Am I getting top performance?

[jhitt]

I was just wondering if I am getting the most out my engine. I have an 87 Century 4000 21' Cuddy with a 260 Mercruiser. I have tuned and tuned and tuned the motor. The only thing I know now is that the secondary on the carb are not opening soon enough.....anyways... I weighed the boat with trailer and it's 5600 lbs,,so guessing roughly 4600-4800 boat and motor. The boat WOT tops out at 33 mph,,rechecked with GPS so speedo is right.

Is that a good speed for the size of the boat.


side note, book says 4400 for WOT, but I only get 4100... also says timing is 8 degrees BTC, but had to advance it by ear in the water to get it to run..

thanks

 

[BAproject]

Re: Am I getting top performance?

no..it should be going faster, like 40+

do you have the correct prop?

and you should be up around 4400rpm at WOT

 

[jhitt]

Re: Am I getting top performance?

thanks

I would guess the lack of RPM could be from the carb secondaries and maybe a tweak with the timing. I have gone through ever thing else.

Motors I know all about,,,anything behind the crankshaft, I'm learning....

The right prop, I don't know. I will have to do some research. We did knick the heck out of the prop on it recently, so a new prop is something I am in search of. But again, I know nothing about props.

 

[Bondo]

Re: Am I getting top performance?

I have tuned and tuned and tuned the motor. also says timing is 8 degrees BTC, but had to advance it by ear in the water to get it to run..

Ayuh,... How about a Compression Test during all this Tunin',..??

Like I said in your other thread,... Set the timing back to where it Belongs,... 8?btc...

 

[sethjon]

Re: Am I getting top performance?

I was just wondering if I am getting the most out my engine. I have an 87 Century 4000 21' Cuddy with a 260 Mercruiser. I have tuned and tuned and tuned the motor. The only thing I know now is that the secondary on the carb are not opening soon enough.....anyways... I weighed the boat with trailer and it's 5600 lbs,,so guessing roughly 4600-4800 boat and motor. The boat WOT tops out at 33 mph,,rechecked with GPS so speedo is right.

Is that a good speed for the size of the boat.


side note, book says 4400 for WOT, but I only get 4100... also says timing is 8 degrees BTC, but had to advance it by ear in the water to get it to run..

thanks

You're almost topped out. I doubt if your gauges are right on. If you want a little more top end change the prop but realize you will give up a little on the hole shot. 33 is not bad. What are ya gonna do with only about 3-4 more MPH?

 

[sethjon]

Re: Am I getting top performance?

thanks

I would guess the lack of RPM could be from the carb secondaries and maybe a tweak with the timing. I have gone through ever thing else.

Motors I know all about,,,anything behind the crankshaft, I'm learning....

The right prop, I don't know. I will have to do some research. We did knick the heck out of the prop on it recently, so a new prop is something I am in search of. But again, I know nothing about props.

Get aprop that is 2 more" for a little top end.

 

[jhitt]

Re: Am I getting top performance?

with my experience, when you start checking compression you are getting close a overhaul....but I got the guage so why not.

I will got back to square one and try it all again.... thanks for the advice

 

[jtmarten]

Re: Am I getting top performance?

Get aprop that is 2 more" for a little top end.

A bigger prop will drop him into the 3800-3900 rpm range - not any better.

 

[jtmarten]

Re: Am I getting top performance?

I was just wondering if I am getting the most out my engine. I have an 87 Century 4000 21' Cuddy with a 260 Mercruiser. I have tuned and tuned and tuned the motor. The only thing I know now is that the secondary on the carb are not opening soon enough.....anyways... I weighed the boat with trailer and it's 5600 lbs,,so guessing roughly 4600-4800 boat and motor. The boat WOT tops out at 33 mph,,rechecked with GPS so speedo is right.

Is that a good speed for the size of the boat.


side note, book says 4400 for WOT, but I only get 4100... also says timing is 8 degrees BTC, but had to advance it by ear in the water to get it to run..

thanks

I always set timing to have 35-36* at full advance. If the dizzy provides 22*, I set initial at 13-14*. No sense leaving power untapped. If you go beyond 36* you take a chance of creating a nice hole in the top of a piston.

 

[jhitt]

Re: Am I getting top performance?

so are you saying I may need to keep it advanced for better performance...

thanks

 

[BAproject]

Re: Am I getting top performance?

8 btdc....

the correct prop and check compressions since you have the gauge

33mph sounds about 10mph off and you said you verified with a GPS