15x13 prop for 22' boat????

[sebas54]

I have a 22' 1980 aquasport with a 4.3l merc. alpha. I am running a 15x15 prop and max rpms are 4300. I put on a 15x18 and was running at 3900 rpms. So, if my math is right I need a 15x13 prop.

Do 22' boats usally take a prop pitch that small?

Does this seems right?

Thanks

 

[steelespike]

Re: 15x13 prop for 22' boat????

Please read the stickies at the top of the page.Details on the boat?
We need the max rpm and speed with each prop.How is the hole shot?
Something isn't right get us those specs and we can probably figure out whats up.

 

[sebas54]

Re: 15x13 prop for 22' boat????

15x15 wot 4300 rpms going 26mph
15x18 wot 3900 rpms going 28mph

I think rated max rpms for my engine is 4600-4800 rpms.

Hole shot seems good for both.

How fast is my boat supposed to go?

 

[steelespike]

Re: 15x13 prop for 22' boat????

Unless that boat is a real load I'm guessing around 40 would be normal with a light load.My guess is a 19" pitch would be close to normal perhaps even a 21 if you weren't interested in a good hole shot.
Is the bottom clean?(there is a post here where bad paint reduced rpm something like 1400)Throttle opening all the way,how is the compression,
is it running on all cylinders?

 

[sebas54]

Re: 15x13 prop for 22' boat????

I did the compression test a couple of months ago, all were the same 145 except one and that one was only about 10 psi off. The bottom paint is good just did it. the prop is new. I think I am running on all cylinders. The boat is heavy, 1980. Full tank.

How can I tell if the throttle is opening all the way.

Should I get a 21" pitch prop? Wont this bring my rpms down?

So, a 13" prop is no good on a 22' boat?
thanks

 

[MikDee]

Re: 15x13 prop for 22' boat????

Wait, 22' That's a heavy boat for a 4.3V6, is it a 2bbl carb, or 4bbl? but somethings wrong, I think top speed should be at least maybe 35mph. A 21" pitch prop is too much! But I think you should be able to run a 17" prop, if your engne were strong. I personally think you have engine issues. Check your throttle opening, with the engine off, put it in gear, and at full throttle, then go back, & look down the carburetor barrels (you may have to hold the upper butterfly's open with a screwdriver), the lower butterfly's should be wide open.

Next, check the spark advance take off your distributor cap, and grab the rotor, then gently make sure it can move some in a clockwise direction, and spring back on it's own, if not the weights in the bottom of the distributor are frozen.

Once you check all this get back to us, before you even think about re-propping.

 

[sebas54]

Re: 15x13 prop for 22' boat????

It has a 2 barrel carb. I will check the dist. and throttle opening. Thanks

 

[steelespike]

Re: 15x13 prop for 22' boat????

I did a little checking At 2200 I wouldn't call a 22 footer a load.
170 hp probably adequate I saw Grady 21 that was 2850 and another that was 3,000. Both with 140 hp There must have been an upgrade.
I did notice a Aquasport that was called a Deep V might account for a slightly slower speed.

 

[hwsiii]

Re: 15x13 prop for 22' boat????

Sebas, I have a couple of forms, if you are willing to take the time to fill them out I will be glad to try and help you figure out what is going on and what is the correct prop for your boat.

H

 

[MikDee]

Re: 15x13 prop for 22' boat????

I did a little checking At 2200 I wouldn't call a 22 footer a load.
170 hp probably adequate I saw Grady 21 that was 2850 and another that was 3,000. Both with 140 hp There must have been an upgrade.
I did notice a Aquasport that was called a Deep V might account for a slightly slower speed.

steelspike, 2200 what? lbs? Is that the hull alone? Or the whole package? That V6 Mercruiser package alone must be over 1000lbs! That would leave the 22' hull to be 1200lbs!, meaning it's lighter then my 89' Bayliner Skiboat (Cobra style) hull, which is 1500lbs alone I don't think so

 

[steelespike]

Re: 15x13 prop for 22' boat????

Perhaps the NADA listing is wrong It says stern dr. 2200 lbs 170 hp.
the 19ft stern dr.is listed at 1750.
It does list your boat at 150hp 2,000. That would seem to indicate your hull
less motor is about 1630.
Seems the Aquasport listing is messed up.

 

[sebas54]

Re: 15x13 prop for 22' boat????

I just checked the throttle and rotor. The throttle opens up completely. I removed the dist. cap and turned the rotor as much as it could clockwise, about a half an inch, It didn't go back to the original position. It stayed at the point where i turned it.

Is this my problem? What is the purpose of the rotor coming back? I changed the rotor and cap at the beginning of the season.

How can this be my problem if the boat runs and start up.


Thank you.

 

[MikDee]

Re: 15x13 prop for 22' boat????

A corroded spring, & weight, advance mechanism below the breaker plate. It should move freely, & bounce back easily.

 

[sebas54]

Re: 15x13 prop for 22' boat????

I was told that there are no weights in a thunderbolt IV.

 

[wca_tim]

Re: 15x13 prop for 22' boat????

I was told that there are no weights in a thunderbolt IV.

not in mine anyhow...

my balsa cored 17 ft checkmate was on the order of 2300 pounds with a 4.3 in it... and a hundred pounds more with the v-8. that's a fairly light and small boat... I'm surprised at the low weight... anyhow.

 

[MikDee]

Re: 15x13 prop for 22' boat????

I was told that there are no weights in a thunderbolt IV.

I didn't think they had a thunderbolt IV in 1980?
Then it may not have weights.

This is my 19' Ski boat, it weighs 1450:
http://www.nadaguides.com/default.a...&m=0162&y=1989&ml=B&gc=MR&gtc=MR&d=1600018576