Slow to plane

[keelhauled]

WOW! What a great forum!<br /><br />Help!<br /><br />My boat is very slow to plane off. Here are the specs:<br /><br />1978 18' V-hull Bowrider - 185hp OMC Stringer 800 (mech shift) - 17 pitch prop (15 inch)<br /><br />The motor has very good compression and low hours. Runs great and burns no oil.<br /><br />With 2 people and minimal equipment on board, it planes nicely and runs about 38MPH at 4100RPM<br /><br />Add 2 more people and a small cooler (weight evenly distributed front and back), and it takes everything that old Chevy has got to get out of the water and not in any kind of a hurry. Takes FOREVER. Bow comes WAY up. Once on plane, it rides beautifully and very level as long as I don't back out of the throttle.<br /><br />I've tried playing with the trim (now that's a bizarre design) but that only seems to have an effect after the boat has planed off. I tried putting a couple people in the bow seats, but that did little more than scare the daylights out of them when the bow came up. Thought for a moment they were gonna be sitting on the windshield!<br /><br />The only thing that I can think of that is truly wrong is there is a little scummy buildup on the underside. Could this produce this much drag? <br /><br />Any suggestions would be much appreciated.

 

[Capt. T]

Re: Slow to plane

Do you know what the max RPM range is for your engine. I don't know about that particular setup but 4100 rpm seems on the low side. Also what rpms are you pulling when fully loaded?<br /><br />A 17" pitch prop doesn't seem excessive but your performance indicates otherwise. <br /><br />I would look at going to a 15" pitch stainless steel prop. Do you have a prop shop or dealer who will work with you on a trial basis? Good shops will let you try a prop (maybe with a deposit) or two because trial and error is really the only process that works.

 

[Jdeagro]

Re: Slow to plane

keelhauled:<br /><br />To get good information you need to provide some additional hard data.<br /><br />Here are a few questions that I would ask inorder to give you some suggestions.<br /><br />1) how long have you owned the boat. <br />2) has it performed any differently in the past<br />3) what is the engine RPMs at full throttle?<br />4) Has there been any work doone on the engine recently ( even as little as a tune up)<br />5) Is this the origional prop recomendation for this boat.<br /><br />If you doo a search on this site under three main topics you will get more information than you can deal with as your problem is not unique:<br /><br />Prop choice<br />Hydrofoils<br />Smart Tabs ( Trim Tabs )<br /><br />If you would like to contact us for specific information and Advice , call 800-233-0194

 

[Doug Durako]

Re: Slow to plane

If you have the trim design that raises the front of the motor (screw on the motor mount) you need to get it all the way UP----moves your prop IN to the back of the boat. Do you have the Chevy straight six motor---max is about 4200 rpm if that's the case so you are real close.<br /><br />Bottom scum will slow your top end-----that may be knocking off a couple hundred rpm----but should not impact your time to plane.

 

[crazy charlie]

Re: Slow to plane

Try all the easy stuff first.Take a broom and scrub bottom,make sure drive is all the way down,add a 25$ doel fin or stingray,Travel with a little less fuel and put coolers and gear and at least 1 person in the front,if not in the front then make sure no one is all the way in the back.If you have trim tabs make sure they are not pulled up.charlie

 

[keelhauled]

Re: Slow to plane

Thanks for the info. I actually just purchased this boat about a month ago and it has acted this way since I got it. It's a 305 2bbl V8 running 4100 revs at WOT so it seems to be running correctly. It's had a full tune-up (and I do mean full).<br /><br />But I guess all of this is beside the point since I found a solution to the problem. I wanted to post it here in case any one else needs the info.<br /><br />Here's the scoop:<br />The bolts securing the rear engine mounts to the stringers had worked themselves (or had help from the previous owner) loose to the point that the engine was able to rise up in the rear under load. My first thought was soft stringers, but I checked and double checked them and they are solid bow to stern. I was able to retighten them and really helped eliminate the planing problem. I doubt they will stay tight, so I'm still working on that one.<br /><br />On an unrelated note, is marine exhaust hose much different than silicone hose that I can get much more readily at the local Detroit Diesel shop?<br /><br />Thanks for the advice!