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Alpha I leg stealing power?

S

scheffer

New member
I have a 2005 Bayliner 245 with Mercruiser 5.0L and Alpha I drive. There was a small gear oil leak so my mechanic recently removed the leg and replaced the gaskets to stop the leak. Now the boat seems to have lost power. Before, the gasket replacement, I could easily plane with the engine at 3100-3300RPM. Now if I try to run in the same RPM range, the boat falls off the plane. To stay on the plane I have to run the engine at ~3800RPM.

There was no work done on the engine, so it seems like the power loss must be coming from the leg. But the only change made was to seal up the interface between the transom mount and the lower leg with new gaskets. The lower leg wasn't opened up.
 
Hi guyjg,

It's my prop. The same one that I was using successfully before the gasket change. There was no change to gearing either.
 
I doubt the gasket work caused the power loss. Tach. may be out of calibration. Is the engine carbed or EFI? First look for a loose spark plug wire. When was the basic engine service performed...new plugs, fuel filters, etc? Did you get a tank of bad fuel recently?
 
Double checked and yes, the leg is there... whew. Dodged that bullet.

The engine is carbed. How would I check that the tach is out? It _seemed_ fine before the leg service. Tune up was performed approximately 10 hours ago. Full service was done: new plugs, filters, etc.

The bad gas seems like a very possible source. I filled up 10min after they did the leg maintenance from a marina I don't usually use. If it was bad gas is there an easy way to diagnose? Do I just need to run through the tank? Can I add something to salvage the $200 in gas (fuel is ridiculously expensive these days)?

Thanks for all your help/suggestions,
karl
 
pull the fuel / water sep. filter, dump it into a jar and see what you have. do you treat the fuel at fill ups? ( add sta-bil etc.)
 
I hadn't been treating it at fill-up, was going to do that for winter. If there is water in the fuel/water filter, then what?

Could this just be a lower octane issue?
 
Ayuh,.... Bad gas will cause a loss of rpms...
It Won't cause a hull to fall off plane at the same rpms it used to plane at....

Is there any bottom growth,..??
Is the trailer still under it,..??
 
Bottom is clean, it was cleaned about a month ago. There is no growth whatsoever. I don't have a trailer, the boat is moored at the local marina.

When you say bad gas will cause a loss of RPMs, do you mean it will just affect the highest RPM possible? Why wouldn't bad gas affect the power at a given RPM? What if it was happend to be lower octane?

Thanks,
karl
 
Something is not right here. A Bayliner 245 is not a heavy boat and if I`m not mistaken, the 5 litre in 2005 was rated a 260 hp which is same as older 5.7. Should get that boat on plane with no problem. If it is taking considerably more rpm to get it on plane, then something has to be slipping or leg is trimmed too high or tach is simply gone wonkie. . Fact is, his symptons aren`t power loss as much as asking why the motor APPEARS to be reving higher to do the same job. Better question to ask might be what SPEED he used to plane at and what speed he needs now.
 
I am no boat mechanic and what the rest are saying is probably correct, but does the boat have trim tabs and are they working properly? also I would get a calibrated shop tach and make sure your rps's are right.

I use a mix of marine sta-bil and startron for fuel treatment every fill up and that works for me.
 
If you are using the trim position gauge to trim the OD while underway to get onto plane it may be out of adjustment. It is a simple adjustment to recalibrate it. Lower the OD until it bottoms out. Loosen the trim position sender hold down screws and rotate the puck left/right until the gauge aligns w/the DOWN indication mark/line. Tighten the screws and you are done.

I only used the gauge when I was starting the engine or entering shallow water. I used my hearing to listen to the engine RPMs in relation to what the boat was doing when planing and adjusted trim to achieve optimum cruising speed per RPMs.
 
Agreed the boat is not heavy. Everything I've read rates the 5.0L horsepower at 220.

Trim tabs and leg trim are all working correctly. I tried adjusting the trim in many different ways (leg up/down combined with tabs up/down) but it didn't make a noticable difference. If the RPM is below ~3800RPM, the boat falls off the plane. I found this same behavior before I started having the problems. The trim affected the position of the boat on the plane and made a difference to the speed a bit, but wouldn't affect the ability to plane at a certain RPM. I generally follow guyjg's advice/procedure

guyjg said:
I only used the gauge when I was starting the engine or entering shallow water. I used my hearing to listen to the engine RPMs in relation to what the boat was doing when planing and adjusted trim to achieve optimum cruising speed per RPMs.
Click to expand...

Generally, the minimum planing speed for my boat is somewhere between 19 and 21 knots (depending on load and fine tuning of RPM). This is consistant before and after the higher RPM problem started.

So, it seems there are a number of possibilities I should investigate:
1) tach is out of whack
2) bad gas
- water in gas, check seperator
- still not sure if this could be a low octane problem
3) loose spark plug

Did I miss anything? Any more ideas?

This is great everyone, thanks again for your thoughts.
 
sheffer said:
Before, the gasket replacement, I could easily plane with the engine at 3100-3300RPM. Now if I try to run in the same RPM range, the boat falls off the plane. To stay on the plane I have to run the engine at ~3800RPM.
Click to expand...

bondo said:
Ayuh,.... Bad gas will cause a loss of rpms...
It Won't cause a hull to fall off plane at the same rpms it used to plane at.
Click to expand...
Yes.... I agree!

My initial thoughts were, that given all else is "Un-Changed", that this reeks of a propeller change, or a final drive ratio change (either in a pitch down, or a lower ratio).
Any of us could re-create this scenario by doing one or the other, and without touching the engine or the hull bottom.

Sump'n aint quite right here!

.
 
RicardoMarine said:
Yes.... I agree!

My initial thoughts were, that given all else is "Un-Changed", that this reeks of a propeller change, or a final drive ratio change (either in a pitch down, or a lower ratio).
Any of us could re-create this scenario by doing one or the other, and without touching the engine or the hull bottom.

Sump'n aint quite right here!

.
Click to expand...

I agree. Sounds like they did not reinstall his original drive.
 
They put back my original leg, guaranteed. I was present for the entire maintenance. I watched the guy take the leg off, I watched him put it back on. The leg was never more than 5ft away from my boat and there were no other legs within 100yrds of where the work was performed... We did the maintenance right on the marina lift next to the ramp...
 
If the mechanic didn't seal up the interface between the "transom part of the leg" and the "lower leg" properly (sorry I'm not familiar with the right jargon, the open area with the 2 universal joints)... could water be getting in there and reaking havoc? Would this cause a loss of power?
 
Then you may have a dirty hull that is now requiring additional RPM to get and keep you up on step.
Not too much else makes any sense, IMO.
 
The boat bottom was thoroughly cleaned just over 1 month ago. While the boat was on the lift for the leg "repair" I checked out the bottom. There is zero growth.
 
The only thing that would appear to make any sense, would be that somehow the tachometer is now not reading correctly.
Like suggested earlier, any engine related issue, would not necessarily show up like this.
RPM is RPM.... what the engine is turning, is still reduced by the same reduction to the propeller.

Could the prop have become damaged during this?
 
Here is a list posted to this website, by Chief Alen:

List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

Above copied nd pasted from another website Don s is the author.
 
Scheffer.
As the experts here have said, you have some checking to do. But I would like to add. Take a marker and hold it on the lower unit at the tip of one blade. Rotate to the rest of the blades and see if they all are the same. Sounds like one blade was altered by miss handleing during the service.
I would like to add. That boat planes faster, saves fuel with a SE hrydrofoil. No loss of top end speed. You can see over the bow 5 mph sooner and stay on plane at lower speeds. My boat would fall off plane like a rock untill I installed one. Now the handleing is much more forgiving. They don't cost much and pay for themself real fast. Got to be the biggest bang for the buck in boating.
Moondrifter
 
RicardoMarine said:
Could the prop have become damaged during this?
Click to expand...

Hi Ricardo, When the leg was off, it was just resting on the pavement. There was no noticable difference in the prop condition before and after the leg repair. How much damage would need to be done to make a difference like this? Seems like it would need to be fairly significant...


ALL:
One important point I forgot to mention is the sequence of events leading up to what seems to me is a simple loss of power.
1) Tuesday morning I motored from my marina to the marina with the lift approx 1/2 hour away. No problem planing, boat performed as always
2) Boat went on lift, mechanic did work, boat back in water. During this time, we didn't even open the engine compartment so unlikely anything changed in there due to work
3) Took boat to fuel dock which is about 10min further from home marina, filled up. Tank was only 1/4 full when I pulled up, so I got about 40 gallons of gas in the fill up (60 gallon tank). No problem planing to the fuel dock. Note that I have never bought gas here before.
4) Motored back to home marina (~45min) still no problem planing. I can't remember how fast I was going here exactly. I might have been running a bit higher RPMs than normal since I was running late by this time.
5) 5 days later on Sunday, took the boat out with family, noticed problem planing.

I really think this sequence excludes a problem with the prop/gearing/bottom. Otherwise, I would've had problems planing immediately after the mechanic did his work. In my mind, it also points strongly toward the quality of the fuel I got from the different fuel outlet.

What is the effect of old gas (or low octane) on engine performance?
Would it cause the motor to have less power/torque at a particular RPM? If not, what effect does it have on engine performance?
Any idea how long would it take the old/bad gas to filter into the engine and start causing problems?
If water were in the gas, would it take longer to see the effect due to mixing and/or separation and/or clogging the water separator filter?

One final note: I never tried to see what my WOT RPMs are. Neither before or after my problem started, so I can't really use that as part of the diagnosis.

thanks again...
 
hook up an aux. fuel tank with fresh gas and go for a ride, that will tell you if its fuel related, I would take a shop tach with me also.
 
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