Sports Car Guy
Recruit
- Joined
- Dec 21, 2020
- Messages
- 2
I know this is one of those un answerable questions, but worth asking.
I have a 1988 245 Vista OMC 260 Cobra. Main question is what speed should I expect WOT and cruise. Info I can find says the boat tops out at 39mph, which I'm guessing is optomistic, but I'm not even close, although RPM is in range. Looking for some real world speed numbers of similar boats.
First time owning a boat this heavy, had 21 ft Sylvan 140 I/O and 22 foot Trophy 260 I/O in the past. I know it's not a speed boat, its a big pointy floating camper, so I'm not expecting to pop skiers up. Had it in the water this summer, fix as I go. No real issues except vcan't get more than 10 gallons of gas in the 70 gallon tank, but that's another story
So engine runs well, runs up to 4300 rpm WOT, but I cant get over about 25 mph (GPS and speedo ) flat water with 2 people, minimal fuel and not much stuff onboard. Fresh cold water, 450 ft above sea level. (Seneca Lake NY) Needs the tabs to get out of the hole, not a surprise. If I trim drive up once it tops out and tabs are up, doesn't add much speed or RPM, starts to porpise, then prop ventilates. Trimmed out, it falls off plane if I drop below 3700. If I add 3 more people in the back, can barley get up on plane at all.
I'm using a Hustler 15x15 4 blade, worlds better than the 15.5x15 omc 3 blade which was listed as stock.
What might be wrong and what I verified. Didn't get alot of time to work on it.
1. I had to change the outdrive with a rebuilt unit to get it in the water, its from a 5.0 engine, slightly different gear ratio, 1.5:1 vs 1.41:1 original as far as I can tell.
2. It has an automotive MSD HEI distributor, curve unknown. I did get a proper marine unit, didn't install yet.
3. I do get full wide open throttle. Flame arrestor is clean, and I do get correct RPM range
4. Bottom is not fouled, no visable damage or hook, handles well on plane.
Head gaskets had been changed before I bought it, compression unknown.
Any input appreciated.
Out of the water for the winter, but may as well start thinking about it. Big problem is a friend, who is an engine builder, is offering to sell me a 375 hp marine smallblock 383, very tempting. Would cruise nice at 25
I have a 1988 245 Vista OMC 260 Cobra. Main question is what speed should I expect WOT and cruise. Info I can find says the boat tops out at 39mph, which I'm guessing is optomistic, but I'm not even close, although RPM is in range. Looking for some real world speed numbers of similar boats.
First time owning a boat this heavy, had 21 ft Sylvan 140 I/O and 22 foot Trophy 260 I/O in the past. I know it's not a speed boat, its a big pointy floating camper, so I'm not expecting to pop skiers up. Had it in the water this summer, fix as I go. No real issues except vcan't get more than 10 gallons of gas in the 70 gallon tank, but that's another story
So engine runs well, runs up to 4300 rpm WOT, but I cant get over about 25 mph (GPS and speedo ) flat water with 2 people, minimal fuel and not much stuff onboard. Fresh cold water, 450 ft above sea level. (Seneca Lake NY) Needs the tabs to get out of the hole, not a surprise. If I trim drive up once it tops out and tabs are up, doesn't add much speed or RPM, starts to porpise, then prop ventilates. Trimmed out, it falls off plane if I drop below 3700. If I add 3 more people in the back, can barley get up on plane at all.
I'm using a Hustler 15x15 4 blade, worlds better than the 15.5x15 omc 3 blade which was listed as stock.
What might be wrong and what I verified. Didn't get alot of time to work on it.
1. I had to change the outdrive with a rebuilt unit to get it in the water, its from a 5.0 engine, slightly different gear ratio, 1.5:1 vs 1.41:1 original as far as I can tell.
2. It has an automotive MSD HEI distributor, curve unknown. I did get a proper marine unit, didn't install yet.
3. I do get full wide open throttle. Flame arrestor is clean, and I do get correct RPM range
4. Bottom is not fouled, no visable damage or hook, handles well on plane.
Head gaskets had been changed before I bought it, compression unknown.
Any input appreciated.
Out of the water for the winter, but may as well start thinking about it. Big problem is a friend, who is an engine builder, is offering to sell me a 375 hp marine smallblock 383, very tempting. Would cruise nice at 25