Lack of performance 3.0

Lager

Petty Officer 2nd Class
Joined
Jan 19, 2014
Messages
120
Boat new to me, 1989 bowrider 3.0 liter engine.
Standard 19 inch alum prop, max RPM I can achieve is 3000 with a light load and engine sounds like it laboring ,meaning a lot of intake honk.
Speedo inop, but Im guessing maybe 30 MPH at best.
This is less then I expected.
Since ignition timing means everything, I checked timing when I bought it. At idle is was set off the scale, Im guessing at about 16 BTDC. I reduced it to 8 per specs and the engine would barely accel with no load and had lots of intake pop back thru the carb. I set the timing back to the 16 degrees idle setting and ran it. Less then stellar performance.
Checked the point gap and dwell, all ok there, mechanical advance seems to be free.
Have not performed a compression check at this time.
Considering the age and hull design, do you think this is all Im going to get out of this pig with out changing props or is it normal?
Ive seen many newer 3.0 bowriders achieve 40 MPH easily and ride higher in the water lessening drag and a much higher engine RPM.
After all this, I dont even know what Im asking anymore?
Ignition timing ok or is this normal speed due to this age of boat hull design? It feels heavy in the water, has lots of hull drag.
Im used to high power bass boats, but the wife wanted this style of boat to bring the grandkids out skiing and tubeing.
Im not a happy camper.
 

fishrdan

Admiral
Joined
Jan 25, 2008
Messages
6,989
Re: Lack of performance 3.0

16* timing at idle is too high for points ignition, should be set to 8*. Check the ignition advance with an advance timing light and see if it's advancing properly, should be something like 28* at 2800RPM (need to check the manual for your year of engine as it will have a timing curve). How did the engine idle while set at 8*? Post up you're engine serial number and someone will direct you to a downloadable manual.

Have you done a tune-up, plugs, wires, points, condenser, cap & rotor?

How old is the fuel? If it's really old, performance is going to be bad. (drain tank and re-fill)

I wouldn't expect 40MPH out of an 89 3.0, probably more like 35MPH. What prop is on it, aluminum, SS, 3 or 4 blade, pitch and diameter?

are you running at high elevation, above 5,000'?
 

wrench 3

Commander
Joined
Aug 12, 2012
Messages
2,108
Re: Lack of performance 3.0

That timing reading bothers me. Advanced timing will help compensate for other problems, But I'm wondering if it's accurate. Idle speed could be too fast, the advance could have week springs, or the mark could be off. Find were the piston reaches the top when rotating the engine in both directions (remove #1 spark plug and stick something in the hole to feel the piston moving). Mark these positions on the crank pulley. Your 0 mark should be in the center between these marks.
 

kmarine

Chief Petty Officer
Joined
Nov 5, 2010
Messages
581
Re: Lack of performance 3.0

I like to use my cell phone gps app to check speed. works great for diagnostic work. I recommend a complete tune up and fuel filter replacement before adjusting Timing. Also check with a prop shop to see the recommended prop for your boat. My prop shop allows me to demo props before buying. You could also have a carb issue.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Lack of performance 3.0

A few issue I believe need to be looked at.

1. As already suggested, check the timing marks are correct. If the pulley is a rubber hub style, not unusual for the rubber bonding to slip..
2. Check the gear ratio in the drive. Should be 1.98:1. If the drive has been replaced in the past, it may have the wrong ratio.
3. All you have told us about the boat itself is that it's a bow-rider. What size? How heavy?


Chris....
 

Walt T

Lieutenant
Joined
Mar 16, 2002
Messages
1,369
Re: Lack of performance 3.0

Exhaust flaps? Throttle plates wide open? Choke flap open? Check free and easy basics first.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
47,306
Re: Lack of performance 3.0

Dissecting the post

Boat new to me, 1989 bowrider 3.0 liter engine.
Standard 19 inch alum prop, max RPM I can achieve is 3000 with a light load and engine sounds like it laboring ,meaning a lot of intake honk.
Speedo inop, but Im guessing maybe 30 MPH at best.


Dont guess. if you have a smart phone, download an app to get a GPS speed.
What kind of boat? hull? what is the weight of the boat, and what should it be? most boats from 1989 will have some moisture, and you could have water soaked foam, stringers, and transom which will add hundreds of pounds of weight.


Since ignition timing means everything, I checked timing when I bought it. At idle is was set off the scale, Im guessing at about 16 BTDC. I reduced it to 8 per specs and the engine would barely accel with no load and had lots of intake pop back thru the carb. I set the timing back to the 16 degrees idle setting and ran it. Less then stellar performance.
Checked the point gap and dwell, all ok there, mechanical advance seems to be free.
Have not performed a compression check at this time.

Perform a compression check. Also, intake poping thru the carb indicates retarded ignition. what is the dwell set at? if the dwell and timing are spot on, I would almost suspect the cam is off a tooth.


Considering the age and hull design, do you think this is all Im going to get out of this pig with out changing props or is it normal?
Ive seen many newer 3.0 bowriders achieve 40 MPH easily and ride higher in the water lessening drag and a much higher engine RPM.
After all this, I dont even know what Im asking anymore?
Ignition timing ok or is this normal speed due to this age of boat hull design? It feels heavy in the water, has lots of hull drag.
What kind of boat? What kind of hull. the fact that you mention newer boats riding higher in the water and yours feels heavy leads me to think your boat is currently water logged carrying about an extra 1000#.


Im used to high power bass boats, but the wife wanted this style of boat to bring the grandkids out skiing and tubeing.
High powered bass boats have a much higher power to weight ratio. Lets assume you went from a 1800# boat with a 300hp motor to a 2200# boat with a 140hp motor. now if you are water logged, add a bunch of weight and drag to the equation.



Im not a happy camper.

Lets properly diagnose what is going on, then let us help.
 

Lager

Petty Officer 2nd Class
Joined
Jan 19, 2014
Messages
120
Re: Lack of performance 3.0

Interesting thoughts and ideas from everyone and Ive got a lot of things to check on.
The boat is a 18 ft V-Master made back in 89 and its real possible it weighs more then its supposed to. The prop is made of aluminum 3 blade and in not the best of shape, some dings on it and looks original.
There is a very good chance the fuel is somewhat old, will clear that out. I know the throttle and choke are working correctly. Will check on the advance springs idea.
The engine compression check should indicate correct cam timing, thats easy enough to do.
Ignition components are new enough and there is no missfire issues so Im good there.
I will check the engine for correct TDC against the marks.
But, to tell you the truth, I think I was expecting more then what I got or bought.
When comparing this, heavy fiberglass intensive hull combined with a cast iron heavy engine supposedly producing 130Hp or so against a light weight bass boat with even a similar HP motor really isnt fair.
I agree that expecting a true 40 MPH is optimistic and I was incorrect.
Engines I understand, long time professional mechanic and high performance engine builder for many different applications.
I think what I have here is this, a heavy water logged boat with an old hull design being pushed by an old engine. I would like to see a higher engine RPM to reduce stress on the engine bearings and rods and think the only way I can achieve this is by using a smaller prop.It probably will not effect my top speed, but reduce load and thats always a good thing.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Lack of performance 3.0

.... I would like to see a higher engine RPM to reduce stress on the engine bearings and rods and think the only way I can achieve this is by using a smaller prop.It probably will not effect my top speed, but reduce load and thats always a good thing.

Spot on!
 

wrench 3

Commander
Joined
Aug 12, 2012
Messages
2,108
Re: Lack of performance 3.0

I had a 1976 Grew 17' closed deck fiberglass runabout with that same engine. It topped out at about 37 MPH. It was a little slow getting up on plane but we fixed that with a wale tail on the drive.
With that engine you should be running at least 4,400 RPM at wide open throttle. I don't know if you need to fix an engine problem, lighten the boat or get a lower pitch prop but you definitely need to get that RPM up.
 

Walt T

Lieutenant
Joined
Mar 16, 2002
Messages
1,369
Re: Lack of performance 3.0

If it's water logged that boat has outlived it's useful life. A few hundred pounds here and there wont make a difference.
 

Fastatv

Petty Officer 1st Class
Joined
Sep 28, 2013
Messages
258
Re: Lack of performance 3.0

Hi Lager, thought I would jump in here for a moment. I have a 1989 Larson DC 170, and it has the 3.0L as well. When I purchased the boat, it ran similar to what you have described about your boat. The first thing I did was remove, disassemble the Mercarb. Per the PO, carb had been rebuilt the day before I test drove it. After dis assembly, I found the main jets somewhat stopped up, and a dirty carb inside. Cleaned everything, installed on boat, picked up a few hundred RPMs. Still, at times, just about would not plane...or took forever. The next thing I did was to remove and clean every electrical connection, I mean every one of them on or around the engine, to include the battery. I used dielectric grease when reattaching the connections. Took it back out to the lake....problem resolved. Jumps up on plane...quickly, and has a top speed of 40mph. Turns 4800 ( plus ) with a 19 pitch stainless Mecruiser prop ( it actually needs another inch of pitch ). Anyway, the electrical connection cleaning did the job....which connection, well, that's an unknown, I just did them all. I hope this helps in some way. Rick
 
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smassey22180

Petty Officer 1st Class
Joined
Apr 15, 2013
Messages
210
Re: Lack of performance 3.0

I have a 3.0 and I can hit 40 with 8 smallish people in the boat. I can hit close to 50 with 2 adults and 2 kids. This is around 4800 RPM so I don't do it for long periods of time. Most of the time we are at 3k rpm and 30 mph. Most people who come here with a "new to me boat" need a carb rebuild. If you think your boat is full of water take it and get weighed. Many dumps will weigh it for free.
 
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BRG25

Chief Petty Officer
Joined
Jul 13, 2001
Messages
528
Re: Lack of performance 3.0

You're not going to be able to change the RPM that much with a different prop. If your max RPM is 3000 then something is really wrong here, whether you have a water logged hull or not. If you verify the timing is correct and the outdrive is the correct ratio I would be looking at fuel and carb.
 

Lager

Petty Officer 2nd Class
Joined
Jan 19, 2014
Messages
120
Re: Lack of performance 3.0

Just thought of something? We all are assuming my tachometer is correct.
You know whats funny? I have been an auto mechanic for more then 35 years years. I used to own dwell meters that had built in tachometers, I threw them all away 10 years ago because all I work on now are highly computerized modern engines using a $10K scanner.
A 1989 boat still uses 1960 equipment.Strangely,Im feeling lost. :confused:
Think I need to verify my tach readings first.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,306
Re: Lack of performance 3.0

any volt-ohm meter that reads frequency can be used to verify RPM
 

Lager

Petty Officer 2nd Class
Joined
Jan 19, 2014
Messages
120
Re: Lack of performance 3.0

Think I have resolution for the problem.
Tachometer in accuracy.
I just purchased a high end tach and connected to the engine and compared its readings to the original.
At 1000 rpms, both tachs read the same. But as I increase throttle , the original does not increase at the same rate as the new one.
Example, at the new tachs reading of 3000 rpm, the original only reads 1900.The ratio gets worse as the rpms go up. Ive only verified this with no load and in my drive way, But Im fully confident my engine is pulling the proper RPM of approx 4500 at full speed.
This means I feel a lot better, engine mechanics are OK, the hull is not water logged and too heavy.
With this wacky NC weather, I cant throw it into the water tomorrow to verify my readings, but Im sure this pig is giving all its going to.
I miss my nimble bass boat, but the grand kids will be happy come tubing and skiing season.
 

wrench 3

Commander
Joined
Aug 12, 2012
Messages
2,108
Re: Lack of performance 3.0

Marine tachs are like the after-market automotive tachs. They have a switch on the back for different size (number of cylinders) engines. It may be worth checking yours to see if it's on the correct setting.
 

kd7isf

Petty Officer 2nd Class
Joined
Aug 20, 2004
Messages
162
Re: Lack of performance 3.0

Its not that unusual for marine gauges to deteriorate -- remember, unless the boat is covered or has a cabin, the gauges are generally exposed to a lot more sunlight than those in a car would be...
Can also be deteriorated electrical connections between the gauge (tach) and the connection point @ the engine...

Hope this helps..
 

Starcraft5834

Lieutenant Commander
Joined
Jun 2, 2013
Messages
1,677
Re: Lack of performance 3.0

Standard 19 inch alum prop, max RPM I can achieve is 3000 rpm?--- my 2 cents... think about 16 pitch in 4 blade will push you better... 3000rpm tops? something else is very wrong here...........
 
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