Top speed question:1973 18 ft Searay 302 mercruiser 888

[searaychad]

Does anyone what kind of top end I should be hitting? I had a searay with same year but was a 19 ft with the same engine that would top out at 48 mph (fully trimmed out).The searay I have now is 1 ft shorter,lighter and does about 44 mph.And it has a stainless prop.The 19 ft didnt and was still faster.Both had 19 pitch props.Any ideas?

 

[Fordiesel69]

You forgot to mention RPM. If your engine is not reaching 4400 ~ 4800 it is not running correctly or somthing is up with the prop. Have you checked your hull weight? Could it be water logged?

 

[searaychad]

I'm hitting about 4200 rpm with the out drive trimmed.It does have a really good hole shot,and the boat doesn't feel heavy.My Clymer's manuel says redline is 3800 to 4200,which seems low to me.I'm getting a little older now so I no longer need to go mach 1 on the river,but 50 on on a 18 ft boat with a V-8 seems reasonable.

 

[Fordiesel69]

You should be running just a tad more rpm. Look at the timing advance inside your distributor. Also count the teeth on the upper unit and make sure the drive is the correct one for the engine. I just went thru this on my glastron. I had a 1.98:1 on there with a 19p prop and it went 44MPH at 5200RPM. My new drive 1.65:1 goes 40MPH at 4400PRM. You can turn that 302 4400 ~ 4600 no problem, just don;t hold it there too long (as with any old engine). Feeling heavy and being heavy is diffent. You can weigh the boat on the trailer, then just the trailer and subtract. This will tell you for certain.