I think there might be something wrong with my boat, opinions wanted.

[Howard Sterndrive]

Re: I think there might be something wrong with my boat, opinions wanted.

pretty positive its a 3.0

It says 140 on the valve cover and I think it says 3.0l on the spark arrestor.

I would think so, but worth a glance... that's literally all it takes to confirm

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

Ok, just keep it simple for now. Summing up where we are at in midst of various discussion points:

-Address the temp issue.
-Ensure the engine is in good health.
-Then try a WOT run again at proper op temp and see where she winds up at top speed versus engine RPM.

I am hoping that at full operating temp, the fuel and air are metered properly for WOT and that this results in you starting to run past the max RPM operating range. With this newly-disovered power and ability to climb past the max RPM range with the current prop, you then have reason to go to a larger prop and realize the few extra MPH while knocking the RPM down to the max range.

Good luck and report back.

I agree on approach, but not nearly as optomistic on that causing any noticeable change. Being this is a carb, and colder air allows for a more dense charge, and what many performace mods strive for, vs warmer, better driveability. It is more likely that timing or a good tune-up will help improve things.

 

[Philster]

Re: I think there might be something wrong with my boat, opinions wanted.

I'm just trying to get the OP to understand how the "not reaching wot rpm" checklist might apply to him even though he is reaching wot rpm.

I didn't realize I was in unethical territory.

I think he has the wrong prop.

If he fixes the power problem and then revs to 5K, and then buys a 19P, I don't see how that makes more sense to some.
It doesn't to me.

If he's ever going to go faster, he needs a 19P
there's no getting around it if his tach is correct

the original complaint was speed, and his speed is not right. unless that boat has lead stringers

A bigger prop is not warranted until the engine produces more power.

Producing more power might come as a result of fixing a problem. Once more power is on hand, a bigger prop should be in order.

This is basic stuff here. And based on his information provided, he will spend his weekend eliminating variables and working towards the solution from the right direction.

Is there a chance he has a broken tach? Sure. I guess he could be facing a unique combo of problems all happening at once: Undepropped, with a broken tach, plus an engine mgmnt system that won't let the engine go any RPMs over the max RPM operating range. In this scenario, he spins up to max RPM, but doesn't know it, and is underpropped the whole time while the engine management system keeps him from knowing this because it won't let the engine above max RPM.

The scenario killer: That engine mgmnt system would usually make itself know by cutting power. Running at max RPM and hitting that wall would be known. Doesn't happen smoothly.

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

I think he has the wrong prop.

If he fixes the power problem and then revs to 5K, and then buys a 19P, I don't see how that makes more sense to some.
It doesn't to me.

If he's ever going to go faster, he needs a 19P
there's no getting around it if his tach is correct

the original complaint was speed, and his speed is not right. unless that boat has lead stringers

It is yet to be confirmed that he truely has a problem, let alone that it is a power problem. If it ended up being water logged foam, will the op go through all the work and expense? if the engine is just worn out, will he replace it? ...or just run it? IF either of those two items are the issue, it becomes viable option to just sell and buy another.

While most 17'ers/140 mercs can hit 40's today, back in the 80's and early 90's, not so much. Mid to high 30's was more common. Larson doesn't stick in my head as having a fast hull for the day. But, I don't know the hull or have any other info that says one way or the other.

Does someone have the deadrise and weight of this boat? So a comparison might roughly be evaluated? I did some quick searches, but couldn't find it.


My take is, get the boat in the best operating condition possible, within what the op wants to spend. If he gains enough rpms over recommended for his more common loading condition, get the more pitch prop to try. If he can hit 40, I guess that will make him happy. If he does any water toys, or ever runs heavy loads, i'd bet he will quickly miss the low end acceleration, and go back. But, I understand the need for speed.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

My goal is to make sure my engine is running to its full potential. If this means 36.5mph GPS, then I'll be OK with that.

I went and picked up a new thermostat already.

I dont have a way to verify my tach yet. I was looking at cheap aftermarket ones and they're like 40 bucks...

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

I dont have a way to verify my tach yet. I was looking at cheap aftermarket ones and they're like 40 bucks...

It sounds like you are looking at a replacement tach. Look at the shop style tach that hooks to your coil just temporarly. You really need one to set idle speed, and helps with idle mixture as well. You should be able to find one for a little less than that.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

I might have one of those! My grandfather gave me years ago and I forgot! Its really old. Maybe I still have it. Will check for that this weekend, I can't remember the last time I saw it and my workshop has been remodeled since... hmm.....

 

[Philster]

Re: I think there might be something wrong with my boat, opinions wanted.

The unlikely but possible tach headache that was introduced by someone:

The tach would have to be reading low. In other words, the idea that the tach is bad goes like this: You are at 36.5 mph because you are underpropped, with an engine that is really turning over 5000 RPM. You are above the max rpm operating range (but don't know it) and really could benefit from a bigger prop. The bigger prop will knock the RPM down a little but the return on the investment is more speed.

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

The unlikely but possible tach headache that was introduced by someone:

The tach would have to be reading low. In other words, the idea that the tach is bad goes like this: You are at 36.5 mph because you are underpropped, with an engine that is really turning over 5000 RPM. You are above the max rpm operating range (but don't know it) and really could benefit from a bigger prop. The bigger prop will knock the RPM down a little but the return on the investment is more speed.

I agree that it is unlikely his tach is off by much. But, having one to do yearly tune-ups is good. Not sure when the 4 bangers switched over to electronic ignition, but if points, needs a dwell meter, along with a timing light, too.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

is has electronic ignition so no points.

I have a timing light, and might still have a shop tach.

I also read over the procedure in the merc manual.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

What about reving the engine on the hose to check the timing? That seems risky. Should I take it to the river to check the timing?

I have amazing water pressure at my house if that makes a difference.

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

What about reving the engine on the hose to check the timing? That seems risky. Should I take it to the river to check the timing?

I have amazing water pressure at my house if that makes a difference.

Up until recently, I have never had an issue running on muffs. I haven't confirmed that the issue I am dealing with was caused by that yet, either. You should be able to rev 1500rpm easy, and some quick to 2K. That should be enough to see if advance is starting. You can recheck on the water.

Do the idle mixture and idle speed before any timing adjustment. Have the plugs, rotor, and dist cap been replaced recently?

PS: Is your local boating on Otsego Lake?

 

[Philster]

Re: I think there might be something wrong with my boat, opinions wanted.

Golden Rule is: Don't rev it over 1000 RPMs on the muffs.

Some will go with the Platinum Rule: Don't rev it on the muffs -- period.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

PS: Is your local boating on Otsego Lake?

Otsego Lake is really good if you're just going to ski and tube. Its pretty small, only about 8 miles long and 1 mile wide, and there is barely ever any boat traffic. On the weekend there tends to be a few of sailboats on the southern end, but thats about it. The only boat launch on the whole lake is TERRBILE. There is no room to turn around and its very very narrow. If you have a boat longer than 20 feet you'll be backing up for probably 150 yards from the next intersection. Its a horrible design.

We normally going to Sacandaga Reservoir. Its big (25k acres I think), with lots of stuff to do and see.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

This has been put on hold because of this:

http://forums.iboats.com/showthread.php?t=403813

 

[John_S]

Re: I think there might be something wrong with my boat, opinions wanted.

This has been put on hold because of this:

http://forums.iboats.com/showthread.php?t=403813

Sounds like a PITA kind of job.

BTW, while looking something up from another 3.0L/LX thread, discovered there is a HP diff between them. For your year L, the SM said 115HP @ prop compared to 135 for LX. This may also be a factor in your comparison.

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

So this must be 140 crank hp, and 115 prop HP...

 

[indy440]

Re: I think there might be something wrong with my boat, opinions wanted.

UPDATE

I finally fixed my starter bolt issue and got the boat fired up. I followed the timing procedure where you connect the two white wires from the distributer and connect the two wires from the interupt switch. I put the timing light on and it was flashing right at 0 degrees. Spec calls for the intial timing to be 1 degree BTDC.

I corrected the 1 degree of timing, then disconnected the white wires and reconnected the interupt switch. I was getting about 25 degrees total advance around 3500 rpms (yeah, I reved it that high out of the water. The drive is off and I had the garden hose going right into the water tube.)

Compression tested 180-185 psi on all cylinders.

So the motor appears to be healthy.