am

We finally got it dialed in at the Bluegrass Rendevouz ACBS show. I have tried a couple different adjustments with the throttle cable and it seems like we could use another 1/4" of cable. When we get over 4000 RPM's, the engagement point of the transmission is to high and you throw a killer wake at idle. This is not cool in the marinas. I adjusted it back and it runs right at 4000 RPM's at right around 40 MPH.

The weekend after the show, I was getting ready to go to Norris Lake in TN and checked the oil during the pre trip inspection and it looked like a milkshake, full of water. The dipstick is not overly full, so it is not taking on a bunch of water, just enough to emulsify the oil. I took both exhaust manifolds off tonight and will plug the water intake and fill them with water tomorrow and see if water is leaking back into the cylinders through an open exhaust valve when the engine is shut off from an internal crack in a manifold. If they both test good, I guess the intake is next.
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Post by mfine » Sun Nov 06, 2011 4:46 pm

Be REAL careful starting that engine. A little water in the wrong cylinder when it fires will turn into a complete rebuild job.

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Post by quitchabitchin » Sun Nov 06, 2011 9:04 pm

Bad news. I pulled and tested both exhaust manifolds and both tested good. Then I pulled the intake and found a nasty weld about 12 inches long on the bottom of the intake. I will have it pressure tested to make sure it is holding. While looking over the rest of the engine under the intake, I noticed a small crack in the block on the hump outside of the #6 cylinder. It is about 2-3 inches long and hopefully can be repaired. I am waiting on a couple folks to look at it and see if they can weld it. It looks like the whole thing is going to probably come out and be rebuilt from top to bottom. Judging by the two welds on the bottom of one riser, the weld on the intake, and the crack in the block, it looks like someone didn't winterize this engine at some point in it's 42 years on the planet. We'll see what happens.
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Post by jfrprops » Sun Nov 06, 2011 9:34 pm

I have a 327 RH I think it is RH...) short block (I THINK....in storage for long time) was a NAPA rebuild, then never reinstalled in a cruiser that was cut up. Will check if you are in need. I will never use it.
John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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Post by quitchabitchin » Sun Nov 06, 2011 10:34 pm

Thanks John. I will see what transpires over the next week or so. I talked to one friend who says he has a guy that should be able to fix it. I will probably have to strip the block and have it tested to see how bad the crack is once it is all cleaned up. I will let you know.
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Post by quitchabitchin » Wed Nov 09, 2011 6:04 pm

It looks like this engine is toast. The cost of fixing this block is just not worth it. The crack is in a bad spot. It is right below a head bolt which will pull on the block constantly.
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Post by mfine » Wed Nov 09, 2011 6:32 pm

You should be able to find plenty of 350 blocks that will make a fine motor, and hopefully you can be back in the water by spring.

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Post by quitchabitchin » Wed Nov 09, 2011 9:07 pm

This is probably going to turn into a full blown restoration, with a small twist. More of a resto-mod style if your familiar with this style of muscle/classic cars. The biggest problem with a back to original restoration is the red nautolex flooring is shot and there is none to be found anywhere, so we are going a slightly different direction on the interior with the original exterior.
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Post by mfine » Thu Nov 10, 2011 9:48 am

If it is not going to be orig, you can modernize the engine a bit. A slightly aggressive 350 at 300 hp or so should give you a little extra out of the hole and at top end. Replace the nautolex with some shag carpet, hang some fuzzy dice from the mirror and you will be well on your way.

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Post by quitchabitchin » Thu Nov 10, 2011 11:10 pm

Shag carpet would stink, literally. We're thinking more of the Lancer GT Concept style. See the images on Google.
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Post by mfine » Thu Nov 10, 2011 11:16 pm

I was kidding about the shag, although I have seen it in more than one boat from the 70's.

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Post by Paul P » Tue Nov 15, 2011 11:32 am

I'm not a shag carpet fan, however it was installed on numerous Commander models "back when", and it is even noted as a feature on some of the old literature. Times have changed :roll:

regards,

Paul
1956 17' CC Sportsman, 300-hp
1957 17' CC Sportsman, 95-hp
1966 20' CC fiberglass Sea Skiff, 210-hp+
1973 23' CC Lancer inboard project, 427/375-hp.
1966 38' CC Commander Express, 427/300-hp(2)

So many boats.........so little time.....but what a way to go!!

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Post by quitchabitchin » Tue Nov 15, 2011 9:27 pm

It turns out that the water in the oil was the engine's way of saying "replace me". I pulled the heads and after who knows how many years of running lean because of the broken metering rods in the carb, the #2 piston was melted down to the rings. It was still running very good when I found the water in the oil and it is amazing that this piston was melted. I'm not sure if it is just the top and still holding some, probably not all, compression and still making power. I can see the first and second rings. Good news is that we will be able to use the engine John in Virginia (jfrprops) has stored in his basement. I have to say, while I haven't formally met him yet, but John is a class act and I appreciate his help in this matter. I will be travelling to Va. to pick up the motor sometime this fall/winter, time and weather permitting. Meanwhile, the current motor and trans are ready to come out as soon as I can get it under the hoist and all the hardware and interior is coming out for a full paint job and new interior. I can't wait for the finished product.
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Post by jfrprops » Tue Nov 15, 2011 9:45 pm

Ready when you are.....sorry that one melted down...

John in Va.
1980 Fairchild Scout 30
19?? custom Argentine Runabout 16'
1954 Whirlwind deluxe dual ckpt 16'
1921 Old Town Charles River 17' (founding Captain, James River Batteau Festival)

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Post by quitchabitchin » Tue Nov 15, 2011 10:27 pm

Thanks John. As bad as it sucks, it's just the old girl's way of saying "quit messing around and make me sexy again." It's one of those things that you know are coming and you put it off until something forces the issue, in this case the water in the oil forced an investigation and look what we found. It's better to find out in the garage than out on the lake with a couple of kids and the wives baking in the sun with no way back to shore.
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Post by decsdad » Mon Nov 21, 2011 10:33 pm

sorry about the news but it sounds like you have the right attitude. i'm no pro, but figured i'ld chime in, having the same red nautilex issue. same boat only a '70. as i pulled out the carpet, i was pleasantly surprised that the side hulls and foot rest still had the nautilex and was in great shape. not so lucky with the floor. i decided to try a cheap route and love the result.
home depot sells a product called "deck restore". it comes with a mesh roller and goes on wavey and thick. 2 cans per box (@$40) and i was able to get 2 coats out of that. (don't apply to newer wood, it's designed for older, weathered wood.)
it feels great under bare feet if you use the roller and not a brush and i couldn't be happier...well check that, the only complaint is the limitation of color choice. i believe i went with 'navaho red' (?) and it is a shade dark. still looks good, feels great, and was affordable.
this reminds me to get some pics posted... hopefully soon.
good luck with the project

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