merc 260 wont get WOT!HELP

[paragod]

I have a Merc 260 that runs great brand new rebuild it had an older MR that blew up I put a new 1984 drive from a 228 merc I think it is an alpha 1 any way took the boat out and it wont make more than 3800 rpms carb is wide open and its running great but need more rpms shes drinking the fuel and working to stay on plain it has a 15 3/4 17 p alum prop From the prop guide for this drive and engine it looks like the dia of the prop is to big any suggestions would the smaller dia fix this its a 23ft 233 LS Formula

 

[dick]

Re: merc 260 wont get WOT!HELP

Can you confirm the ratio of the new drive ? If the newer drive came from a v-8 and your using the same prop you should be getting the WOT.

 

[Walt T]

Re: merc 260 wont get WOT!HELP

Prop diameter wont fix it. Check your gear ratio. With that prop you should be way under propped. and overreving. If the ratio is okay you have something seizing such as a gimbal.

 

[paragod]

Re: merc 260 wont get WOT!HELP

the gimbal was brand new when I put the drive on and it all went together like silk. The Alpha came off of a 19 ft Sea Ray with a 228 V-8 chevy Mercruiser. If I take the top cap off of the drive this is were I can count the teeth correct?

 

[dick]

Re: merc 260 wont get WOT!HELP

Anyway, yes is you count the teeth in the upper you can figure out the ratio.

 

[paragod]

Re: merc 260 wont get WOT!HELP

Ok there were 22 teeth on the input drive gear this would be a 1.5;1 correct? any more ideas thanks ! guys

 

[MrBill]

Re: merc 260 wont get WOT!HELP

Gear ratio is the issue. The Mercruiser 260 (1978-1982, serial range 4898730 THRU 6225576) was mated with a higher gear ratio drive. The original set up probably worked well with a 19P prop, but obviously that will not help your current set up. This type issue has been debated in this forum many times, but when the outdrive ratio is too low, there is little that can be done, its got to be changed. This impacts the lower unit gears.

 

[paragod]

Re: merc 260 wont get WOT!HELP

so do I need the 1;65 or 1;35 1;35 correct and then I could get in to higher pitch props to manage the rpm s? thanks for your help

 

[Bondo]

Re: merc 260 wont get WOT!HELP

The 1.65/1 is the Lower gear ratio......<br />1.32/1 is a Higher ratio...<br />The 1.32s are somewhat Rare, they were used on the Big Block motors for a couple of years.....<br />The Standard Ratio for a V8 running at sea level is the 1.50/1.... This IS the ratio you're Supposed to have... A Good Running 350 Should be Spinning at over 5000rpms, with your outdrive,+ a 17" prop......<br /><br />I'd keep looking for a Problem........<br />Either your engine Isn't putting out the HP it Should be, Or you've got Something Binding, Or your boat set-up is Wrong Somewhere, Or your boat bottom is covered with growth, Or ?????<br /><br />As Asked Before, What was your WOT with the Mod.1 that you blew up ?????????<br /><br />I don't know What your Problem is, But I'd start by Testing/Tuning the Engine again.... An Air restriction Maybe ?? Then move onto the Drive.... <br />A Smooth running motor doesn't mean it's making Full Power......<br />A 23' boat with a 350, Should be spinning a 19" or larger prop to Full WOT........

 

[Walt T]

Re: merc 260 wont get WOT!HELP

With the 17 prop you should be running a 1:65 ratio.

 

[paragod]

Re: merc 260 wont get WOT!HELP

I dont know what the MR drive did it was in a basket with all the gears broke due to bad alignment.I can turn everthing nice and easy by hand I talked to a Master tech at the Local Formula dealer and they said this set up has no bussiness with a 15 3/4 dia prop drop down to the 14 inch diam and it should fix the problem. Thanks I will keep u up to date keep looking!