Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Sluggish top-end on 89 sunsetter


Arctic Slalom

Recommended Posts

This spring i bought an 89 malibu sunsetter in excellent shape. The boat was in storage for 3 years prior to me buying it and the dealer sold it as a brokerage boat (they never tuned it, changed fluids, etc.)

Anyway, I brought the boat home and have driven it for about 25 hours this summer. The boat runs great, but the top-end seems a little lacking. I have the 5.7 liter mercruiser (carb), w/ borg-warner transmission, a OJ legend 13x13 prop, and the hull is in great shape (clean). With one person in the boat, running about 4100 rpms, on glass water, I'm struggling to get to 40 mph. If the boat is loaded down with 5-6 people, coolers, gear, etc. it will finally reach about 39 after about 15 seconds. Does this seem like a normal top-end speed for this malibu? I was thinking it should top out around 4400 rpms and around 45 mph.? Can thick, humid air cause a drop in speed like this? The owners manual (for the motor) says air conditons, temp./humidity can cause up to a 14% change in motor peak hp!

Are there any other 86-93 sunsetter/skier owners who have seen performace like this? Do I just need to have it tuned up/carb cleaned/carb rebuilt? When the motor manual says the WOT is from 4100-4400, does that mean i should be able to reach 4400, or will it range in that top-end depending on the conditions?

Any thoughts would be great!

thanks...

Link to comment

Check a few things like timing,carburetor, spark plugs,cap,rotor,and a fresh tank of gas. I don't think it's much more than those few things. Dontknow.gif

Link to comment

Yup, basic tune-up stuff. Can't stress enough how important a cleaned or, better yet, NEW cap and rotor are toward peak performance. Early last year I had some engine issues and Galaxy Toad recommended changing the cap and rotor, which I did. I was simply amazed at the amount of stuff inside the cap as well as the amount of corrosion on the contacts.

If this boat sat for 3 years I would highly suspect crap built up in the carb as well. A re-build is not hard to do yourself and will also likely have a huge impact on the issues of which you speak.

Edited by Baddog
Link to comment

The prop has a lot to do with it. Maybe try another prop. I wouldn't assume it's the motors problem. Maybe the hull has more of a hook on it. Some people even say if the hull is waxed it slows it down.

But a tune up wouldn't hurt. Convert your distributor points and condensor to the electronic pick-up from Pertronix. It cost me like $85. I ordered it from a performance auto store. You can look up the pertronix part number on the Pertronix site I believe. They were all the same for the 5.7 L Mercruisers.

Link to comment
  • 2 weeks later...
The prop has a lot to do with it. Maybe try another prop. I wouldn't assume it's the motors problem. Maybe the hull has more of a hook on it. Some people even say if the hull is waxed it slows it down.

But a tune up wouldn't hurt. Convert your distributor points and condensor to the electronic pick-up from Pertronix. It cost me like $85. I ordered it from a performance auto store. You can look up the pertronix part number on the Pertronix site I believe. They were all the same for the 5.7 L Mercruisers.

Is this the part you are talking about?

http://www.skidim.com/prodinfo.asp?number=PNX-ML-181

Link to comment

Thats it.

When i got my boat it was pristine. The hull bottom was just as nice looking as the top. It had major wax on the hull. It was fast. As time went on and the hull got dirtier, acid washed, dirtier, etc.. my top speed went down almost 3 mph. I admit I haven't been waxing the bottom enough and now have some water blisters and I can't get the hull as clean as it was. It sits in the water all summer.

With my current prop my top speed is ~40. Gets just over 38 while footing.

My other prop has a higher top speed.

Link to comment

I had the same boat as you with the same engine and prop. I found that it maxed out at about 41-42 @ 4400 or so. I got a new 4 blade prop and it launched harder, but maxed out around the same. Seems like the above advise of plugs, timing, etc plus cleaning the carb. I never touched the carb on mine for 14 years.

Link to comment
  • 2 weeks later...
I had the same boat as you with the same engine and prop. I found that it maxed out at about 41-42 @ 4400 or so. I got a new 4 blade prop and it launched harder, but maxed out around the same. Seems like the above advise of plugs, timing, etc plus cleaning the carb. I never touched the carb on mine for 14 years.

Do you mind reporting which 4 blade prop you purchased? I was running 46+ in my 2001 Sunsetter Lxi with FI, down to 40 right now, prop looks to have small bend. I am reading to stay away from SS due to potential damage in the event of a strike. Looking for info on 4 vs. 3 blade and size and resulting performance on this diamond hull boat! Looking for harder launch with out loss of top end and potentially "softer" wake for skiing as has been reported. Thanks!

Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...