1995 Larson 174 33 mph?

[mpursley1900]

I just bought this boat and it has a 4.3 with a 19 in prop. Couldnt get it over 33 mph and 3300 rpm at WOT trimmed to a little over 1/2. Replaced carb with a new one and it runs better but still same top end. RPM range is 4200-4600. A 19 should be about right. Timing is correct and boat idles smooth. Either a dead cylinder or lack of fuel? What speed should I expect from this boat?

 

[bnicov]

Re: 1995 Larson 174 33 mph?

Couple of questions, firstly: Verify that your tach is correct with a shop tach on a full throttle run, secondly: Verify that your speedometer is correct with a GPS.

 

[Don S]

Re: 1995 Larson 174 33 mph?

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.

 

[mpursley1900]

Re: 1995 Larson 174 33 mph?

Couple of questions, firstly: Verify that your tach is correct with a shop tach on a full throttle run, secondly: Verify that your speedometer is correct with a GPS.

Tach is correct and gps verified speed. Cant trim more tha 5/8 up. prop has a small dent at the base of one of the blades...maybe this is keeping it from hooking up?

 

[Don S]

Re: 1995 Larson 174 33 mph?

Perhaps if you could let us in on what engine and drive you have. Type of boat means nothing. Engines full model number or serial number would be nice.

 

[mpursley1900]

Re: 1995 Larson 174 33 mph?

Perhaps if you could let us in on what engine and drive you have. Type of boat means nothing. Engines full model number or serial number would be nice.

4.3 volvo penta sx drive

 

[Don S]

Re: 1995 Larson 174 33 mph?

I know it's a 4.3, but what model number. There are several versions of the 4.3.

 

[mpursley1900]

Re: 1995 Larson 174 33 mph?

I have no idea. Long story short no matter what model it is i am trying to find out what the top speed should be. Not starving for fuel or missing. Maybe the small prop ding or the whale tale are cusing cavitation problemd

 

[honeys money]

Re: 1995 Larson 174 33 mph?

I would think at boat should run close to 50mph, I have same boat with 3.0 and it runs a little over 45mph.

 

[mpursley1900]

Re: 1995 Larson 174 33 mph?

Problem solved. Previous person had crossed 2 plug wires. Boat runs great now!