repower or not to repower

[ShipPilot]

How goes it everyone? I am hoping I could draw on everyone's experience.

I am running a 03' with the standard 150 HPDI. I have never been exactly thrilled on the top end speed with this setup. I have a collapsible tower on the boat which does create some significant sail area but with WOT end I am only making maybe 22-25 kts at about 3800-4200 rpms depending how I have her trimmed with the tabs. Now I have had this motor tested and it comes back with zero codes and have had my throttle adjusted to ensure I am getting full range and injectors opening fully at the top end. I am meticulous with filters and fuel system. Initially I was concerned I wasn't propped right but in considering the top end rpms I am getting I don't know. I will say I typically run with 2-3 people around st Petersburg fl and I carry more fuel than I need usually about 75% of that 93 gallon tank. So can you help a brother out?

Any 21SE owners with 150 hpdi's out there what are you guys getting on the top end?

what are your recommendations?

I am thinking about repowering with a quality used 200 hp two stroke. I have been offered an older Ox66 with known and trusted maintenance record at basically what I can trade the 150 in for. Or always looking for 200 hp deals out there.

I have the cash to repower but it seems like everyone I have talked to is really happy with a 21se and 150. So please educate me!

all the best and tight lines!

 

[DaleH]

Parkers are not and have never been 'speed demons'. I would think up to 25 kt cruise on an SE hull would be ideal! That hull can't go faster in any sea anyway, even with a 300hp on the stern. I'd stay with what you have and save your $$ ...

 

[Megabyte]

The fire department that I retired from had a pair of Parker 21SE rescue boats.
One had a 225 hp Merc on the back, the other a 150 HPDI.
Both had t-tops, full electronics, fire suppression and medical gear on board.

The difference in top speed at WOT between the two boats was 2 knots.

As Dale said, these hulls have a terminal speed that no amount of horsepower you hang on them can overcome.
These boats are not Contenders, Regulators, or SeaVee's.
They are damm rugged fishing boats.

 

[ShipPilot]

Thanks Gents,

I really appreciate the reassurance. I love this boat it gets skinny enough to use in the flats but still can handle the slop.

 

[windknotnc]

Your speed is correct with that weight and RPM however it sounds like you are over propped. At WOT and trimmed with 1/2 tank of gas and 2 people you should have another 1000rpm. What pitch prop are you running? On that hull every 2" of pitch you go down should gain you about 400rpm. With the heavy load you probably need a 15 -17 pitch. How is the hole shot on the boat? If propped right it should come out of the water quickly and be most efficient in the 4000-4300 rpm range. This would also not be WOT.

 

[Brad 21se]

I'm running a 15 pitch, 3-blade SS prop on mine. 5400rpm WOT doing about 40mph. I typically head out to fish cruising around 3700rpm at about 26mph or so. The hull seems to like that speed with a little tab down getting over 3MPG.

 

[DaleH]

Agreed, sorry I missed it ... but while your HP might be ideal, without knowing what RPMs you can turn at WOT and what the motor is rated for (5,500 or 6,000 max) ... we can't tell if you have the right pitch prop. Ideally you'd want to be setup so you are no more than 200 RPMs maximum, with typical gear carried, 1/3-1/2 fuel and you.

Boats only get heavier as the season progresses ... bottom gets fouled, motors lose another 10% in power in hot temps, and more gear accumulates on board ...

 

[Megabyte]

It would also be helpful to know the mounted height of your motor.
Most companies and dealers have a tendency to mount the motor way too low which kills performance.

When I bought my boat, the motor was buried down to the last hole.
2 years ago I had it raised 2 holes, and honestly it could have been raised all the way up.
Did it help? Oh hell yes. :wink:

 

[ShipPilot]

All Great info and really appreciate it,

When I get down to the boat I will check the prop pitch. I am kind of embarrassed I don't know that off the top of my head.... I do know it is an aftermarket prop previous owner changed it out and I have the original prop sold with the motor.

Hole shot is pretty slow to be honest but I attributed that to 3 guys and 75% fuel. As for motor height I am considering a jack plate but that was more due to the fact I fish St Petersburg inshore waters which tend to get skinny on the ride home with a falling tide.

 

[ShipPilot]

Update:

I am running a correct pitched prop.... check
Compression good...... check
number one cylinder ...... bad spark plug and fouled 02 sensor... a couple hours running on ring free and new plug..... getting better
Number 2 cylinder not firing either I think it is probably fouled or bad injector.... getting better


bottom line 22-25kts on 4/6 cylinders not so shabby. going to be a whole different engine by the time I am done.

I appreciate everyone's help though.

 

[Brad 21se]

Check your injector drivers......

I went through that issue on a previous boat with a HPDI - low rpm's at WOT. Check the plug on the non-firing cylinder to see if it still looks new. If you need a new driver, PM me. I still have one since I bought a pair when I was chasing my issues. They are crazy $$$ new.