lacking power all of a sudden...here are the syptoms

[reimelss]

So I put a mid 90's model merc 350 into my 1986 Century this past off season. The season before i put a new outdrive SEI 106 1:47 ratio. Things seemed to be doing great...the boat was moving at a nice speed up on plane, i went on a few rides, some rides had to many people on the boat and it could not get up on plane. But when ever the people got off the boat went right back up on plane and was fine.
The boat has always seemd heavy (i have to check the foam to see if tis saturated, but that is another topic)

I went down in prop to raise the RPMs and the boat had even more spunk and a better hole shot. then after a little while it just seemed to get worse.
The engine just started sounding like it was working very hard, it got loud and we lost a lot of power...we couldn't even get up on plane with 2 people in it.
So here is what i have noticed...I am not sure if any of this stuff plays into the problem, but i figure ill list everything.

1. The RPMs were up about 4600 at WOT and now are at like 4k.
2. Engine sounds loud, like its working very hard
3. Oil is clean and full, not gray
4. temperature on gauge looks good around 140-160 range
5. oil pressure is about 40-50 lbs
6. there is a lot of belt dust on the bilge floor
7. when i turn the key to off position the engine seems like it has trouble shutting off, it sputters for a couple seconds and then makes a poof sound
8. there is a little white smoke every once and a while coming out of the riser...not much at all
9. The engine was a rebuild and was in great condition.
10. the compression was good when i purchased

Not sure whats going on here.
I figured id do a compression test.
but if the compression is good then what else could it be? belt dust in the carb?

Thanks for the help!

 

[sethjon]

Re: lacking power all of a sudden...here are the syptoms

Could be too rich. Adjust the carb and see if that helps. What type of ignition do you have? If pts. adjust them too or maybe replace them.

 

[reimelss]

Re: lacking power all of a sudden...here are the syptoms

Could be too rich. Adjust the carb and see if that helps. What type of ignition do you have? If pts. adjust them too or maybe replace them.

I dont think its pts...im pretty sure its thunder bolt...not 100% though

 

[Bondo]

Re: lacking power all of a sudden...here are the syptoms

1)The RPMs were up about 4600 at WOT and now are at like 4k.
2) Engine sounds loud, like its working very hard
3) Oil is clean and full, not gray
4) temperature on gauge looks good around 140-160 range
5) oil pressure is about 40-50 lbs
6) there is a lot of belt dust on the bilge floor
7) when i turn the key to off position the engine seems like it has trouble shutting off, it sputters for a couple seconds and then makes a poof sound
8) there is a little white smoke every once and a while coming out of the riser...not much at all
9) The engine was a rebuild and was in great condition.
10) the compression was good when i purchased

Ayuh,...
1) it's down on power,.. Tune it up...
2) This is probably related to 8),... Fix the exhaust leak...
6) Rusty pulleys,..?? clean 'em,+ paint 'em...
7) probably related to 1),... Again, a Full,+ Complete Tune Up...
10) how long ago was that,..?? that was then, what's the answer Now,..??
Include the compression test with the Tune Up,+ Service...

 

[reimelss]

Re: lacking power all of a sudden...here are the syptoms

Thanks Bondo,
Just to clarify:
2) This is probably related to 8),... Fix the exhaust leak...
How do i go about this? is there a gasket between the risers and manifolds that need to be replaced?...also the top of the risers are very hot to the ouch is that normal?

7) probably related to 1),... Again, a Full,+ Complete Tune Up...
Plugs, wires...what else..i dont want to miss anything and i know plugs and wires cant even be considered a tune up?

10) how long ago was that,..?? that was then, what's the answer Now,..??
Include the compression test with the Tune Up,+ Service...
Im will do the comp test tomorrow am...and will report the numbers then.

 

[reimelss]

Re: lacking power all of a sudden...here are the syptoms

I forgot to mention that i have barnacles on the bottom of the boat..which are getting scrapped tomorrow...but i dont think that has anything to do with the loss of ppower

 

[jtmarten]

Re: lacking power all of a sudden...here are the syptoms

I forgot to mention that i have barnacles on the bottom of the boat..which are getting scrapped tomorrow...but i dont think that has anything to do with the loss of ppower

DING DING DING, I think we have a winner. Before tearing it all apart and replacing parts, try it after the hull is clean.

 

[Doernuth]

Re: lacking power all of a sudden...here are the syptoms

What is the source of the belt dust? Make sure you dont have an accessory that is stuck or a belt slipping. Clean the pulleys. Check belt tension.

Barnacles can make a HUGE difference in performance. make sure they aren't blocking the water intakes on the drive also. Your temp is good but you didn't indicate what type of cooling you have.

Tune up should include at the minimum, plugs, wires, cap, rotor, adjust points (if equipped), timing, check/change all fluids and filters, esp the fuel filter and grease/lube everything you can find.

 

[fishinpa]

Re: lacking power all of a sudden...here are the syptoms

What is the source of the belt dust? Make sure you dont have an accessory that is stuck or a belt slipping. Clean the pulleys. Check belt tension.

Barnacles can make a HUGE difference in performance. make sure they aren't blocking the water intakes on the drive also. Your temp is good but you didn't indicate what type of cooling you have.

Tune up should include at the minimum, plugs, wires, cap, rotor, adjust points (if equipped), timing, check/change all fluids and filters, esp the fuel filter and grease/lube everything you can find.

Yeah what say we just replace points if equipped / part of a tune up ,guessing or they -Look Good - generally isnt much help in tuning ..


fish

 

[reimelss]

Re: lacking power all of a sudden...here are the syptoms

What is the source of the belt dust? Make sure you dont have an accessory that is stuck or a belt slipping. Clean the pulleys. Check belt tension.

Barnacles can make a HUGE difference in performance. make sure they aren't blocking the water intakes on the drive also. Your temp is good but you didn't indicate what type of cooling you have.

Tune up should include at the minimum, plugs, wires, cap, rotor, adjust points (if equipped), timing, check/change all fluids and filters, esp the fuel filter and grease/lube everything you can find.

Its raw water cooled, not a closed system.

Would barnacles have an effect on RPM range though?

 

[aktrucker]

Re: lacking power all of a sudden...here are the syptoms

Thanks Bondo,
Just to clarify:
2) This is probably related to 8),... Fix the exhaust leak...
How do i go about this? is there a gasket between the risers and manifolds that need to be replaced?...also the top of the risers are very hot to the ouch is that normal?

Yes, there is a gasket between the risor and manifold. How hot is VERY HOT, I can hold my hands on mine at full temp, can you? I have a closed system, but I would think the risors should still be WARM, not HOT on a raw cooled engine...correct? Sounds to me like you have a water circulation issue, or plugged manifold/risor.

The problem you have stated as getting worse.....what is the time-frame here, if it's only a difference of a few weeks, there wouldn't have been enough barnacles attaching in that time to make that drastic of a change, but yes, get the hull cleaned.

 

[aktrucker]

Re: lacking power all of a sudden...here are the syptoms

Also, if you have a LOT of belt dust you should pull the flame arrestor and clean it. It is amazing how much belt dust will screw with air intakes (I know this more from my snowmachine than my boat, but air intake is air intake).

 

[Doernuth]

Re: lacking power all of a sudden...here are the syptoms

Yeah what say we just replace points if equipped / part of a tune up ,guessing or they -Look Good - generally isnt much help in tuning ..


fish

Ok fish you got me, replace the points, preferably with electronics. Points are a pain in the _______!

Yes anything that effects water flow will change the hydrodynamic pressure on the prop and can cause the rpm drop. It could also be a fuel problem if the engine isn't getting proper fuel pressure it can bog down. Clogged filters, fuel intakes, tank vent or bad fuel lines can cause these issues as well.

Eliminate one problem at a time untill you get the right one.

 

[reimelss]

Re: lacking power all of a sudden...here are the syptoms

Yes, there is a gasket between the risor and manifold. How hot is VERY HOT, I can hold my hands on mine at full temp, can you? I have a closed system, but I would think the risors should still be WARM, not HOT on a raw cooled engine...correct? Sounds to me like you have a water circulation issue, or plugged manifold/risor.

The problem you have stated as getting worse.....what is the time-frame here, if it's only a difference of a few weeks, there wouldn't have been enough barnacles attaching in that time to make that drastic of a change, but yes, get the hull cleaned.

Yes it was only over a few weeks... there is a noticeable amount on the bottom..I can feel them when i run my hands under my hull at the dock.

I think my skin would stick to the riser if i held it there for a minute....

Also I have to get a closer look but right before i was about to leave the boat the other day it was running and on the port side of the engine i noticed a line/hose smaller in diameter and it was twitching...sounded and looked like what ever was flowing through was having trouble... like i said i have to get a closer look at that to find out what it is

 

[jy118lfd]

Re: lacking power all of a sudden...here are the syptoms

Yes it was only over a few weeks... there is a noticeable amount on the bottom..I can feel them when i run my hands under my hull at the dock.

I think my skin would stick to the riser if i held it there for a minute....

Also I have to get a closer look but right before i was about to leave the boat the other day it was running and on the port side of the engine i noticed a line/hose smaller in diameter and it was twitching...sounded and looked like what ever was flowing through was having trouble... like i said i have to get a closer look at that to find out what it is

If the risers are that hot then you might have melted an exhaust shutter and it made its way down the pipe and is blocking the exhaust flow. Hence the sound like the motor is laboring. Thats the first place to look as the risers have to come off anyway to check for corrosion.


Also see if you can turn the distributor by hand. If it is loose it will retard the timing andmake the motor labor as well as give you a shutting off issue.

 

[sethjon]

Re: lacking power all of a sudden...here are the syptoms

Doubt its barnacles since power loss was sudde but they should be removed anyway.

 

[aktrucker]

Re: lacking power all of a sudden...here are the syptoms

Also see if you can turn the distributor by hand. If it is loose it will retard the timing andmake the motor labor as well as give you a shutting off issue.

I didn't even think about that.....I have been fighting an issue with mine that was making me pull my hair out. My distributor hold down clamp is worn out, I have been trying to find a new one. I even went as far as to try and tweek it to make it hold better.....it helped, for about 20 minutes then right back to the same issue of the dist moving. Anybody know where I can get a new one?

 

[jy118lfd]

Re: lacking power all of a sudden...here are the syptoms

I didn't even think about that.....I have been fighting an issue with mine that was making me pull my hair out. My distributor hold down clamp is worn out, I have been trying to find a new one. I even went as far as to try and tweek it to make it hold better.....it helped, for about 20 minutes then right back to the same issue of the dist moving. Anybody know where I can get a new one?

This and a can of black spray paint

http://www.jegs.com/i/Moroso/710/26200/10002/-1?CT=999

 

[Bondo]

Re: lacking power all of a sudden...here are the syptoms

This and a can of black spray paint

http://www.jegs.com/i/Moroso/710/26200/10002/-1?CT=999

Ayuh,... No need for that,....
Just take a BFH,+ Beat alittle curve back into the 1 he's got,...
Works just like Brand New...

 

[aktrucker]

Re: lacking power all of a sudden...here are the syptoms

Ayuh,... No need for that,....
Just take a BFH,+ Beat alittle curve back into the 1 he's got,...
Works just like Brand New...

Already did that......won't hold the curve I put in it