Pardon my ignorance, but what are "228s"?

Jeff

I will post even though my boat is different, I am hoping to hear from others with my, or similiar combinations in this thread as well.

I rarely go for a ride that I do not open it up wide open to see what she will do on that given day, it is intresting to see the the variables come into play but from this habit I can tell you my boat is over proped right now with 19x22 4 blades as I only get 3500 to 3700 rpm.

My full fuel and water with 5 adults on board in calm, no current water and clean bottom is giving me 33 mph GPS @ 3600 rpms out of the 330hp 440ci. engines in a 39 sedan. I get 150 rpms and 2 mph extra with 2 people and low fuel.

I think by myself with <20% fuel and no water on board I could see 36 mph GPS right now.

My boat has not had any general tuneup parts in nearly a decade because I recently purchased it and has just come out of 7 years of dry heated storage. I have got fresh fuel now and all the fluids have been changed. I am a motorhead so it is going to go faster in due time. I want 40+ out of her so an ultra slick bottom job and some motor pump up work is in her future plans for this fall and winter.

Doug...

I've seen 33mph on the GPS while going downhill. Wind at the back, surfing down waves.

Usually 32.xx or 31.xx depending on trim and fuel.
Turn around 4,400 - 4,600.
I think props are 16x16.
Bridge sedan with 360's.

-K

I have seen 6 and 7 mph reductions in speed on my 46 Bertram with diesels and my buddies 38 Chris Craft wood lapstrake Corinthian with 427 fords with dirty bottoms -vs- clean fresh bottoms.

You (and others with twin engines) might try this little test: At a cruising speed (of say, 2,500 rpms) open ONE throttle all the way and note the rpms achieved, then return to 2,500 rpms. Next, do the other engine the same way and compare. If the two readings are similar, then that's all she'll do. But if one is way lower (several hundred rpms) then you need to look into THAT motor. (This test assumes the tachs are reasonably accurate, which can be checked by the synchronizer and by your ear while cruising.)

Here's the deal, and it's far from obvious: A weak engine will pull down the speed of BOTH engines, though it won't appear that way at the time. The strong engine will make only a few more rpms as it struggles to do more than half of the work.

I run the above test every year to keep track of what's going on down there, and I found a bad plug on one of the motors thanks to it. The motor ran fine at cruising speed, but no doubt it was using more gas because of that plug.

Jeff

Though I would not expect to find them in a Big . In the late 70's early 80's Mercruiser called their 305 4 brl "228" so there is such a thing. I had one in my 1978 F25 Trojan .

Ran her up this evening and left it there until the top end leveled out. Both engines bounced around 4060-4080. It takes a few seconds to work up to those numbers. Usually top out at 4040, 4030 or so and then slowly work up and bounce around.
I could only get 31.2 mph.
Full fuel and I did have the bow down to compensate for the fuel load. Boats been sitting at the dock for a month too.

-Karl

PS. I followed a twin sportsman on trailer down the road this afternoon. I have always wondered how fast those could go. Don't see many twin sportsmans. I like that 36mph. Bet thats a fun ride!

Thanks guys I'll try Jeff's suggestion and see if there is another issue with the boat . I'll let you know what I find.

Bob

rOCKIT HAS A 28 WITH TWINS, i WAS ON IT, VERY FAST BUT HE DIDIN'T OPEN IT UP

Let down again ONLY 2500 RPMS

Since I've owned my big m...(second season) I've never been able to get full RPMs out of her.

I put new carbs on her a few months ago (had strong fuel smell in cabin..problem solved)...as Collin said, I did check rigging of cables to carb...carb is opening to full limit. Choke is wide open. Let down again...new fuel filters installed.

Put new Pertronix distributors and timed 5 deg btdc, 25 total advance this weekend thinking that was the main reason I couldn't reach full rpms (springs were broken,and everything corroded. Can't believe the engine ran so good with broken springs because at idle it was running at 20 deg advance.

Hit the lake for a test run...can't get more than 2500 rpms ...thought well maybe my tachs aren't reading right since I changed the voltage input to them from 9.7v to 13v (not sure how the tachs work), the snap on high tech timing gun I used has rpm reading and it agrees with my tachs...so it's not the tachs. I'm getting a max speed of 19 knots/22mph at a max of 2500 rpms. That's about the correct speed for 2500 rpms I think so my tachs must be correct.

All tuned up! New wires, plugs....everything!

So now what? Only thing left are the props and I don't know what type props I have on her. Had her pulled several months ago and didn't check them This is all new to me and I have taken a lot for granted (like the correct props were installed! ) I've learned a lot, thanks to you guys. I guess when the water gets warm enough, I'll put on a dive mask and see if I can see any stamps on the props. If I can't see a stamp, I may do an in the water prop removal

I'm getting bummed out because my pockets are only so deep and every time I turn around it's another $1000...and that's doing all the labor myself. I keep telling myself it's better than depreciation on a shiny plastic boat

Questions are:

Do you think my tachs are reading correct with the new coil and distributors?
(not sure about their input, 13v vs 9.7v input on coil, rpm/speed seems correct to me 2500rpms/19kts/22mph. tachs check against Snap ON timing gun reading)

Do you think the same bozo mech that put the fake sheet metal anodes on could have put props that wrong on her? (already know the answer)

With a so so bottom and trim tabs all the way down (to keep nose down), full tank...I should only be giving up 500 rpms at the most...agreed?

[b]I'm thinking the pitch on the props are bad wrong...what do you guys think?

Bummed out and looking for 1500 more rpms!