Slow Mako?

[JD Burch]

1978 23'cc, 1999 225 Suzuki EFI, t-top(w/electonics box), ~100gals. gas, 310lbs people (no, not just me).

At 4200 rpm, I'm only getting about 24-25kts and having trouble staying on plane (10-12gph). At 4800 rpm (which the engine seems to be very happy with), I get about 28-29 kts (15-18 gph) depending on conditions and a real nice plane.

The other night, pretty flat conditions, was at ~5200 rpms and got to about 34kts (before I had to slow down at the no wake zone). Speed was still coming up slowly, but I didn't feel like there was a lot of engine left at all. I don't think it was going to get more than 37-38 kts or so - unless top end speed comes on a lot slower than I thought.

After hearing about all the 45-50+ knot boats (incl. some of similar size and power), what's my problem? I have no idea what the dimensions are on the prop - boat is a recent purchase - but its SS and in great shape. Is my engine weak? It seems to be running really nicely, just not lot of power. The trim tabs haven't been working until recently so I'm just figuring them out.

Are these specs fairly normal or am I slow? BTW - All speeds GPS.

Thanks. Jim

[Hugs Tug]

You really need to see what the prop size is. From what I understand the Suzuki engines use a different configuration on sizing. Wart will be a great influence on sizing. As far as the T-Top is concerned, do you have the 3 peice enclosure that goes around it? This will definitely slow you down. How is the compression on the engine?

[inkahootz]

Your numbers sound pretty good to me.

I have to run 4500rpm to get 25 knots. Flat out I get 35 knots, but I don't remember the rpm's, I only did it once to make sure the boat was propped ok. It was running in whatever range the owners manual specked for wfo.

I don't know what my fuel numbers were and I really didn't want to[:u]

(Johnson 225 carbed)

[mako224]

Numbers don't sound bad to me. Trim of the motor and trim tab position have a huge affect on speed. You will also go faster on water that has a slight chop than you will on slick calm water. Were you running with or against the tide?

[mako224]

Don't believe all the speed numbers you read. Note: there is a pretty significant differance between 50 Kn/hour and 50 MPH.

50 kn/hour = about 58 mph

1 nauticle mile = 1.15 statutory miles

What differance does it make anyway when none of these boats run comfortably above 24 kn/hour in choppy seas anyway.

[Trident]

Hi there-

i have the same engine (1998 Suzuki 225EFI) on my 1991 Mako 231. At 5200 RPMS (WOT) I top out at about 42-43mph....however my mechanic says that the boat is over propped and I need to swap in a smaller prop so that I turn 5500-5700RPMS. He also said that because I am over propped...I am not even hitting the powerband.

How's your engine treated you? Mine has been very, very reliable (knock on wood). It is a kinda funny motor because it has 12 spark plugs and also because it drops a cylinder below as certain RPM and causes some vibrations...

[Trident]

What size prop are you running?

I believe mine is 14 1/4 x 20....and I need to move down to 14 1/4 x 18.

-Ed-

[JD Burch]

No idea what size my prop is, I keep forgetting to ask my mechanic when he has the boat - which has not been for the engine (engine has been great so far). The specs for the older suzuki's list a few options, and I didn't own it when the engine was put on, so I don't know which was chosen. Is there any way to tell prop size by looking or measuring?

I actually have no problem with the way the boat runs, just seems slow compared to some of the others on the board.

I'll have to do a real WOT run and let it top out to see. I don't think I'll see more than 5200-5300, so maybe I'm over-propped also.

Ed, what's your cruise rpm/speed?

Jim

[ktugboat42]

If you check this post http://www.classicmako.com/forum/top...?TOPIC_ID=4616 you'll see that your #'s are close to everyone else's. I put your #'s in.

[Trident]

Jim-

The prop size will be stamped inside the hub. You'll need to take off the prop to find it.

Honestly, I don't know what my cruise speed is!! I normally just put it in gear and go. One of these days, I'd like to get a NAVMAN to see what my fuel efficiency is.

If you are only turning 5200 rpm at WOT, I would definitely say that you are over propped too....

[BYRAM]

jim, where do you keep your boat in port chester ?? up the byram river ? i'm at byram shore town marina. didn't mean to derail your thread, just curious as you are local.

[classic73mako]

Another thing that can slow you way down and make the boat feel like it's wallowing is marine growth on the bottom. Even a few dozen barnicals will make the boat handel like it can't get out of it's own way and top speed it where you will see it the most. Unless your sure that this is not the case, I would start there and then go on to the prop size / pitch.

Mike

[Justin]

quote:

---

Originally posted by JD Burch


1978 23'cc, 1999 225 Suzuki EFI, t-top(w/electonics box), ~100gals. gas, 310lbs people (no, not just me).

At 4200 rpm, I'm only getting about 24-25kts and having trouble staying on plane (10-12gph). At 4800 rpm (which the engine seems to be very happy with), I get about 28-29 kts (15-18 gph) depending on conditions and a real nice plane.

The other night, pretty flat conditions, was at ~5200 rpms and got to about 34kts (before I had to slow down at the no wake zone). Speed was still coming up slowly, but I didn't feel like there was a lot of engine left at all. I don't think it was going to get more than 37-38 kts or so - unless top end speed comes on a lot slower than I thought.

After hearing about all the 45-50+ knot boats (incl. some of similar size and power), what's my problem? I have no idea what the dimensions are on the prop - boat is a recent purchase - but its SS and in great shape. Is my engine weak? It seems to be running really nicely, just not lot of power. The trim tabs haven't been working until recently so I'm just figuring them out.

Are these specs fairly normal or am I slow? BTW - All speeds GPS.

Thanks. Jim

---

I have the same hull, with a 1994 225 Rude, and I'm getting very similar numbers given a similar load size(which disappoints slightly).

At 4500RPM, I am getting about 28mph, and WOT @ 5500-700RPM sees about 35-38mph.

I am running a 15x17 aluminum prop...does that seem right, or should I switch?

[Joe N]

i've got a 232 w a 225 Merch. your numbers sound a little slow to me too.

At 4200 rpms, i'm easily on plane and stay on plane down to 3200 3400 rpms with the tabs down. yes its sluggist but i'm out of the water. at 4200, i'm 28 - 30 mph. wot is 5500 - 5600 rpms and 43 - 43 mph. but thats flat water and jst me (170 pounds) and trimmed perfectly (as perfectly as this porpoisely predisposed can be trimmed).

[JD Burch]

Update: previous #'s are accurate. Friday night fishing, 4 guys, pretty flat conditions yielded 5200 wot @ 34 kts. I think I'm propped wrong, but I'm in no hurry to change it, I'm okay running in the mid 4000s between 24-28kts. Will look into new prop for next year.

Jim