RPM @ WOT Question(s)

[bds85466]

Ok so the boat I bought in '05 has an 898 outdrive and the block is an original 898 from the same year ('82).

According to the shop manual, RPM @ WOT for the 898 should be 3800-4200 (fact check?).

In 2003, the previous owner had the engine converted into a 5.7 liter 350 cid/260 nhp. It still has all the 898 badging etc, I'm guessing he just had it stroked out? (whatever that means...I'm a dummy when it comes to that stuff) Does anybody know what actually happens in that process, and what it means to me as the current owner when trying to go for different parts etc? Does it just mean that I have more power coming out of my engine (with a similar body)?

Getting back to the point: What, if any, does this do to the RPM requirement at WOT? Does it make it go up, down, or something in the middle?

Eventually this will turn into a prop question, but not quite yet!

I haven't launched her for the season yet, though I've ran it two successful seasons so far. I think I remember the RPM @ WOT to be 4500 (which is way high according to the 898 specs) with a 21" pitch prop.

 

[Don S]

Re: RPM @ WOT Question(s)

He probably just had a 350 long block installed, instead of the 305. All the accessories are the same. The 260 used the 4200 to 4600 rpm spec. If you have 4500, you are good to go.

 

[bds85466]

Re: RPM @ WOT Question(s)

I'm curious (and a bit ignorant) -- when they say the install the long block, what do they actually do? All new cylinders, valves, lifters, the works?

My plan this year is to try a 4 blade 23" pitch. If I remember right, going to 4 blades transcends your pitch downward by one. So an equivalent would be a 3 blade 22". This is a net change of only one inch to the high side -- hence meaning a drop in rpm by 100-200, correct?

Hopefully this would still keep me in the correct range (on the top speed end side?) for the stated RPM.

 

[Don S]

Re: RPM @ WOT Question(s)

Long block is block with all rotating parts, heads, timing chain and gears, pushrods, lifters, etc. No tin (oil pan & timing chain cover) or intake manifold.

Best thing you could do for a prop change is to post all your information over in the prop forum. But first, you need to take it for a run with the prop you have and get all the rpm's and speeds needed to figure out what you will need.

 

[bds85466]

Re: RPM @ WOT Question(s)

Interesting.

Wise advice, as always. Thanks Don.