RPM and new i/o owner questions

[knb186]

Hello I am new to this site and a proud new I/O owner. I have a 04 Glastron gx 185 with 4.3 volvo penta sx. It runs out very well but I read that it is only supposed to go to 4500 rpm. With throttle wide open and trimmed and 3 200# guys I was running about 48-50 mph and 5500 rpm's. I have a 14 1/2 23 rt prop. My oil pressure and temp never seems high and the engine does not sound like is over reving.

Am i supposed to manually limit my rpms or is it the prop that is causing this?

Also I just had the prop rebuilt ( hit a stump first time out and took out a very small section of one blade. less than 1/4") and it is now running slower than what it was before and rpm are about 100 higher. why is this? The only other thing that I had done was a new gimble bearing and boot both placed by a vovlo repair place. Last year I was running 53-58 mph.

Thanks for your time and Please help so I do not inflict more pain to my wallet.

 

[Don S]

Re: RPM and new i/o owner questions

Before you start trying to fix anything, what is either your full model number for your engine, or it's Volvo serial number.

Next, are you sure your tach is accurate? How are you getting speed? GPS or boat speedometer?

 

[Tail_Gunner]

Re: RPM and new i/o owner questions

The old man of the sea: Next, are you sure your tach is accurate? How are you getting speed? GPS or boat speedometer?....

Post your gearing it is stamped on the leg 1.66 or 1.89...Sounds like you have a blond gauge and speedo...

 

[knb186]

Re: RPM and new i/o owner questions

The old man of the sea: Next, are you sure your tach is accurate? How are you getting speed? GPS or boat speedometer?....

Post your gearing it is stamped on the leg 1.66 or 1.89...Sounds like you have a blond gauge and speedo...

it is 1.79 and i was using the speedo on boat I had my gps but i for got to reset trip so i can not look at max speed.

 

[knb186]

Re: RPM and new i/o owner questions

Before you start trying to fix anything, what is either your full model number for your engine, or it's Volvo serial number.

Next, are you sure your tach is accurate? How are you getting speed? GPS or boat speedometer?

it is sx-m prod# 3868893 and serial 4202115409

 

[Don S]

Re: RPM and new i/o owner questions

That is for the outdrive, I need the Engine numbers.

 

[knb186]

Re: RPM and new i/o owner questions

That is for the outdrive, I need the Engine numbers.

it has 2 stickers one says that the max wot for 4.3 is 4200-4600 the other that is on the side of the air intake cover says

4.3 gl-d
3869251
4012129153

Sorry about the wrong number hope this helps

Thank you for helping

 

[Don S]

Re: RPM and new i/o owner questions

I think the first thing I would check is to make sure the tachometer is correct. The 4.3GL-D is what I needed. Just wanted to verify WOT rpm for your engine, but you have the number already. I can't imagine turning 5500 rpm with that prop and gear ratio.

 

[knb186]

Re: RPM and new i/o owner questions

the only way to do that is with a hand held tach right. Can that be done with the boat out of water with the flush line or just on the trailer backed in or does it need to be in motion.

Thanks again

 

[Tail_Gunner]

Re: RPM and new i/o owner questions

Come down to the prop forums If you like. I dont believe you dont have any other issues other than a inaccurate tach and speedo. As Don said its ok... impossible to turn a 23 p prop to 5500 with combination aka with a resonalbe slip factor of say 10% that makes the boat a 60mph renegade...Cant say im 110% right but im close....Most new cell phone actually have gps try that to measure speed... 55mph would put you on the edge of being perfect.... @ 60 mph i need your guy to mend a few props for myself..

 

[Don S]

Re: RPM and new i/o owner questions

A hand held tach, or an induction tach like used in a timing light will work.
I'm going to move this thread over to the Prop forum. Like TG mentioned, it doesn't sound like you have any type of engine problem.

 

[knb186]

Re: RPM and new i/o owner questions

I am hoping to get out this weekend and I will use the gps to find my wot speed. Is it important to use the hand tach to find actual rpms or do i just run with it. sorry I am not really an engine guy and dont know much about these things.

Thanks