cant get enough rpms

[GKT]

i have a 1980 black max 200 on a 20ft center console and its only getting 5000rpm and around 33 mph. i had a 19pitch prop on there before and it was around 4500rpm and 27mph. I switched it out for a 17pitch, reajusted the timing(it was off)...checked the float levels on all carbs. and im still just getting 5000rpm. the book says wot rpm is 5300-5800. i suppose i need to go down to a 15pitch? this seems a little too low of a pitch though. wont i lose mph? any help?

 

[jeffersondodson561]

Re: cant get enough rpms

compression test?

 

[GKT]

Re: cant get enough rpms

compression checks out good. all around 120

 

[Faztbullet]

Re: cant get enough rpms

Easy fix.... your motor has the wrong gear ratio. Someone has installed a 2:1 ratio off a 2.0 liter engine , you need the 1:87 ratio for the 2.4 liter. You can check this with a prop calculator. If you had the 1:87 with 17p prop @5000rpm your speed would be 38 mph,5500 rpm will get ya 42 mph.

 

[Faztbullet]

Re: cant get enough rpms

You can also turn the flywheel by hand while in gear, cout how many times flywheel turn to make 1 turn of prop...

 

[GKT]

Re: cant get enough rpms

dang. thanks man. you're good. do i just need to get a new set of gears and install them or a whole lower unit?

 

[Faztbullet]

Re: cant get enough rpms

If $$$ is no object, go to SEI website and order ya a new one for $795 plus $45 shipping...
http://www.sterndrive.cc/mm5/merchant.mvc?

 

[GKT]

Re: cant get enough rpms

oh. i just looked in my service manual and it says the gear ration for the 200hp serial number 6201969 and below is 2:1..my serial number is like 53 something. the 175hp and other 200hp motors are 1.87:1 though. or will it even matter if i convert mine to 1.87?

 

[GKT]

Re: cant get enough rpms

never mind...i see the 2:1 is for a 20 inch shaft. 1.87 is for 25inch. mine is 20 inch with a 5 inch spacer...ohhhhhh

 

[Faztbullet]

Re: cant get enough rpms

You are correct, I looked in my manual(90-97658) and it shows the 2:1 ratio for that year(80-81). Go back to the basic's and check spark as you may have a switchbox bad and running on 5 cylinders and check ratio by hand as previously posted...

 

[CharlieB]

Re: cant get enough rpms

Rig some LONG jumper wires and DVA test stator at Problem speed. And you will have to do it twice, to verify that BOTH ignition boxes are getting the same voltage/current from the stator.

If voltage is not to spec it will limit RPM and power.

 

[GKT]

Re: cant get enough rpms

i do know that the starboard bank of cylinders is hotter to the touch than the port side. but i have both thermostats in. im out of ideas. i dont see how changing the gear ratio would increase the rpms. if anything, i would think it would lower them.

 

[jeffersondodson561]

Re: cant get enough rpms

Have you done a cylinder drop test. Find fuse pullers at Home Depot/Lowes increase speed to no more than 1000 rpms on flushette and pull the spark plug off the plug and listen for rpm change. Sounds like you have a dead cylinder. Possible plug or switchbox etc.

 

[GKT]

Re: cant get enough rpms

i did notice that number 3 cylinder is carbonized. (i pulled the heads) the entire head is black with carbon. but that means its getting spark. so i checked the carburetor for that cylinder and all that stuff is fine too. ive got all new coils

 

[GKT]

Re: cant get enough rpms

the spark plug for #3 cylinder is black and carbonized too. all the spark plugs are old. i dont know how old since i just got the motor in august.

 

[GKT]

Re: cant get enough rpms

and i do notice that after every trip i have fuel dripping from a/the carburetor(s) somewhere (looks like out the front).

 

[jeffersondodson561]

Re: cant get enough rpms

You need to verfiy spark on every cylinder.