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

indy440

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I have a 1993 Larson 170 bowrider. Its 17 feet long and has the 140hp 3.0l engine with electronic ignition. It has about 85 hours on it total. Im the second owner and it has been maintained very well and stored inside or very well covered outside or covered in a slip for one season.

I've had it for almost a year now, and its always run exactly the same. It starts right up, idles perfect, revs out nicely, etc, etc... I was actually quite impressed with how quickly it came up onto plane. Seems to run exactly like any boat should.

My concern is this: It only goes 36.5mph on the GPS. I've never seen a 17-19 foot bowrider equipped with the 3.0 go less than 42mph GPS. Many 17s run 43+. So somewhere Im being jipped of like 5mph, which might not sound like a lot but its significant when you're only going 30-something!

I try to keep trimming the boat up until the drive starts to hum (prop coming out of the water maybe?), and running it on several different water conditions with light loads, etc! It never goes any faster than 36.5mph.

It revs to 4800 RPMs top with a light load, and 4600 rpms with a typical load, MAX is 4600 according to the sticker on the spark arrestor.

A few things to note:

It has bottom paint. This fall's project is to remove it. The crooks at the marina convinced the old man previous owner he NEEDED antifouling paint. I hate it and will be removing it.

The temp gauge never goes over 120 degrees even if I run it wide open for 10 minutes.

The prop doesn't have a single ding or dent. But it does have some light surface corrosion.

It idles a little rough for the first minute or two after starting it cold. Some times I give it a little throttle so it smooths out a little.

I do not think its holding water under the floor. There are no signs of water or rot anywhere in the boat. Even when heavily loaded it still floats pretty high in the water.
 

nola mike

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

I have a 1993 Larson 170 bowrider. Its 17 feet long and has the 140hp 3.0l engine with electronic ignition. It has about 85 hours on it total. Im the second owner and it has been maintained very well and stored inside or very well covered outside or covered in a slip for one season.

I've had it for almost a year now, and its always run exactly the same. It starts right up, idles perfect, revs out nicely, etc, etc... I was actually quite impressed with how quickly it came up onto plane. Seems to run exactly like any boat should.

My concern is this: It only goes 36.5mph on the GPS. I've never seen a 17-19 foot bowrider equipped with the 3.0 go less than 42mph GPS. Many 17s run 43+. So somewhere Im being jipped of like 5mph, which might not sound like a lot but its significant when you're only going 30-something!

I try to keep trimming the boat up until the drive starts to hum (prop coming out of the water maybe?), and running it on several different water conditions with light loads, etc! It never goes any faster than 36.5mph.

It revs to 4800 RPMs top with a light load, and 4600 rpms with a typical load.

A few things to note:

It has bottom paint. This fall's project is to remove it. The crooks at the marina convinced the old man previous owner he NEEDED antifouling paint. I hate it and will be removing it.

The temp gauge never goes over 120 degrees even if I run it wide open for 10 minutes.

The prop doesn't have a single ding or dent. But it does have some light surface corrosion.

It idles a little rough for the first minute or two after starting it cold. Some times I give it a little throttle so it smooths out a little.

I do not think its holding water under the floor. There are no signs of water or rot anywhere in the boat. Even when heavily loaded it still floats pretty high in the water.

doesn't seem that slow for that engine. you might try a higher pitch prop for more top end given those rpms.
 

John_S

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

You need to find someone with your hull/engine combo to compare to. If you are comparing to newer 17'ers, their hulls are probably lighter, wider, and have less deadrise than yours.

Something is probably wrong with those temps, be it gauge or stuck open thermostat. It is not causing a 5mph loss though.
 

indy440

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

other things i forgot before:

Im not sure how hard the rear motor mounts are supposed to be but I can see the motor moving if I have the cover off when I first start it from cold. It shakes (rotates) side to side in its mounts for a minute or two.

The little anode fin on the outdrive its adjusted almost all the way to one side so the boat doesnt pull. When I got the boat it was near the middle and when you hit the throttle it would almost pull the wheel right out of my hands.

If you're going slow (not planning) with the wheel turned to one direction then hit the throttle, it takes off like it should have comes right out of the water and turns nicely, but when you try to straighten the wheel back out it takes two hands to pull it hard enough. Not sure if this is normal or not, this is the first I/O I've ever owned and it doesnt have power steering.
 

Howard Sterndrive

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

The temp gauge never goes over 120 degrees even if I run it wide open for 10 minutes.
1. verify the gauge accuracy with an infrared

that's too cold. The valves could be having issues if that is accurate.

2. verify the tachometer with a hand held- what pitch prop you have?

3. compression test the engine- had a 17 footer with a 3.0 only went 39 mph but 1 cyl was low at 105psi

4. tune it up and check the timing

5. clean the flame arrester

and all the other stuff from Don's list

http://forums.iboats.com/showthread.php?t=295070

I realize, you are reaching WOT rpm, but if you get the proper propeller on there, you'll probably find you really are not.
 

indy440

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

Will do a compression test and check the prop pitch tonight as long as its not raining. I dont have an infrared thermometer but might be able to borrow one...
 

indy440

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

My prop is a 14 1/2 X 17 pitch.

I didnt have time to check anything else (wish I had at least looked for the drive ratio though)
 

Howard Sterndrive

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

that's kinda low pitch for a 17 footer. I think someone may have removed a 19P and put the 17P to compensate for a lack of power.
If you put a 19P on it, your engine would probably lack the power to bring itself to the 4200-4600 rpm range.
That's where Don S.'s list comes in:
http://forums.iboats.com/showthread.php?t=295070
 

Philster

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

Don't bother with props now. That is the last thing on the list. The engine has the power to spin up to max operating RPM, so the prop isn't the issue (yet).

Nor is gear ratio an issue.

You are in "IF" territory.

IF the engine has more potential power/energy not being exploited because of tuning or other issues, THEN once you get that power applied to the prop via the current setup, you SHOULD find that you can easily exceed the max operating RPM range and THEN you'd be shopping for a new prop that SHOULD add those 3-5 MPH you are missing.

IF the engine is really up to snuff now in its current setup AND there were some dead water weight or other drag on the setup, THEN you'd not hit max operating rpm range.

But you do hit that max rpm range. So, it's possible a bigger prop was swapped out for a smaller one as the engine lost oomph over the years OR everything is fine and that's all she has to offer.

IF you are correct, and this boat has more top speed to offer THEN you should be able to discover something that is robbing POWER. You get the missing power back and add a bigger prop. Ensure the engine has the power to offer via compression check. Further, electronic fuel injection makes max HP at ideal operating temps. It might run with a less-than-desirable fuel/air ratio when not warmed up right. Personally, I would be ALL OVER that issue FIRST.


.
 

indy440

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

This weekend I'll have time to work on the boat (wife and kids will be out of town), so I plan to give it some attention. First is checking the operating temp and replacing the thermostat if the gauge is correct. Then a compression test once its up to a proper operating temp. Then check the timing. Then I'll come back here with the results.
 

Howard Sterndrive

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

The engine has the power to spin up to max operating RPM, so the prop isn't the issue

not an accurate synopsis

If you put an 11P prop on a boat, you can get to WOT with 1 spark plug wire removed

you can't test for power without putting a proper load on the engine

a 17 foot runabout with 1.98 gears and a 3.0 is well known territory...
they almost always have 19P props
with lighter loads can run a 21P AL or 19P stainless


The OP might want to look at the front of the engine crank to verify his engine is a 3.0, and not a 2.5

3.0 has a harmonic balancer or dampener on the front of the crank
2.5 has only a pulley
not sure Merc was using the 2.5 past 1989 or so though...
 

indy440

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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.
 

Philster

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

not an accurate synopsis

If you put an 11P prop on a boat, you can get to WOT with 1 spark plug wire removed

you can't test for power without putting a proper load on the engine

a 17 foot runabout with 1.98 gears and a 3.0 is well known territory...
they almost always have 19P props
with lighter loads can run a 21P AL or 19P stainless


The OP might want to look at the front of the engine crank to verify his engine is a 3.0, and not a 2.5

3.0 has a harmonic balancer or dampener on the front of the crank
2.5 has only a pulley
not sure Merc was using the 2.5 past 1989 or so though...

What you did by cutting off my quote is unethical and in poor taste. I said, "Yet". You decided to remove that. The whole body of my posting must be read to appreciate the out-of-context quote you just grabbed.

I addressed the prop issue and did not tell him it wasn't the prop. My procedure is spot on and I even went on to say a larger prop could have been replaced by a smaller prop when the engine lost oomph over the years.

To correct you: You can run any prop that fits and reach WOT. WOT is wide open throttle and a prop will not stop you from running WOT. Being over-propped would keep you from reaching the maximum RPM operating range. If you lose power in an engine, it will still run at WOT. If you add a bigger prop than the engine can handle, it will still run at WOT.
 

Big Boat Bay Buster

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

Do you have a Doel-Fin or whale tail on it?
I had an 18 foot boat without power steering that was hard to steer in the manner that you described. After removeing that stupid fin from the outdrive I picked up a few MPH and it was a bit easier to steer.
Was the previous owner into water skiing and tubing?I bet the P/O wanted a better hole shot and put on a 17 pitch. You want a better top speed.
Keep this simple--buy or borrow a 19 pitch prop--They are the most popular and good used ones can be found for next to nothing. I bought a 19P at a local boat yard for $30.
Chris
 

indy440

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

no whale tale...

The previous owner was an old man that used it to cruise a freshwater river and do some fishing.
 

John_S

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

not an accurate synopsis
If you put an 11P prop on a boat, you can get to WOT with 1 spark plug wire removed

you can't test for power without putting a proper load on the engine

a 17 foot runabout with 1.98 gears and a 3.0 is well known territory...
they almost always have 19P props
with lighter loads can run a 21P AL or 19P stainless

I would agree with Philster, that the prop is not where to be looking now, unless he can easily exceed the recommended wot rpms. In your example you created a engine problem, not a prop problem. At this point, throwing another prop at this is $ wasted.
 

Philster

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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. :)
 

indy440

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

-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.



This is the plan for this weekend.
 

Howard Sterndrive

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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.:rolleyes:

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
 

indy440

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

I was also thinking about popping my drive off to check the engine alignment and make sure that my gimble bearing feels good since I'll actually have time to work on the thing.
 
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