Mercruiser Bravo I problems!!!!!!!!!!!

[Heathery]

I have a 1995 Crownline 250cr with a 7.4. Mercruiser engine and a Bravo I outdrive.

Here is the problem:

The boat will not plane off, we get up to about 3,000 rpms and then there seems to be no more power to move her and she just revs higher. She will eventually plane off if the cosmos are aligned properly, the wind is blowing the correct direction, the current is in our favor and we wait about 5 to 10 minutes.

So far we have replaced the cone clutch, the upper gear assembly, the engine coupling and tried manufacturer suggested prop size 15 1/2 x 17 mercury mirage stainless and every other size after that, stainless & aluminum.

The engine is running nicely, she is not over heating, oil pressure is fine and everything else, she is just lacking the last push to get us moving.

Any Suggestions would be GREATLY appreciated!!!!

Sincerely,

Frustrated Boater - Heather

 

[HT32BSX115]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Have you done a compression check yet?

Also, have you had a look at the carb?


You could be experiencing fuel starvation too. plugged filters and/or plugged fuel pick-up screen in the tank.







Regards,



Rick

 

[paulrfrancisco]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Drive must be all the way trimmed down, and trim tabs all the way down for maximum affect on planing off.

I have Bravo 1 drives and I feel a similar affect and it took a lot of getting used to the "feel" of coming out of the hole. I think that the bravo 1 were race bred and they seem to not go very deep into the water...to minimize the drag I guess and It seems that they cavetate or ventelate on the hole shot...

 

[paulrfrancisco]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

The boat will not plane off, we get up to about 3,000 rpms and then there seems to be no more power to move her and she just revs higher.

So it continues to rev, but it seems to be not pushing the boat any faster? Check to make sure the trim cylinders wlll allow the drive all the way down...

 

[QC]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well 1st off, welcome to iboats Heather. I can think of some initial questions that we just need to get out of the way . . .

1) Is it a Mercruiser approved marine shop that has you replacing the clutch, coupling etc.?

2) Is this boat stored in the water or trailered?

3) What's the condition of the bottom like?

4) Do you know how to properly use your power trim? Please describe.

5) Has this boat ever run properly that you know of? Actually witnessed.

6) When you say she revs higher I assume that it gets to 3000 RPM and then seems to rev up quickly, but the boat doesn't seem to go any faster? Like things are not in gear anymore? That's why you replaced the coupler and the clutch? Your comments about "is just lacking the last push to get us moving" and "she just revs higher" seem contradictory to me. Either she revs up and doesn't go, or she doesn't rev any further. This doesn't seem clear to me . . .

7) can you describe the props you have tried more completely? Especially # of blades.

Help us get through the basics first and we can help you zero in on it . . .

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well 1st off, welcome to iboats Heather. I can think of some initial questions that we just need to get out of the way . . .

1) Is it a Mercruiser approved marine shop that has you replacing the clutch, coupling etc.?

2) Is this boat stored in the water or trailered?

3) What's the condition of the bottom like?

4) Do you know how to properly use your power trim? Please describe.

5) Has this boat ever run properly that you know of? Actually witnessed.

6) When you say she revs higher I assume that it gets to 3000 RPM and then seems to rev up quickly, but the boat doesn't seem to go any faster? Like things are not in gear anymore? That's why you replaced the coupler and the clutch? Your comments about "is just lacking the last push to get us moving" and "she just revs higher" seem contradictory to me. Either she revs up and doesn't go, or she doesn't rev any further. This doesn't seem clear to me . . .

7) can you describe the props you have tried more completely? Especially # of blades.

Help us get through the basics first and we can help you zero in on it . . .

1) The shop working on my boat is my marina and they are listed as mercruiser approved (I'm leaving the name out to avoid bad press etc)

2) The boat is water kept for traditional boating season in fresh water and stored on land for the winter

3)The bottom was sandblasted and repainted this spring and in excellent condition

4)I know how to properly trim out the boat and the mechanic has also tested, tabs down drive down and adjust from there out of the hole

5)I have not witnessed the boat run properly, I had it surveyed and took a risk on buying it which I'm starting to reget.

6)To be more clear, and sorry for any confusion in my original post, the boat picks up speed normally until we get to around 3,000 rpms where she continues to rev up into the red quickly and if you let her go she will back fire. She no longer picks up any speed after hitting around 3,000 rpms.

7)The first prop tried was a 15 1/4 X 19 3 blade stainless, unsure of the make, sencond was 15 1/4 x 19 4 blade aluminum, unsure of make as well. I know the tried the same in a configurations in a 21 pitch, again unsure of the make. The final prop tried was the manufactuer recommended 15 1/2 x 17 3 blade stainless mercury mirage.

What we were told originally is that it could be a spun prop so they changed that, didn't fixed the problem, then they said it could be the cone clutch, so they replaced that, still the same behavior, after that they rebuilt the upper unit gear assembly, still the same, then they said the coupler felt soft and said possible cause it that someone may have hit something with the drive and it blew the clutch, gears and coupling so they pulled the engine, replaces the coupling, put engine back in, sea trialed and she behaved the same. I'm at a loss. I've read a lot that says you need to make sure they are using Quick Silver High Performance Gear Lube for BravoI drives, which I was assured was the case.

I do not know if a compression check was done as of yet but I'm emailing now to verify and I will post when I hear back. They have never even mentioned that fuel starvation could be a problem.

I believe they have someone from mercruiser coming out to take a look today but I wanted to do research on my own to make sure I'm not just getting taken advatage of for being a girl

Thanks for your help and I'm happy to answer any more questions you may have!

 

[QC]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well it doesn't sound like a power issue to me. Sounds like really bad ventilation, prop grabbing air off the hull or tabs or sumpin'. Have you tried actually backing out of the throttle a little at that point? I'd try bumping up 100 RPM at a time just for fun and see what happens. It may not ventilate if the throttle is not mashed . . .

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well it doesn't sound like a power issue to me. Sounds like really bad ventilation, prop grabbing air off the hull or tabs or sumpin'. Have you tried actually backing out of the throttle a little at that point? I'd try bumping up 100 RPM at a time just for fun and see what happens. It may not ventilate if the throttle is not mashed . . .

Yes we tried the 100 RPM thing too, you can get it up on plane eventually messing with the throttle but never up over 3000 rpms with out it reving all the way up . I should have kept my little 18 footer!!!!!

I will have to pose the question about ventilation though, that would be a new angle to look at. Thank you very much for your input!!!

 

[paulrfrancisco]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Do you have an external fishfinder transducer or speedo probe located inboard of the trim tabs on the transom? If so this can cause ventalation if its installed too close to centerline or too low... If you do, try flippping this up above the planing surface of the hull. Most are hinged incase you hit something... Also look for other items like thru-hull fitings that could cause water flow distruption.

 

[tommays]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

If a 17" prop is the OEM size

I could see a performance problem that is not a lot of blade area for all the power of a BB motor trying to move that much boat


I have seen other boats with twin motors pushing 17" props have a lot of venting problem in the prop forum




Tommays

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Do you have an external fishfinder transducer or speedo probe located inboard of the trim tabs on the transom? If so this can cause ventalation if its installed too close to centerline or too low... If you do, try flippping this up above the planing surface of the hull. Most are hinged incase you hit something... Also look for other items like thru-hull fitings that could cause water flow distruption.

There is a fishfinder transducer mounted on the bottom of the transom starboard side of the outdrive, it's very small, I hope that's not the problem but I will certainly flip it up to try it, I'm open to any suggestions right now, I just want to get boating, I'm missing one of my favorite outings this weekend because of this stupid problem!!!!

As for the man. sugg. prop, we tried that and went up in pitch from there, we thought it wasn't enough prop for the boat either, she is heavy!!! She is about 6,800 pounds, most of her weight is on the port side which is annoying but common enough and easliy trimmed out when working properly. Any suggestions on diam & pitch prop? She is 26.8'

 

[tommays]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well a 3.0 LX with a 135 HP pushing a light boat makes enough power to vent a 17" prop

As far as size the question is if you nurse the boat up to top speed without venting the prop what is the WOT RPM and speed



Or can you never get it up to speed at WOT ? no matter how carefull


A B3 lower with dual props is a costly upgrade BUT is a bolt on upgrade


Tommays

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Well a 3.0 LX with a 135 HP pushing a light boat makes enough power to vent a 17" prop

As far as size the question is if you nurse the boat up to top speed without venting the prop what is the WOT RPM and speed



Or can you never get it up to speed at WOT ? no matter how carefull


A B3 lower with dual props is a costly upgrade BUT is a bolt on upgrade


Tommays

We don't get anywhere close to WOT. Once we get to 3000 rpms if we push the throttle any further, even babying her, the rpms shoot up to the redline. We thought at first she was under propped so we had them try 3 and 4 blade stainless & aluminum up to a 21 pitch.
It's getting very frustrating.

 

[Zackman]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

You may want to try posting to the Crownline forum. There are a lot of owners with the same boat that you have and may be able to give you boat specific recommendations. The Crownline Owners forum is http://www.teamcrownline.com/

Another good forum for Crownline owners is http://www.crowniehq.com/forum/

Good Luck

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

You may want to try posting to the Crownline forum. There are a lot of owners with the same boat that you have and may be able to give you boat specific recommendations. The Crownline Owners forum is http://www.teamcrownline.com/

Another good forum for Crownline owners is http://www.crowniehq.com/forum/

Good Luck

Thanks! I will certainly join and see if I can tap some Crownie Wisdom!

 

[Don S]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Have they checked the drive oil? The Bravo drive is a cone clutch drive and if not adjusted correctly, or water in the gear lube, it could cause it to slip under the higher rpm and loads.

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Have they checked the drive oil? The Bravo drive is a cone clutch drive and if not adjusted correctly, or water in the gear lube, it could cause it to slip under the higher rpm and loads.

They put new drive oil in, they said they used mercruiser regular oil, not synthetic, not sure if it was the quicksilver high performance gear lube but I have seen a lot of posts on the interent that says it is necessary to use that specific kind.

 

[Don S]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

they said they used mercruiser regular oil

That very well could be the problem. Have them put the Hi Performance gear lube in. The regular gear lube works great in the Alpha drives, but not so good with the cone clutches in the Bravo drives

 

[Reel Poor]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

One more suggestion. Look at the prop where it recesses into the lower gear case, if there is a space between the front edge of the prop hub and the gear case it will blow exhaust out of the space and cause ventelation. The prop should recess into the case a little. If it is spaced back you have a problem with the prop spacer.

 

[Heathery]

Re: Mercruiser Bravo I problems!!!!!!!!!!!

Thank you all for the suggestions, I am forwarding them on to the marina, I should know more today about what is going on and I will update this post with anything that we find.