Which direction pitch?

[Chumlee]

OK Where to start?
1999 Lowe 180
20 gallons of premix
1984 90hp evinrude v4
2 big batteries
carbs rebuilt- butterflies are opening til completely flat (opening all the way)
Decarb motor with seafoam
new plugs
lower unit- new seals and bearings
2 passengers

Motor seems to be running smooth (No misses)
My prop right now is a 13/14 x 19 4 blade solex. At wide open throttle, I am running 35mph at around 4200rpm. Which direction in pitch do I need to go to get to 5000rpm to 5500rpm?
Thanks for the info.

 

[hwsiii]

Re: Which direction pitch?

Lee, running your numbers I show you need to drop to a 15" pitch in the prop you are running right now if your gear ratio is 2:1. Here are the numbers.


Prop Change

H

 

[junior1113]

Re: Which direction pitch?

i would work on setup and buy a 15 pitch. where is cavitation plate in relation to bottom of transom. can you post a pic of this. if motor can go up without cavitation rpms will go up. 5500 is what i'd shoot for if you want motor to last. hole shot must suck with those #'s. probably going to be needing a 15 pitch and raise motor to bring rpms up 700 or more. if tach is accurate you are lugging your motor if wot rpms are only 4200. in fact i would'nt even run it like that. and if you do rebuild is going to be very soon. check tach

 

[Dhadley]

Re: Which direction pitch?

I'm with Jr about the set up. I'd work that with the current prop to max it out and get a true baseline. Then look at a smaller prop if needed. If this is an aluminum boat that motor should be a lot closer to 5000 if it's running right and the tach is correct.

When you mentioned 35 mph at 4200 we'll assume that was wide open.

 

[Chumlee]

Re: Which direction pitch?

Ok here are some pictures.
How do i know gear ratio?
Maybe i need to hook up another tach to be sure.
Dont happen to know which wires on engine to hook temporary tach to?
Thanks again

 

[Chumlee]

Re: Which direction pitch?

Sorry forgot pics

 

[Chumlee]

Re: Which direction pitch?

yes that is wot and using t/t to gain the rpm and speed

 

[Dhadley]

Re: Which direction pitch?

That motor should scream on that boat even with a 19. Unfortunately someone has drilled the transom wrong. The motor is all the way down but the bolts look like they're in about the 3rd hole. It'd be nice to raise that motor and see how it responds with that prop.

A dealer will have a shop tach which just clips on a plug wire so you can test it quickly. However, I'd sure think that boat would be faster than 35 if the motor is running right regardless of what the tach reads.

I'd raise the motor even if it's just the one hole and see how the rig responds. If it responds favorably then we can look at the options.

Make sure the motor is reaching at least 26* of timing at wide open but no more than 28*.

Yes your gear ratio should be 2:1 with a 13 spline propshaft.

 

[Chumlee]

Re: Which direction pitch?

update:
Ok I raised the motor to the last hole. I gained about 3mph but my tach still showed 4200. Motor ran fine no cavitation execpt when trimmed out and taking hard turn. Trim down a little and good to go. Motor sounds pretty solid no misses. I have a couple of the little vaccuum lines behind the carbs that look like the are leaking a little because it looks like a little oil is coming out. I will pull carbs this sometime this week and get these replaced.
I am thinking something is wrong with tach so I ordered a shop tach to see what motor is really doing.
Pulled plugs and they were quite oily (I did away with the oil side of the vro, running 50:1 premix, figured this caused little when running slow). Did compression check. All cylinders were from 123 to 120. So the only thing i can figure is the tach is off. I got a shop tach coming and i will update after it come in. Thanks for the help. it is much appreciated.