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+--- Thread: 2000 3500 open with 7.4L 350hp - general questions (/showthread.php?tid=7150)
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2000 3500 open with 7.4L 350hp - general questions - polarbill1999 - 10-05-2020
Hi, my father is looking at a 2000 3500 with what is listed as 350hp Crusader 7.4L. It looks like they say MPI.
- I couldn't find any information online about 2000ish Crusader 7.4L MPIs at 350hp.
- Are these common motors in Tiara?
- Overall thoughts/reliability of these motors?
- Does anybody have an idea of how to find info on these 350hp MPIs? Best I could tell is that most 7.4L were 320hp but couldn't find much of anything on 350hp or more out of the 454.
- It sounds like 8.1s or diesels (they came from 3208 375hp cats) are more desirable for the 3500 but does anybody have direct experience with a 3500 with these (looking at some others online it kind of seems like this was a standard motor). My father doesn't care about cruising at 20+ knots really and actually prefers something more like 12-14.
- Can Tiara 3500s with gassers cruise even somewhat efficiently if not on full plane?
Here is a pic of the motors on the boat in question.
[attachment=725]
RE: 2000 3500 open with 7.4L 350hp - general questions - Capt. Paul - 10-05-2020
Hello,
I have the 320 horse versions in my 2900. 800 hours and no issues. These are essentially the GM 454 truck motors and are well under 1 HP per cubic inch. With proper maintenance, it is not unreasonable to expect 3,000 plus hours of service, if you don't run the balls off them.
I cruise mine at 3200 rpm. Be sure you can make rated WOT on these. You don't want to over load them.
Regards,
Paul
RE: 2000 3500 open with 7.4L 350hp - general questions - Ridin'High - 10-05-2020
I owned a 2000 35 Open with the 7.4 MPI 350hp crusaders. The engines were all that was offered in gas a version from 1998 through 2000. The engines were very reliable. Performance was pretty good, with a 25 - 26 MPH cruise at 3400 RPM and .8 mpg fuel consumption. This is with 4 blade props. A friend of mine now owns the boat and loves it and has had no issues. Good Luck Tom
RE: 2000 3500 open with 7.4L 350hp - general questions - polarbill1999 - 10-05-2020
(10-05-2020, 05:28 PM)Ridin'High Wrote: I owned a 2000 35 Open with the 7.4 MPI 350hp crusaders. The engines were all that was offered in gas a version from 1998 through 2000. The engines were very reliable. Performance was pretty good, with a 25 - 26 MPH cruise at 3400 RPM and .8 mpg fuel consumption. This is with 4 blade props. A friend of mine now owns the boat and loves it and has had no issues. Good Luck Tom
Thank you for your thoughts on the exact setup. This is helpful. I was a bit worried after reading other threads about 8.1 vs 7.4.
Do you by chance have any info on what model/version these motors were. I can't seem to find anything online on 7.4L MPI 350hp Crusaders.
RE: 2000 3500 open with 7.4L 350hp - general questions - Ridin'High - 10-06-2020
I was able to find the owners manual online. Try searching Crusader 7.4 MPI marine engines.
RE: 2000 3500 open with 7.4L 350hp - general questions - polarbill1999 - 10-19-2020
the Survey of the boat went well. The boat was very clean it sounds like. My father says it ran about 14.5 knots at 1700-1800 rpm and if they bumped up to 2100-2200 it ran 17-18 knots. They thought it topped out right around 24-25 knots and max RPM was about 4200. Does all that sound about right?
From what I found online those engines should max out at 4400-4600. Is that right? Does it sound like this boat could be over propped?
2000 3500 open with 7.4L 350hp - general questions - Misdirection - 10-19-2020
WOT should be in the 4400 to 4600 range and the top end a little higher than their suggestion. But if they didnt run the boat to WOT, their just guessing.
However, if they didnt run the boat up to 3200 to 3400, which should be the optimal cruise, I'd ask why not and insist that they go back out and run it to there, and up to WOT if the conditions permitted it.
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RE: 2000 3500 open with 7.4L 350hp - general questions - polarbill1999 - 10-19-2020
(10-19-2020, 06:07 PM)Misdirection Wrote: WOT should be in the 4400 to 4600 range and the top end a little higher than their suggestion. But if they didnt run the boat to WOT, their just guessing.
However, if they didnt run the boat up to 3200 to 3400, which should be the optimal cruise, I'd ask why not and insist that they go back out and run it to there, and up to WOT if the conditions permitted it.
Sent from my SM-A505U using Tapatalk
Thanks, My dad said they ran it up WOT or what they thought was WOT. The boat was full of fuel, has an inflatable on a davit system on the swim platform as well as a 3000 watt generator on the platform (so probably 400-500 pounds I would guess).
I am sure they ran through the 3000-3400 range but my dad mostly noticed that there was a big step up in speed between 1700-1800 rpm (at 14 knots) to 2100 rpm (at 17-18 knots). I am guessing my father will be much more interested in cruising at 18-19 knots then 22-23 knots.
Another thing the surveyor said was that the props seemed small (so not overpropped) but seemed to have more pitch and were cupped. The surveyor expected the props to be more square (ex: 17x17 although I am making up that number) but these must have had a higher pitch.
I have let him know that 4200 seems a little low for WOT. Sounds like he is planning on buying it but would be nice to find the right props eventually. It doesn't sound like things are so out of whack that it is likely they caused harm.
2000 3500 open with 7.4L 350hp - general questions - Misdirection - 10-19-2020
He can contact Tiara customer service and provide them the Hull ID, and Tiara can let him know what props were on the boat when it left the factory. Having the proper props will lead to a longer engine life.
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RE: 2000 3500 open with 7.4L 350hp - general questions - Ridin'High - 10-20-2020
The stock props that I had on my 2000 35 open with 7,4 MPIs were 21D X 23P 3 blade. I upgraded to 21D X 22P 4 blades. Was worth the money, picked up about 1.5 MHP