Right prop for 4.3L with 5.0 Cobra outdrive?

[Darkhorse1201]

I have a 1992 4.3L V6 that has a 5.0L outdrive on it. (I know this cuz I checked the numbers). Since the ratio is different on the 5.0L outdrive than the 4.3L outdrive, should I go up in pitch or down in pitch? The stock prop for a 4.3L was I beleive a 14.25" x 19 or a 21. Any suggestions from the people with way more knowledge than I? Thanks in advance.

 

[skiriver]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

Based on what you describe my first reaction is select a lower number pitch as the 5.0 outdrive was figured to be powered by a larger HP/torque V-8 engine. The ratio could be a .67 vs. .57 for a V-6 outdrive. Much is determined by boat type, size, potential hull speed, etc. Are you running a high performance (200+HP) V-6 in your boat? This makes a difference. It also makes more sense for a high output V-6 to have been coupled to the 5.0 outdrive.<br /> 4.3L V6 OMCs can use from a 15.5X13 up to a 14.5X24. The 5.0L OMCs can use from a 15.5X13 up to a 14.5X26. If you are in the 16' to 20' runabout range you could consider a 15X16, 15X17, 14.5X19, 14.25X21, or 14.25X23. The one that lets your boat (lightly loaded, trimmed correctly, running on glass, etc.) run your engine RPMs to your maximum throttle setting (WOT) is probably the one for you. If you just cruise the 19, 21, or 23 may be it. If you tow skiers the 16, 17, or 19 may be the way to go. Hope this helps.

 

[Bondo]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

I Don't Do OMCs,... So I can't say for Sure in your case,.......<br />But,......<br />With the Mercruisers,.....<br />Each step in the outdrive Ratio change,.....<br />Is Very Close to 6"s of Prop Pitch Difference...........<br /><br />You'll be needing a Lower Pitch,........

 

[Darkhorse1201]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

Sorry, I should have put in more info - this motor is on a 1992 18' Sunbird. The motor is 175 HP. Does a bigger dia. prop make any differance in performance? I mostly cruise and pull tubes on a small lake.

 

[Haut Medoc]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

swsidlo, if you put your query in the props forum, you will get more feed back... ....JK

 

[vipzach]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

What RPM's are you getting now, did you just get this boat? Why do you think you need a different prop?

 

[Darkhorse1201]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

Well in hindsight I probably should have put it in the porps forum but I thought that it was more of an out drive question and I was told before that it was a no-no to post the same question in 2 forums. 2nd - I dont know what kind of RPM's I get cuz I just bought the boat and it did not come with a prop. I just want to get close to what should be optimal prop for the boat because of the different outdrive.

 

[vipzach]

Re: Right prop for 4.3L with 5.0 Cobra outdrive?

I would find you a local prop shop and see if they have a "try before you buy" kinda thing. That way you can tryout a couple of different props and find out what would work for you. Your motor and drive setup could be fine. If you think the gear ratio is to low for the motor, then start out with a 17 or 19p!