Mercruiser 228 Underpowered?

[nwc09121986]

I have a 1989 OV with a V8 Mercruiser 228 in it, the prop that came on it was a 15-1/4x15 it tops out at 19 and over revs terribly to the tune of around 5800rpm, I want to change props and hope to bring the top end up to around 25-28 is that possible? And what size prop should be on this?

 

[Kameroo]

22' boat with a V8? That thing should do mid-40's at least. I'd suggest check the prop chart on the Sea Ray website (if they still have it posted). Otherwise, there's bound to be a few people here with a similar set-up.

 

[nwc09121986]

Thats what I thought, the 1989 220 is a 23'8" boat but still feel like 30 is reasonable? I was also wondering if this could be a problem with the lower unit gearing? If that is a possibility how do I find that out and how do I remedy it?

 

[ghuskin]

you should be able to at least get 27 - 33 under ideal conditions. and yes, the 228 is underpowered. IMHO

 

[berth control]

I think you have a spun hub in your prop. If it's rubber you need to have a new one pressed in, if it's the square plastic block design you can just get one from the local boat store. If you are hitting WOT of that many r's at that speed with that prop, something is slipping and the prop hub is likely the one thing that could slip like that and not make lots of smoke or grinding noise. Check it out and let us know. Once you get it fixed, your boat should run around 40mph. I don't think that engine is underpowered for that boat. Maybe not a beast, but you should have no trouble getting on plane and cruising around 30mph with a load of people in with that engine.

 

[ghuskin]

I'm 34 WOT (SOG per GPS) with clean bottom, calm water, 2 persons in boat. 15 x 17 3 blade prop. I'd love to hit 40 and cruise @ 30

 

[nwc09121986]

I am changing props today to a 15.25x19 and see how that goes, I am also going to manually turn the engine over and see how many revolutions the prop does and see if the gearing is correct. What ratio am I looking for?

 

[nwc09121986]

One more thing, the original engine was a V6 and the owner previous changed to a V8 without changing the tachometer, will this affect the reading of the tachometer and if so how much?

 

[berth control]

I'm 34 WOT (SOG per GPS) with clean bottom, calm water, 2 persons in boat. 15 x 17 3 blade prop. I'd love to hit 40 and cruise @ 30

What's you'r wot rpm? It just seems too slow for that boat and engine, but it may be heavier than others and I could be wrong. My buddy has a four winns 23 with a ford 351 and it goes 50, my dad has a 18 foot crownline with a 4.3 and it goes 50, my old weekender was a heavy 23 footer with a 260 (5.7 litre) and it would go 40 and cruise at 30 all day. I know those other boats are not the same, but I would say similar engine to size ratios.

Again, I could be all wrong. Just my feeling though.:smt101

 

[berth control]

I am changing props today to a 15.25x19 and see how that goes, I am also going to manually turn the engine over and see how many revolutions the prop does and see if the gearing is correct. What ratio am I looking for?

I would guess the new prop will make a huge difference, because it will come with a new hub. The rpm's of the prop while the engine is turning over will be really tough to read and make any sense of. I would just look at the sea ray prop chart and it will tell you the drive ratio.

 

[nwc09121986]

Here is the update! I found out that the guys that changed motors didn't change the tachometer, so all of my readdings have been off. I changed the tach to the V8 setting and now when I run with a 15.25x15 prop I can run the RPM's all the way up to 4200 and am going 32 with more to give on the top end, so I think I am going to go to the 15.25x17 or 16x16 any suggestions?

 

[berth control]

Glad to hear you got it figured out! I would think you could go a little steeper if you still have throttle left on the top end.