5.0L OMC RPM and prop?

[Purduebarry]

Well I've done as asked and clicked through the universe first to no avail, so here goes...I have a 1988 Bayliner with a 5.0L and Cobra Stern drive. I'm trying to find out the factory recommended RPM range at WOT. I think it's a Chevy, distributor is aft. I have a Michigan Wheel prop 14.5 x 19, I think it is the OEM prop or at least the only prop the boat has ever seen. The Michigan Wheel website suggests this is for 36-44 MPH, which seems right because anything beyond that speed I seem to lose power (cav and/or vent). I need a new prop, to get this right however I need to know the RPM. I'm going for a better performance prop such as Vortex or Rapture, nothing crazy but just better overall performance. I've read that over rev or lugging are both bad so I want the best overall combination and best tuned prop for the boat. I have other questions but I'll refrain for now to be fair. Thanks in advance for all the knwoledge out there, I spent the last three hours reading all about my new "hole in the water".

 

[TilliamWe]

Re: 5.0L OMC RPM and prop?

Purdue, welcome. Don't be surprised if this gets moved to "prop" questions.<br />If that is a Chevy engine, the factory rpm range will be in the neighborhood of 4400-4800. Most all the 350's of that era were in that range. Others will know exactly.<br />What size/type of Bayliner do you have. The condition you describe here:

The Michigan Wheel website suggests this is for 36-44 MPH, which seems right because anything beyond that speed I seem to lose power (cav and/or vent).

doesn't seem right. You shouldn't lose power or ventilate your prop on the top end, unless you are trimming it up/out too far. Is that what you are doing? Over trimming trying to get more speed.<br />What RPM's are you turning WOT with your current set up? And if you don't have it, get the July 2005 issue of Trailer Boats Magazine. Very good prop info in there.

 

[Lou C]

Re: 5.0L OMC RPM and prop?

I agree, I get about 4400 on my OMC 4.3 V-6 with same prop, you must be trimming up too far.

 

[rbezdon]

Re: 5.0L OMC RPM and prop?

Perdue, I I have a 1988 Bayliner Capri 1950 wihich came with the OMC Chevy 5.0. Per the manual the WOT is 4400 to 4800. Mine does 52MPH at 4800 with the 14 1/4 by 19 aluminum. I have since upgraded the block to the 5.7 and get more hole shot but not mush more top end. I am turning about 53 MPH at 4600 RPM turning a 14 1/2 by 21 aluminum Michigan. Great hole shot though, even with 6 people and a tube. I think I may be carrying some extra "water" weight in the foam under the floor. The floor is getting soft and the boat has bee kept out side it whole life through all seasons so I am considering pulling up the floor next year. If I get the soggy foam out of there I expect I can get over 55. I did it once about 10 years ago with the 5.0 and a 21P Stainless prop.

 

[Purduebarry]

Re: 5.0L OMC RPM and prop?

Okay I'll keep this related to motor stuff and go to the prop section for that later. I have a 1988 19.5' Bayliner Capri 1950BR with 5.0L. Just to wrap up this part of the equation I need to make sure I have a Chevy...I was told that if the Distributor is aft it's a Chevy and if fore it's a Ford, any other distingushing things? It does have a Quadrajet carb, I think it's a 4 barrel but I haven't started my tinkering yet and haven't pulled the filter to be sure. Also from what I've read I have the "DOG" Cobra stern drive. <br /><br />As for the triming questions, the runs I've made is with the trim ALL the way down. I've only recently heard to trim up a bit for more speed and haven't tried this yet.<br /><br />Is this the best place for more motor questions? I'll have some in the coming weeks for tune-up, winterization etc. Of course the boat came complete with EVERTYHING except the Owners Manual! <br /><br />I JUST bought this boat and I'm committed to making this thing work out for a few years without any major problems, so I can convince the wife this was a smart decision. If you guys keep helping me out, I'll be a lot better off in the long run!

 

[rbezdon]

Re: 5.0L OMC RPM and prop?

you have a small block Chevy, 100% no doubt. I have exactly the same boat

 

[Purduebarry]

Re: 5.0L OMC RPM and prop?

Vatter41. Seems like we have the same boat. I have a 1988 Bayliner Capri 1950 BR with the orig. 5.0L and OMC Cobra drive. Why did you upgrade to the 5.7? Also, you mentioned the elusive owners manual how can I get a copy? I'm at such a disadvantage, I don't know which version I have of anything, I'm going to spend a whole day just looking for numbers and matching parts for a motor and drive from a company that's out of business. I'm looking at some new prop options too, I'd like your opinion can you be reached via e-mail?

 

[rbezdon]

Re: 5.0L OMC RPM and prop?

No problem Perdue, my email address is vatter41 at aol dot com. I had an owners manual until I moved. Now I have a Clymers which I dont much care for. I upgraded to the 5.7 as I had a few issues with the old 5.0 which I did not want to ebuild because I froze it really bad back when the boat was new. I welded the cracks and ran it for about 12 years but when it came time to rebuild it was so easy to just get the 350 block instead of the 305. Everything is identical except the insides which you get with a long block anyway. It really didnt cost anything for my. The rebuilder wouldnt take the welded block for a core anyway so I just got the 350 and paid the core charge. I got a long block as I would have had to rebuild the heads from the old one anyway. It was a good upgrade, I do not get a lot more top end but a lot more out of the hole. Send me an email anytime!!